U.S. patent application number 14/887095 was filed with the patent office on 2016-02-11 for method and system for storing inventory holders.
The applicant listed for this patent is Amazon Technologies, Inc.. Invention is credited to Michael C. Mountz, Peter R. Wurman.
Application Number | 20160042314 14/887095 |
Document ID | / |
Family ID | 37678154 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160042314 |
Kind Code |
A1 |
Mountz; Michael C. ; et
al. |
February 11, 2016 |
METHOD AND SYSTEM FOR STORING INVENTORY HOLDERS
Abstract
A method for storing inventory items in an inventory system
includes detecting that an inventory holder is available for
storage and determining a classification of the inventory holder.
The method also includes determining a classification of each of a
plurality of storage locations and selecting a storage location for
the inventory holder based, at least in part, on the classification
of the inventory holder and the classification of the selected
storage location. The method additionally includes transmitting
information identifying the storage location to a mobile drive unit
associated with the inventory holder.
Inventors: |
Mountz; Michael C.;
(Cambridge, MA) ; Wurman; Peter R.; (Raleigh,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Amazon Technologies, Inc. |
Reno |
NV |
US |
|
|
Family ID: |
37678154 |
Appl. No.: |
14/887095 |
Filed: |
October 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11185467 |
Jul 19, 2005 |
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14887095 |
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Current U.S.
Class: |
705/28 |
Current CPC
Class: |
G08C 17/02 20130101;
G06Q 10/087 20130101 |
International
Class: |
G06Q 10/08 20060101
G06Q010/08; G08C 17/02 20060101 G08C017/02 |
Claims
1-43. (canceled)
44. A system comprising: a management module configured to control
and administer order fulfilment operations within a workspace; and
a robotic transport unit that is remote from the management module,
the robotic transport unit comprising a self-propelled device that
is operable to wirelessly receive and respond to commands from the
management module to retrieve and transport one or more inventory
shelves to one or more locations designated by the management
module within the workspace.
45. The system of claim 44, wherein the management module is
further configured to fulfill orders for inventory items stored by
the one or more inventory shelves by transmitting one or more
wireless commands to the robotic transport unit.
46. The system of claim 44, wherein one or more wireless commands
transmitted by the management module identify a first inventory
shelf that stores a first inventory item requested by a first
order.
47. The system of claim 44, wherein one or more wireless commands
transmitted by the management module identify to the robotic
transport unit a location of the one or more inventory shelves and
facilitate navigation by the robotic transport unit to the one or
more inventory shelves.
48. The system of claim 44, wherein the management module
coordinates fulfillment of an order comprising a plurality of
inventory items by instructing one or more robotic transport units
to transport, in succession, a plurality of inventory shelves that
store the plurality of inventory items to the one or more
designated locations.
49. The system of claim 44, wherein the management module is
further configured to transmit instructions to the robotic
transport unit to transport the one or more inventory shelves to a
storage location in the workspace, the storage location being
selected by the management module based at least in part on the
frequency with which inventory items stored by the one or more
inventory shelves are requested by the order fulfilment
operations.
50. The system of claim 44, wherein the management module selects
the robotic transport unit from a plurality of available robotic
transport units for carrying out particular order fulfillment
operations based at least in part on one or more metrics associated
with the plurality of robotic transport units, the robotic
transport unit being selected based on a first metric being less
than at least a second metric associated with another of the
plurality of available robotic transport units.
51. The system of claim 44, wherein the management module, upon
instructing the robotic transport unit to retrieve an inventory
shelf, initiates a docking operation by which the robotic transport
unit moves beneath the inventory shelf and actuates a docking
mechanism that initiates contact with at least a portion of the
inventory shelf.
52. A method comprising: receiving, by a management module, an
order comprising a first inventory item and a second inventory
item; locating, by the management module, inside a workspace a
first inventory shelf storing the first inventory item and a second
inventory shelf storing the second inventory item; wirelessly
transmitting, from the management module to a first robotic
transport unit, one or more first instructions, to retrieve the
first inventory shelf and transport the first inventory shelf to an
order fulfillment location; and wirelessly transmitting, from the
management module to a second robotic transport unit, one or more
second instructions to retrieve the second inventory shelf and
transport the second inventory shelf to the order fulfillment
location; wherein the management module determines the one or more
first instructions and the one or more second instructions such
that the first robotic transport unit delivers the first inventory
shelf at a first time to the order fulfilment location and the
second robotic transport unit successively delivers the second
inventory shelf at a second time after the first time to the order
fulfilment location.
53. The method of claim 52, further comprising transmitting, from
the management module to the order fulfillment location, one or
more third instructions to retrieve the first inventory item from
the first inventory shelf and to retrieve the second inventory item
from the second inventory shelf.
54. The method of claim 52, wherein the one or more first
instructions comprise a location of the first inventory shelf and
information to facilitate navigation of the first robotic transport
unit to the first inventory shelf.
55. The method of claim 52, further comprising selecting, by the
management module, the first robotic transport unit to retrieve the
first inventory shelf based on one or more metrics associated with
the first robotic transport unit and the second robotic transport
unit, the first robotic transport unit being selected based on a
first metric being less than at least a second metric associated
with the second robotic transport unit.
56. The method of claim 52, further comprising selecting, by the
management module, the first inventory shelf from a plurality of
inventory shelves storing the first inventory item, the first
inventory shelf being selected based on a first metric being less
than at least a second metric associated with another inventory
shelf of the plurality of inventory shelves.
57. The method of claim 52, further comprising selecting, by the
management module, the order fulfillment location from a plurality
of order fulfilment locations, the order fulfillment location being
selected based on a first metric being less than at least a second
metric associated with another order fulfilment location of the
plurality of order fulfilment locations.
58. The method of claim 52, further comprising selecting, by the
management module, the first robotic transport unit for retrieving
the first inventory shelf based on whether the first robotic
transport unit is already traveling to the first inventory
shelf.
59. A system comprising: a first robotic transport unit; a second
robotic transport unit; a management module configured to fulfill
an order comprising a first inventory item and a second inventory
item by issuing at least a first instruction to the first robotic
transport unit and at least a second instruction to the second
robotic transport unit in a workspace; wherein the first robotic
transport unit is operable to, in response to receiving the at
least first instruction, initiate retrieval of a first inventory
shelf storing the first inventory item and transport the first
inventory shelf to an order fulfilment station in the workspace at
a first time; and wherein the second robotic transport unit is
operable to, in response to receiving the at least second
instruction, initiate retrieval of a second inventory shelf storing
the second inventory item and transport the second inventory shelf
to the order fulfilment station in the workspace at a second time,
wherein the first and second robotic transport units arrive in
succession at the order fulfilment station at the first and second
times.
60. The system of claim 59, wherein the management module is
further operable to send at least a third instruction to the order
fulfilment station identifying that the order comprises the first
inventory item and the second inventory item.
61. The system of claim 60, wherein the management module is
further configured to determine the at least first instruction and
at least second instruction to cause the first and second robotic
transport units to arrive successively at the order fulfilment
station and wherein the at least third instruction further
identifies that the first inventory item is stored on the first
inventory shelf and the second inventory item is stored on the
second inventory shelf.
62. The system of claim 59, wherein the first robotic transport
unit, upon arriving at the first inventory shelf, initiates a
docking operation by which the first robotic transport unit moves a
center of gravity of the first robotic transport unit beneath the
first inventory shelf and actuates a docking mechanism that
initiates contact with at least a portion of the first inventory
shelf, wherein the center of gravity of the first robotic transport
unit is aligned substantially with the center of gravity of the
first inventory shelf.
63. The system of claim 59, wherein the first inventory shelf is
associated with a storage location and the management module is
further operable to initiate retrieval of the first inventory shelf
based on whether the first inventory shelf is stored at the
associated storage location.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] This invention relates in general to inventory systems, and
more particularly to a method and system for efficient storage and
retrieval of inventory items.
BACKGROUND OF THE INVENTION
[0002] Modern inventory systems, such as those in mail-order
warehouses, airport luggage systems, and custom-order manufacturing
facilities, face significant challenges in responding to requests
for inventory items. In inventory systems tasked with responding to
large numbers of diverse inventory requests, slow responses to
inventory requests may result in an ever-increasing backlog of
inventory requests. Furthermore, in inventory systems encompassing
substantial amounts of physical space, response times for inventory
requests may depend heavily on the storage spaces of the requested
inventory items within the inventory system.
SUMMARY OF THE INVENTION
[0003] In accordance with the present invention, the disadvantages
and problems associated inventory storage have been substantially
reduced or eliminated. In particular, a mobile inventory system is
provided that includes one or more mobile drive units capable of
moving any of a plurality of inventory holders between locations
within a physical space associated with the mobile inventory
system.
[0004] In accordance with one embodiment of the present invention,
a method for storing inventory items in an inventory system
includes detecting that an inventory holder is available for
storage and determining a classification of the inventory holder.
The method also includes determining a classification of each of a
plurality of storage locations and selecting a storage location for
the inventory holder based, at least in part, on the classification
of the inventory holder and the classification of the selected
storage location. The method additionally includes transmitting
information identifying the storage location to a mobile drive unit
associated with the inventory holder.
[0005] In accordance with another embodiment of the present
invention, a system for storing inventory items, comprises a
plurality of inventory holders, a plurality of mobile drive units,
a plurality of inventory stations, and a management module. The
plurality of inventory holders are capable of storing inventory
items and the plurality of mobile drive units are capable of moving
the inventory holders. The plurality of inventory stations
represent locations where inventory items may be removed from
inventory holders and/or equipment for removing inventory items
from inventory holders. Additionally, the management module is
capable of detecting that an inventory holder is available for
storage and determining a classification of the inventory holder.
The management module is also capable of determining a
classification of each of a plurality of storage locations and
selecting a storage location for the inventory holder based, at
least in part, on the classification of the inventory holder and
the classification of the selected storage location. The management
module is additionally capable of transmitting information
identifying the storage location to a mobile drive unit associated
with the inventory holder.
[0006] Technical advantages of certain embodiments of the present
invention include the ability to optimize, with respect to task
completion times, work distribution, and other relevant metrics,
the selection of system components to perform inventory-related
tasks. Other technical advantages of certain embodiments of the
present invention include providing a flexible and scalable
inventory storage solution that can be easily adapted to
accommodate system growth and modification. Other technical
advantages of the present invention will be readily apparent to one
skilled in the art from the following figures, descriptions, and
claims. Moreover, while specific advantages have been enumerated
above, various embodiments may include all, some, or none of the
enumerated advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a more complete understanding of the present invention
and its advantages, reference is now made to the following
description, taken in conjunction with the accompanying drawings,
in which:
[0008] FIG. 1 illustrates components of an inventory system
according to a particular embodiment;
[0009] FIG. 2 illustrates operation of a particular embodiment of
the inventory system while retrieving an inventory holder
containing particular inventory items;
[0010] FIG. 3 illustrates operation of a particular embodiment of
the inventory system while storing the inventory holder;
[0011] FIG. 4 illustrates operation of a particular embodiment of
the inventory system while replenishing the inventory holder;
[0012] FIG. 5 is a flowchart illustrating operation of a particular
embodiment of the inventory system while retrieving the inventory
holder;
[0013] FIG. 6 is a flowchart illustrating operation of a particular
embodiment of the inventory system while storing the inventory
holder; and
[0014] FIG. 7 is a flowchart illustrating operation of a particular
embodiment of the inventory system while replenishing the inventory
holder.
DETAILED DESCRIPTION OF THE INVENTION
[0015] FIG. 1 illustrates the contents of an inventory system 10.
Inventory system 10 includes a management module 15, one or more
mobile drive units 20, one or more inventory holders 30, and one or
more inventory stations 50. Mobile drive units 20 transport
inventory holders 30 between storage spaces 90 and/or inventory
stations 50 within a workspace 70 in response to commands
communicated by management module 15. Each inventory holder 30
stores one or more types of inventory items 40. As a result,
inventory system 10 is capable of moving inventory items 40 between
storage spaces and inventory stations 50 in order to facilitate the
input and removal of inventory items 40 from inventory system 10
and the completion of other tasks involving inventory items 40.
[0016] Management module 15 receives and/or generates inventory
requests that initiate particular operations involving inventory
items 40 and transmits these inventory requests to appropriate
components of inventory system 10. These inventory requests specify
operations to be performed by inventory system 10 and/or inventory
items 40 that are associated with these operations. Management
module 15 may select components of inventory system 10 to perform
these operations and communicate appropriate commands and/or data
to the selected components to facilitate completion of these
operations. Although the description below focuses on embodiments
of inventory system 10 that receive inventory requests from other
components of inventory system 10, management module 15 may
alternatively or additionally generate inventory requests itself
using any appropriate techniques. In such embodiments, management
module 15 may generate inventory requests based on a predetermined
schedule of operations, in response to detecting the occurrence of
a particular event, or at any appropriate time.
[0017] Additionally, management module 15 may represent a single
component, multiple components located at a central location within
inventory system 10, and/or multiple components distributed
throughout inventory system 10. For example, management module 15
may represent components of one or more mobile drive units 20 that
are capable of communicating information between the mobile drive
units 20 and coordinating movement of mobile drive units 20 in
transporting inventory holders 30. In general, management module 15
may include any appropriate combination of hardware and/or software
suitable to provide the described functionality and may further
include components located on mobile drive units 20, inventory
stations 50, or other elements of inventory system 10.
[0018] Mobile drive units 20 move inventory holders 30 between
locations within a workspace 70 associated with inventory system
10. Mobile drive units 20 may represent any devices or components
appropriate for use in inventory system 10 based on the
characteristics and configuration of inventory holders 30 and/or
other elements of inventory system 10. In a particular embodiment
of inventory system 10, mobile drive units 20 represent
independent, self-powered devices configured to freely move about
workspace 70. In alternative embodiments, mobile drive units 20
represent elements of a tracked inventory system 10 configured to
move inventory holder 30 along tracks, rails, cables, or other
guidance elements traversing workspace 70. In such an embodiment,
mobile drive units 20 may receive power through a connection to the
guidance elements, such as a powered rail.
[0019] Additionally, mobile drive units 20 may be capable of
communicating with management module 15 to receive information
identifying selected inventory holders 30, transmit locations of
mobile drive units 20, or exchange any other suitable information
to be used by management module 15 or mobile drive units 20 during
operation. Mobile drive units 20 may communicate with management
module 15 wirelessly, using wired connections between mobile drive
units 20 and management module 15, and/or in any other appropriate
manner. As one example, particular embodiments of mobile drive unit
20 may communicate with management module 15 and/or with one
another using 802.11, Bluetooth, or any other appropriate wireless
communication protocol. As another example, in a tracked inventory
system 10, tracks or other guidance element upon which mobile drive
units 20 move may be wired to facilitate communication between
mobile drive units 20 and other components of inventory system
10.
[0020] Furthermore, as noted above, management module 15 may
include components of individual mobile drive units 20. Thus, for
the purposes of this description, communication between management
module 15 and a particular mobile drive unit 20 may represent
communication between components of a particular mobile drive unit
20. In general, mobile drive units 20 may be powered, controlled,
and propelled in any manner appropriate based on the configuration
and characteristics of inventory system 10.
[0021] Inventory holders 30 store inventory items 40. In a
particular embodiment, inventory holders 30 include multiple
storage bins with each storage bin capable of holding a different
type of inventory item 40. Inventory holders 30 are capable of
being rolled or otherwise moved by mobile drive units 20. In
particular embodiments, inventory holder 30 may provide additional
propulsion to supplement that provided by mobile drive unit 20 when
moving inventory holder 30.
[0022] Additionally, each inventory holder 30 may include a
plurality of faces, and each bin may be accessible through one or
more faces of the inventory holder 30. For example, in a particular
embodiment, inventory holder 30 includes four faces. In such an
embodiment, bins located at a corner of two faces may be accessible
through either of those two faces, while each of the other bins is
accessible through an opening in one of the four faces. Mobile
drive unit 20 may be configured to rotate inventory holder 30 at
appropriate times to present a particular face and the bins
associated with that face to an operator or other components of
inventory system 10.
[0023] Inventory items 40 represent any objects suitable for
storage and retrieval in an automated inventory system 10. For the
purposes of this description, "inventory item 40" may represent any
one or more objects of a particular type that are stored in
inventory system 10, while a "unit" of an inventory item 40
represents an individual object of that type. For example, in an
inventory system 10 that stores books, a particular book title may
represent an "inventory item 40" while each individual copy of that
book may represent a "unit" of the inventory item 40. Thus, a
particular inventory holder 30 is currently "storing" a particular
inventory item 40 if the inventory holder 30 currently holds one or
more units of that type. Similarly, two units of inventory may
represent the "same" inventory item 40 if the units are of the same
type.
[0024] As noted, inventory items 40 may represent any objects
suitable for storage in inventory system 10. As one example,
inventory system 10 may represent a mail order warehouse facility,
and inventory items 40 may represent merchandise stored in the
warehouse facility. Mobile drive unit 20 may retrieve a particular
inventory holder 30 containing one or more inventory items 40
requested in an order to be packed for delivery to a customer.
[0025] As another example, inventory system 10 may represent an
airport luggage facility. In such an embodiment, inventory items 40
may represent pieces of luggage stored in the luggage facility.
Mobile drive unit 20 may retrieve inventory holder 30 containing
luggage arriving and/or departing on particular flights or luggage
destined for particular types of processing, such as x-ray or
manual searching.
[0026] As another example, inventory system 10 may represent a
merchandise-return facility. In such an embodiment, inventory items
40 may represent merchandise returned by customers. Units of these
inventory items 40 may be stored in inventory holders 30 when
received at the facility. At appropriate times, a large number of
units may be removed from a particular inventory holder 30 and
packed for shipment back to a warehouse or other facility. For
example, individual units of a particular inventory item 40 may be
received and stored in inventory holders 30 until a threshold
number of units of that inventory item 40 have been received. A
pallet may then be packed with inventory item 40 and shipped to
another facility, such as a mail-order warehouse.
[0027] As yet another example, inventory system 10 may represent a
manufacturing facility, and inventory items 40 may represent
individual components of a manufacturing kit. More specifically,
these components may represent components intended for inclusion in
an assembled product, such as electronic components for a
customized computer system. In such an embodiment, inventory system
10 may retrieve particular components identified by a specification
associated with an order for the product so that a customized
version of the product can be built . . . . Although a number of
example embodiments are described, inventory system 10 may, in
general, represent any suitable facility or system for storing and
processing inventory items 40, and inventory items 40 may represent
objects of any type suitable for storage in a particular inventory
system 10.
[0028] Inventory stations 50 represent locations designated for the
removal of inventory items 40 from inventory holders 30, the
introduction of inventory items 40 into inventory holders 30, the
counting of inventory items 40 in inventory holders 30, and/or the
processing or handling of inventory items 40 in any other suitable
manner. Inventory stations 50 may also represent any appropriate
components for processing or handling inventory items 40, such as
scanners for monitoring the flow of inventory items 40 in and out
of inventory system 10, communication interfaces for communicating
with management module 15, and/or any other suitable components.
Inventory stations 50 may be controlled, entirely or in part, by
human operators or may be fully automated. Moreover, the human or
automated operators of inventory stations 50 may be capable of
performing certain tasks to inventory items 40, such as packing or
counting inventory items 40, as part of the operation of inventory
system 10.
[0029] Although "inventory station" as used in the following
description refers to locations at which any appropriate processing
operation supported by inventory system 10 may be completed,
particular embodiments of inventory system 10 may include
specialized inventory stations 50 suitable for performing only a
single processing task supported by inventory system 10. For
example, a particular inventory station 50 may be capable of
handling only retrieval requests or only replenishment requests, as
defined below. Moreover, a particular embodiment of inventory
system 10 may include inventory stations 50 that are, in general,
capable of handling multiple types of inventory requests but, at
any given time, configured to handle only one particular type of
inventory requests.
[0030] Workspace 70 represents an area associated with inventory
system 10 in which mobile drive units 20 can move and/or inventory
holders 30 can be stored. For example, workspace 70 may represent
all or part of the floor of a mail-order warehouse in which
inventory system 10 operates. Although FIG. 1 shows, for the
purposes of illustration, an embodiment of inventory system 10 in
which workspace 70 includes a fixed, predetermined, and finite
physical space, particular embodiments of inventory system 10 may
include mobile drive units 20 and inventory holders 30 that are
configured to operate within a workspace 70 that is of variable
dimensions and/or arbitrary geometry.
[0031] During operation of a particular embodiment of inventory
system 10, management module 15 receives inventory requests that
trigger particular operations within inventory system 10 including,
but not limited to, operations associated with the retrieval,
storage, replenishment, and counting of inventory items 40 and/or
inventory holders 30. Inventory requests may represent
communication of any form suitable for inventory system 10 and may
include any appropriate information identifying inventory items 40
and/or operations to be completed by inventory system 10.
Furthermore, although the description below focuses on an
embodiment of inventory system 10 capable of performing particular
operations, a particular embodiment of inventory system 10 may be
configured to perform any appropriate operation associated with the
storage, processing, or removal of inventory items 40.
[0032] As noted above, management module 15 may receive inventory
requests from a human operator or other components of inventory
system 10. For example, an operator of inventory system 10 may
manually enter inventory requests using a keyboard coupled to
management module 15. As another example, management module 15 may
receive inventory requests from remote components over a network
connection, such as an internet connection. Alternatively,
management module 15 may itself generate inventory requests. For
example, management module 15 may be configured to initiate a
particular operation based on a predetermined schedule or in
response to a particular event, and may generate inventory requests
accordingly. In general, management module 15 may receive or
generate inventory requests in any suitable manner. For the sake of
illustration, however, the description below assumes that
management module 15 receives inventory requests from other
elements of inventory system 10.
[0033] In response to receiving an inventory request, management
module 15 may select components or other elements of inventory
system 10 to complete the inventory request. For example, depending
on the type of operation requested, management module 15 may select
a particular mobile drive unit 20, inventory holder 30, inventory
station 50, storage space 90, and/or other suitable components and
elements of inventory system to facilitate completion of the
inventory request. After management module 15 selects suitable
components and/or elements to complete the inventory request,
management module 15 may then communicate information identifying
one or more of the selected components and/or elements to one or
more component of inventory system 10. This information may
identify the selected components or elements using some identifier,
such as a name or number associated with the selected components,
or using the location of the selected components.
[0034] For example, in retrieving inventory items 40 in a
particular embodiment of inventory system 10, management module 15
selects a mobile drive unit 20, inventory holder 30, and an
inventory station 50 to complete the operation. After selecting
these components, management module 15 may communicate information
identifying the selected inventory holder 30 and the selected
inventory station 50 to the selected mobile drive unit 20.
Management module 15 may identify inventory holder 30 to a selected
mobile drive unit 20 by specifying the selected inventory holder
30, by identifying a location for the selected inventory holder 30,
or in any other suitable manner. Management module 15 may also
transmit information specifying the selected inventory holder 30
and one or more inventory items 40 associated with the inventory
request to the selected inventory station 50 to identify inventory
items 40 to be selected in fulfilling the inventory request.
[0035] The selected components may then utilize the received
information to complete the inventory request in an appropriate
manner. For example, a selected mobile drive unit 20 may move a
selected inventory holder 30 to a selected inventory station 50 so
that an operator of the selected inventory station 50 may pick
requested inventory items 40 from the selected inventory holder 30
and pack them for shipment. FIGS. 2-4 illustrate further the
operation of a particular embodiment of inventory system 10 in
responding to particular types of inventory requests.
[0036] FIGS. 2 and 3 illustrate the operation of a particular
embodiment of inventory system 10 in responding to a particular
type of inventory request, referred to here as a "retrieval
request," which identifies one or more types of inventory items 40
to be retrieved from storage in inventory system 10. In the
embodiment of inventory system 10 illustrated by FIGS. 2 and 3,
inventory system 10 utilizes a two-step process to respond to
retrieval requests. More specifically, inventory system 10 first
retrieves a selected inventory holder 30 from a storage space 90
and moves the selected inventory holder 30 to a selected inventory
station 50. After the appropriate inventory items 40 have been
picked from inventory holder 30, inventory system 10 determines an
appropriate storage space 90 for the selected inventory holder 30
and moves inventory holder 30 to the storage space 90, moves the
inventory holder 30 in such a way as to present another face to
inventory station 50, or moves inventory holder 30 to another
inventory station 50. FIG. 2 illustrates operation of inventory
system 10 in selecting and retrieving inventory holder 30, while
FIG. 3 illustrates operation of inventory system 10 in storing the
selected inventory holder 30. Although the description below
describes inventory system 10 as performing a retrieval step and a
storage step when responding to retrieval requests, inventory
system 10 may, in a particular embodiment, be configured to perform
either of the retrieval step or the store step independently of the
other or to include any appropriate additional steps when
responding to retrieval requests.
[0037] FIG. 2, as noted above, illustrates operation of inventory
system 10 in retrieving an inventory holder 30 from storage within
workspace 70. FIG. 2 shows a top view of inventory system 10 that
includes mobile drive units 20, inventory holders 30, and inventory
stations 50. Furthermore, workspace 70 also includes multiple
storage spaces 90 which represent physical locations where
inventory holders 30 rest when not being used to respond to
inventory requests.
[0038] Additionally, in the illustrated embodiment, each inventory
station 50 has a queue associated with that inventory station 50
located adjacent to or near the inventory station 50. Each queue 80
provides space for one or more mobile drive units 20 and/or
inventory holders 30 to rest until the associated inventory station
50 is ready to process a request associated with that mobile drive
unit 20 or inventory holder 30. For example, a particular inventory
station 50 may be involved with processing several inventory
requests simultaneously, and several mobile drive units 20 may
arrive at that inventory station 50 at approximately the same time.
While the operator of that inventory station 50 processes inventory
items 40 of one inventory holder 30 based on an inventory request
associated with that inventory holder 30, mobile drive units 20
and/or inventory holders 30 associated with other inventory
requests may wait in queue 80 until the operator of the inventory
station 50 has finished processing the first inventory request.
[0039] In operation, management module 15 receives a retrieval
request that identifies one or more types of inventory items 40 to
be retrieved from storage in inventory system 10. Depending on the
configuration of inventory system 10, the retrieval request may
identify types of inventory items 40 to be retrieved, for example
by specifying a product name, or specific inventory items 40, for
example by identifying particular articles of luggage. In response
to receiving the retrieval request, management module 15 selects
one of inventory stations 50 at which the retrieval request will be
processed using suitable criteria. For the purposes of this
description, "processing" a retrieval request may include selecting
designated inventory items 40 from inventory holders 30 and placing
these inventory items 40 in a box for shipping, assembling a
finished product from the designated inventory items 40, counting
the number of the specified inventory items 40 in the inventory
holder 30, or processing the designated inventory items 40 in any
other appropriate manner based on the characteristics of inventory
system 10.
[0040] Management module 15 also selects one or more inventory
holders 30 that contain the identified inventory items 40 and one
or more mobile drive units 20 to move the selected inventory
holders 30 to the selected inventory station 50. Although the
description below focuses, for purposes of illustration, on an
embodiment of inventory system 10 that selects inventory station
50, inventory holder 30, and mobile drive unit 20 in a particular
order based on particular criteria, management module 15 may select
these components in any suitable order and may utilize any suitable
factors, criteria, or considerations in determining which
components to use as described in greater detail below.
Furthermore, management module 15 may select each component
independently or may base the selection of a particular component
on the selection of any other component.
[0041] As noted above, management module 15 may utilize any
suitable factors, criteria, or considerations in determining which
components of inventory system 10 to use in fulfilling the
retrieval request. The criteria utilized by management module 15 in
selecting an inventory station 50 may include, but is not limited
to, the distance between the selected inventory station 50 and
particular inventory holders 30 or mobile drive units 20, the work
history of the selected inventory station 50, the worker or station
capabilities at station 50, and the current contents of queue 80
associated with the selected inventory station 50. For example, in
a particular embodiment of inventory system 10, management module
15 calculates a score for each inventory station 50 with respect to
the requested inventory item 40. This score is a function of
several factors including a product density value, a drive unit
density value, a workload value, and a queue capacity value, as
described below. Management module 15 may then select an inventory
station 50 based on the score of the selected inventory station
50.
[0042] The product density value of a particular inventory station
50, in this example embodiment, measures the distribution of the
requested inventory item 40 relative to that inventory station 50.
As one example, management module 15 calculates the product density
value of the relevant inventory station 50 based on the distance
between the inventory station 50 and one or more inventory holders
30 currently storing inventory items 40 of the relevant item type.
More specifically, management module 15 calculates the product
density value based on both the number of inventory holders 30 near
inventory station 50 that hold the requested inventory item 40 and
on the inverse of the distance to these inventory holders 30. By
selecting an inventory station 50 that is close to several
inventory holders 30 with the requested inventory item 40,
management module 15 may be able to optimize operation of inventory
system 10.
[0043] In selecting a mobile drive unit 20 and/or inventory holder
30, management module 15 may also consider the fact that a
particular inventory holder 30 is already en route to the selected
inventory station 50 to fulfill another retrieval request, or that
the selected inventory station 50 is located on or near a path to
be traveled by a particular inventory holder 30 in fulfilling
another retrieval request. Thus, management module 15 may be able
to utilize mobile drive units 20 that are already in the process of
completing retrieval requests and, as a result, further optimize
use of system resources and/or minimize the amount of time taken to
fulfill the current retrieval request. Depending on the
configuration of inventory system 10, management module 15 may use
this information in any appropriate manner. For example, management
module 15 may set the product density value to some predetermined
maximum value if an inventory holder 30 storing an inventory item
40 of the relevant item type is already en route to that inventory
station 50 (or automatically choose the inventory holder).
[0044] The drive unit density value of a particular inventory
station 50, in this example embodiment, describes the distribution
of mobile drive units 20 relative to that inventory station 50.
Management module 15 may calculate the drive unit density value
based on the distance between the inventory station 50 and one or
more mobile drive units 20 available to respond to the retrieval
request. More specifically, management module 15 may calculate the
drive unit value based on both the number of available mobile drive
units 20 near inventory station 50 and the inverse of the distance
between each of these mobile drive units 20 and the inventory
station 50. By selecting an inventory station 50 that is close to
several free mobile drive units 20, management module 15 may be
able to further optimize operation of inventory system 10.
[0045] The workload value of a particular inventory station 50, in
the example embodiment, represents a measure of the work performed
by the current operator of that inventory station 50. For example,
management module 15 may calculate the workload value based on the
number of inventory requests fulfilled by the operator of that
inventory station 50 over a predetermined period of time, the
amount of time the operator has spent working on retrieval
requests, or any other appropriate measure of the work history of
the operator. Alternatively, the workload value may measure the
work history of that inventory station 50 for all operators. For
example, management module 15 may calculate the workload value
based on a number of inventory requests completed at that inventory
station 50 by any operator. By considering this workload value,
management module 15 may be capable of providing a more even
distribution of tasks between the various inventory stations 50
and/or operators active in inventory system 10.
[0046] The queue capacity value of a particular inventory station
50, in this example embodiment, describes the contents of queue 80
associated with that inventory station 50. Management module 15 may
determine the queue capacity value of a particular inventory
station 50 based on a number of open slots in queue 80 associated
with the inventory station 50, a number of inventory holders 30
currently waiting in queue 80, an anticipated wait time for
inventory holders 30 entering queue 80, or any other suitable
measure or value associated with the contents of queue 80. In the
example embodiment, management module 15 calculates a queue
capacity value for each inventory station 50 that is the inverse of
the number of open queue spots associated with that inventory
station 50. Management module 15 may be further configured to
prefer inventory stations 50 with a greater number of open queue
spaces, eliminate inventory stations 50 from consideration that
have no empty queue spaces, or use the information provided by the
queue capacity value in any appropriate manner. As a result,
management module 15 may be able to optimize operation of inventory
system 10 by limiting the amount of time mobile drive units 20 and
inventory holders 30 wait in queues 80.
[0047] As indicated above, management module 15 may then use the
relevant factors in any suitable manner to select the inventory
station 50, giving any appropriate weight or consideration to each
factor. In the example embodiment, management module 15 calculates
a score for each inventory station 50 based on a weighted sum of
the product density value, the mobile drive unit density value, the
workload value, and the queue capacity value with an appropriate
weight assigned to each value.
[0048] Management module 15 then selects the inventory station 50
with the lowest score to process the retrieval request. For the
purposes of this example, management module 15 is assumed to have
selected a particular inventory station 50, shown as selected
inventory station 50h in FIG. 2.
[0049] In addition to selecting an inventory station 50, management
module 15 selects an inventory holder 30 and a mobile drive unit 20
to facilitate completion of the retrieval request. As with
selecting inventory station 50, management module 15 may use any
appropriate criteria, factors, or considerations in selecting
inventory holder 30 and mobile drive unit 20. In selecting
inventory holder 30, the criteria utilized by management module 15
may include, but is not limited to, the distance between the
selected inventory holder 30 and one or more mobile drive units 20
or inventory stations 50, the contents of the selected inventory
holder 30, the relative placement of inventory items 40 in the
selected inventory holder 30, and the current commitments of the
selected inventory holder 30. In selecting mobile drive unit 20,
the criteria utilized by management module 15 may include, but is
not limited to, the distance between the selected mobile drive unit
20 and one or more inventory holders 30 or inventory stations 50
and the current availability of the selected mobile drive unit
20.
[0050] For example, in a particular embodiment, management module
15 selects inventory holder 30 by first determining which inventory
holders 30 currently store the requested inventory item 40.
Management module 15 may then select from the inventory holders 30
that are currently holding the requested inventory item 40 an
inventory holder 30 based on additional criteria. More
specifically, in a particular embodiment, management module 15
calculates a score for each inventory holder 30 that stores the
requested inventory item 40. This score is based, in part, on the
inverse of the distance from the inventory holder 30 to the
selected inventory station 50. In this embodiment, management
module 15 then selects the inventory holder 30 with the highest
score. For the purposes of example, management module 15 is assumed
to have selected a particular inventory holder 30, shown as
selected inventory holder 30x in FIG. 2.
[0051] Additionally, a particular embodiment of inventory system 10
may be configured to utilize retrieval requests identifying a
plurality of inventory items 40. In such an embodiment, management
module 15 may select an inventory holder 30 based on the number of
inventory items 40 identified by the retrieval request that are
currently stored in that inventory holder 30. For example,
management module 15 may select the inventory holder 30 holding the
greatest number of requested inventory items 40. Alternatively,
inventory holder 30 may identify a group of inventory holders 30
holding a minimum number of the requested inventory items 40 and
select a particular inventory holder 30 from that group based on
additional criteria.
[0052] Moreover, a particular embodiment of inventory system 10 may
also be configured to utilize retrieval requests identifying a
quantity of a particular inventory item 40 to be retrieved. In such
an embodiment, management module 15 may select an inventory holder
30 based on the number of units of the requested inventory item 40
stored on that inventory holder 30. For example, management module
15 may identify a group of inventory holders 30 currently holding a
quantity of the requested inventory item 40 that is greater than
the requested quantity of the inventory item 40 specified in the
retrieval request. Management module 15 may then select a
particular inventory holder 30 from this group based on additional
criteria.
[0053] Furthermore, inventory holders 30 may include a plurality of
faces, and each inventory item 40 stored in a particular inventory
holder 30 may be associated with one or more faces of that
inventory holder 30. Inventory items 40 may be accessible only from
one of the faces associated with the inventory item 40. For
example, inventory holder 30 may include four faces and a plurality
of inventory bins. Each inventory bin may be associated with one or
more particular faces. In particular, inventory bins located at a
corner of inventory holder 30 may be associated with both frame
faces forming the corner. In a particular embodiment, an inventory
bin may only be accessed through the one or more frame faces
associated with that inventory bin. Thus, when mobile drive unit 20
and inventory holder 30 arrive at inventory station 50, mobile
drive unit 20 may rotate inventory holder 30 to present a
particular face and allow an operator to select inventory items 40
from a particular inventory bin associated with that face. In such
an embodiment of inventory system 10, management module 15 may
consider the contents of faces of inventory holder 30 separately.
As a result, management module 15 may select inventory holders 30
based in part on the number of requested inventory items 40 or the
quantity of a single requested inventory item 40 stored on a single
face of inventory holder 30.
[0054] Management module 15 may also consider, when selecting an
inventory holder 30, whether a particular inventory holder 30 is
located in a storage space 90 appropriate for that inventory holder
30. For example, workspace 70 may be divided into a plurality of
storage regions with each storage region associated with inventory
holders 30 based on a particular characteristic of inventory
holders 30. In a particular embodiment, each inventory holder 30
may be assigned to a particular storage region based on how
frequently the inventory items 40 stored on that inventory holder
30 are requested in retrieval requests or other inventory requests.
Management module 15 may thus select an inventory holder 30 based
on whether the selected inventory holder 30 is located in a storage
region other than the storage region associated with that inventory
holder 30. In particular, management module 15 may give preference
to inventory holders 30 that are currently stored in the wrong
storage region. As a result, particular embodiments of inventory
system 10 may assign frequently requested inventory holders 30
storage spaces 90 closer to inventory stations 50 and may utilize
retrieval requests to tune the distribution of inventory holders 30
by correcting incorrectly located inventory holders 30.
[0055] Particular embodiments of inventory system 10 may tune the
location of inventory holders 30 in various manners. As one
example, in particular embodiments of inventory system 10,
management module 15 determines a tuning range for each a plurality
of storage regions. The tuning range of a particular storage region
describes the inventory holders 30 that are appropriate for storage
in that storage region. The tuning region describes these inventory
holders 30 by specifying a range of values appropriate for a
particular characteristic of these inventory holders 30, referred
to here as a "tuning value." For example, management module 15 may
calculate a holder velocity for each inventory holder 30 based on
how often that inventory holder 30 is selected to respond to
retrieval requests and may use this holder velocity as a tuning
value for tuning the location of inventory holders 30 in inventory
system 10.
[0056] In such embodiments, management module 15 may tune the
location of inventory holders 30 by identifying a first group of
inventory holders 30 that includes some or all inventory holders 30
that currently store the requested inventory items. Management
module 15 then determines a tuning differential for each inventory
holder 30 in this group. The tuning differential of a particular
inventory holder 30 represents a numeric measure of how far the
holder velocity of that inventory holder 30 is outside the tuning
range of the tuning region in which that inventory holder 30 is
located. Management module 15 may then identify a second group of
inventory holders 30 that have a tuning differential greater than
some predetermined threshold. Management module 15 may then select,
based on appropriate considerations, an inventory holder 30 from
that second group. As a result, management module 15 may be able to
bias the selection of inventory holders 30 towards inventory
holders 30 that are, with respect to the relevant tuning value,
badly misplaced in inventory system 10.
[0057] Overuse of tuning may, however, reduce the overall
efficiency of inventory system 10. As a result, in particular
embodiments of inventory system 10, management module 15 may use
certain techniques to limit the effects of tuning on overall
efficiency. In particular embodiments, management module 15 may be
configured to tune the location of inventory holders 30 based on a
tuning frequency. For example, management module 15 may be
configured to tune the location when responding to every 100th
retrieval request. As a result, every 100th retrieval request,
management module 15 may consider the tuning of inventory holders
30, as described above, when selecting an inventory holder 30 to
fulfill the retrieval request. For all other retrieval requests,
management module 15 may select inventory holder 30 without regard
for the tuning of the selected inventory holder 30. Thus, by
properly configuring the tuning frequency utilized by management
module 15, an operator of inventory system 10 can maximize
efficient fulfillment of retrieval requests.
[0058] After selecting inventory station 50 and inventory holder
30, management module 15 selects a mobile drive to move the
selected inventory holder 30 to the selected inventory station 50.
In selecting mobile drive unit 20, management module 15 may, in a
particular embodiment, determine which mobile drive units 20 are
available to retrieve the selected inventory holder 30. To
determine which mobile drive units 20 are available, management
module 15 may utilize information previously stored on management
module 15, or information received by management module 15 from
mobile drive units 20 or other components of inventory system 10.
For example, in a particular embodiment, management module 15
stores information indicating which mobile drive unit 20 are
currently fulfilling inventory requests in inventory system 10.
Management module 15 may then use this information to select an
appropriate mobile drive unit 20 for the current retrieval request.
As another example, management module 15 may poll one or more
mobile drive units 20 to determine whether each of these mobile
drive units 20 is available before selecting the mobile drive unit
20 to fulfill the current retrieval request. In general, mobile
drive unit 20 may use any appropriate method, based on the
configuration and characteristics of inventory system 10, to
determine which mobile drive unit 20 are available.
[0059] After determining which mobile drive units 20 are available,
management module 15 selects a particular mobile drive unit 20 from
the available mobile drive units 20 to fulfill the retrieval
request. Management module 15 may utilize any additional criteria
to determine which of the available mobile drive units 20 to use.
For example, in particular embodiment, management module 15
calculates a score for each available mobile drive unit 20. This
score is based, in part, on the distance from that particular
mobile drive unit 20 to the selected inventory station 50 or the
selected inventory holder 30. In this embodiment, management module
15 then selects the mobile drive unit 20 with the best score. For
the purposes of this example, management module 15 is assumed to
have selected a particular mobile drive unit 20, shown as selected
mobile drive unit 20x in FIG. 2
[0060] After selecting appropriate components of inventory system
10, management module 15 generates or retrieves information,
referred to here as a "retrieval command", that identifies the
selected inventory holder 30 or the location of the selected
inventory holder 30 and the selected inventory station 50 or the
location of the selected inventory station 50. Management module 15
then transmits this retrieval command to the selected mobile drive
unit 20. Management module 15 may also transmit the retrieval
command or other information to the selected inventory station 50
to be used by the operator of the selected inventory station 50 in
completing the retrieval request.
[0061] After receiving the retrieval command, selected mobile drive
unit 20x moves to selected inventory holder 30x, as shown by arrow
210 in FIG. 2, based on a location or other information specified
in the retrieval command. Selected mobile drive unit 20x then
couples to selected inventory holder 30x. After coupling to
selected inventory holder 30x, selected mobile drive unit 20x moves
to selected inventory station 50h as shown by arrow 220 in FIG. 2.
As indicated by FIG. 2, selected mobile drive unit 20x may move
selected inventory holder 30x through one or more spaces in a
particular queue 80, queue 80h, that is associated with selected
inventory station 50h. Moreover, selected mobile drive unit 20 may
pause one or more times while moving through queue 80h so that
selected mobile drive unit 20 arrives at inventory station 50 at an
appropriate time. For example, selected mobile drive unit 20 may
pause one or more times in queue 80h while inventory holders 30
associated with other inventory requests are processed at selected
inventory station 50h.
[0062] Once selected mobile drive unit 20x has brought selected
inventory holder 30x to the selected inventory station 50h, an
operator associated with selected inventory station 50h may begin
removing requested inventory items 40 from selected inventory
holder 30x, counting the requested inventory items 40 in selected
inventory holder 30x, or performing any other appropriate
processing task associated with the retrieval request.
Additionally, in a particular embodiment, selected inventory
station 50h and/or selected mobile drive unit 20x may notify
management module 15 once the retrieval request has been completed
to indicate that selected inventory station 50h is available for
subsequent retrieval requests or that selected mobile drive unit
20x is ready to store selected inventory holder 30x.
[0063] Thus, with the appropriate choice of selection criteria,
particular embodiments of inventory station 10 can be configured to
execute retrieval requests quickly, thereby increasing the
throughput of inventory system 10. Additionally, by selecting
components to execute retrieval requests based on the work history
of those components, particular embodiments may also provide more
evenly distributed workloads for components of inventory system 10
and/or human operators. Moreover, particular embodiments of
inventory system 10 may be capable, in executing a particular
retrieval request, of leveraging operations being executed for
other inventory requests, thereby providing even greater
operational benefits. As a result, inventory system 10 may provide
a fast and efficient system for retrieving inventory items 40 from
storage.
[0064] FIG. 3, as noted above, illustrates operation of inventory
system 10 in moving inventory holders 30 to storage spaces 90
within workspace 70 of inventory system 10. Management module 15
may decide to initiate the storage operation based on an inventory
request received from an operator of inventory system 10, based on
communication with another component of inventory station 50, or
based on any suitable event occurring in inventory system 10 or any
appropriate information available within inventory system 10. For
the purposes of illustration, however, the description below
focuses on an embodiment of inventory system 10 in which management
module 15 initiates a storage operation in response to information
received from mobile drive unit 20 indicating that mobile drive
unit 20 is coupled to an inventory holder 30 that is ready for
storage.
[0065] After receiving information indicating that inventory holder
30 is ready for storage, management module 15 initiates the storage
operation. As part of the storage operation, management module 15
may select a storage space 90 based on a classification of the
inventory holder 30 to be stored and a classification of a storage
space 90 selected by management module 15. The classifications used
by management module 15 in selecting the storage space 90 may
represent any suitable classification of inventory holder 30 and
any suitable classification of storage space 90.
[0066] For example, management module 15 may utilize a holder
velocity as the relevant classification of inventory holder 30. The
holder velocity of an inventory holder 30 represents a measure of
the frequency with which inventory items 40 stored on that
inventory holder 30 are requested in inventory requests. In such an
embodiment, management module 15 may also use a range of holder
velocities associated with each storage space 90 as the relevant
classification for storage spaces 90. Thus, management module 15
may select a storage space 90 for a particular inventory holder 30
by matching the holder velocity of the inventory holder 30 to be
stored with the range of holder velocities associated with one or
more available storage spaces.
[0067] In a particular embodiment, management module 15 calculates
the holder velocity based on an item velocity of one or more
inventory items 40 stored on that inventory holder 30. The item
velocities represent, in any appropriate form, the frequency with
which the relevant inventory item 40 is requested during operation
of inventory system 10. In general, management module 15 may
calculate the holder velocity of a particular inventory holder 30
in any appropriate manner from the inventory velocities of
inventory items 40 stored on that inventory holder 30. As one
example, management module 15 may calculate the holder velocity for
a particular inventory holder 30 by averaging the item velocities
of all the inventory items 40 stored on that inventory holder
30.
[0068] As another example, management module 15 may determine a
weight for each inventory item 40 based on the number of units of
that inventory item 40 stored on the relevant inventory holder 30.
Management module 15 may also calculate a weighted frequency for
each inventory item 40 by multiplying the item velocity for each
inventory item 40 by the weight calculated for that inventory item
40. Management module 15 may then calculate the holder velocity for
that inventory holder 30 by averaging the weighted frequencies of
all the inventory items 40 stored on inventory holder 30.
[0069] Management module 15 then selects a storage space 90 based
on the classification of the inventory holder 30 to be stored and
the classification of the selected storage space 90. For example,
in a particular embodiment, management module 15 utilizes holder
velocities as the relevant classification for inventory holders 30,
and a range of holder velocities associated with each storage space
90 as the relevant classification for storage spaces 90. Thus,
management module 15 selects a particular storage space 90 for an
inventory holder 30 to be stored on identifying a particular
storage space 90 associated with a holder velocity range that
includes the holder velocity of the inventory holder 30 to be
stored.
[0070] To facilitate the selection of storage spaces 90 during
storage operations, management module 15, at any appropriate time,
may also define, calculate, or otherwise identify a plurality of
storage regions 100 that group storage spaces 90 based on one or
more characteristics of the grouped storage spaces 90. For example,
management module 15 may group storage spaces 90 into storage
regions 100 based on a distance between each storage space 90 and
one or more inventory stations 50. Each storage region 100 may then
be associated with a storage space classification that management
module 15 uses in selecting an appropriate storage space 90, as
described above. For example, management module 15 may associate a
range of holder velocities with each of these storage regions
100.
[0071] In the illustrated embodiment, management module 15 divides
storage spaces 90 into storage regions 100a-d based on a distance
between each storage space 90 and a group of one or more inventory
stations 50. For example, management module 15 may assign each
storage space 90 to a particular storage region 100 based on one or
more distances between that storage space 90 and any one or more
inventory stations 50 in inventory system 10. Management module 15
may assign each storage space 90 based on a maximum distance, a
minimum distance, an average distance or any other one or more
distances between that storage space 90 and inventory stations 50
of inventory system 10.
[0072] Alternatively, management module 15 may identify a group of
inventory stations 50 based on a station criteria. The station
criteria defines a particular characteristic, property,
consideration, and/or criteria for inventory stations 50 to be
included in the group. The station criteria may pertain to the
active status of inventory stations 50 in the group, the type of
inventory requests that the inventory stations 50 are configured to
process, or any other appropriate characteristic of inventory
stations 50. Thus, management module 15 may identify the group of
all currently active inventory stations 50, all inventory stations
50 currently configured to process retrieval and/or replenishment
requests, or any other group of inventory stations 50 depending on
the station criteria used. After identifying the inventory stations
50 in the group, management module 15 may divide storage spaces 90
into storage regions 100 based on one or more distances between
each storage space 90 and the inventory stations 50 in the
group.
[0073] Additionally, management module 15 may update the group of
inventory stations 50 and reassign storage spaces 90 to storage
regions 100 based on one or more distances between each storage
space 90 and inventory stations 50 in the updated group. For
example, management module 15 may detect that an additional
inventory station 50 has become active. In response to detecting
the new inventory station 50, management module 15 may identify an
updated group of inventory stations 50 based on the station
criteria. Management module 15 may then reassign storage spaces 90
to storage regions 100 based on a maximum distance, a minimum
distance, an average distance, or any other one or more distances
between each storage space and the inventory stations 50 in the
updated group.
[0074] After grouping storage spaces 90 into storage regions 100
based on the appropriate characteristic of storage spaces 90, such
as a distance to one or more inventory station 50, management
module 15 may select a storage region 100 for the inventory holder
30 to be stored based on a classification of that inventory holder
30 and a classification associated with the selected storage region
100 and/or the storage spaces 90 within that storage region 100.
For example, management module 15 may select a storage region 100
based on the holder velocity of a particular inventory holder 30
and a range of holder velocities associated with the selected
storage region 100. Management module 15 may then select a
particular storage space 90 within that storage region 100 based on
any additional criteria. For example, management module 15 may
select a particular storage space 90 within the selected storage
region 100 based on a distance between the selected storage space
90 and the inventory holder 30 to be stored.
[0075] In the illustrated embodiment, management module 15, at an
appropriate time, defines storage regions 100 by grouping storage
spaces 90 based on the average distance between each storage space
90 and all inventory stations 50 in inventory system 10. Management
module 15 also associates a range of holder velocities with each
storage region 100. For the sake of illustration, it is assumed
that storage region 100a is associated with a range of holder
velocities greater than 0.3, that storage region 100b is associated
with holder velocities between 0.3 and 0.2, that storage region
100c is associated with holder velocities between 0.2 and 0.1, and
that storage region 100d is associated with holder velocities less
than 0.1. Then after initiating a storage operation, management
module 15 selects a storage region 90 for inventory holder 30x. For
the sake of illustration, it is assumed that inventory holder 30x
has a holder velocity of 0.15. Thus, in the illustrated embodiment,
management module 15 selects a particular storage region 100
associated with a range of holder velocities that includes the
holder velocity, 0.15, of inventory holder 30x or, in this case,
storage region 100c. After selecting storage region 100c,
management module 15 then selects a storage location 90 from among
the available storage locations 90 in storage region 100c, storage
locations 90a-c. In particular, management module 15 selects from
storage spaces 90a-c the storage space 90 closest to inventory
holder 30x. As illustrated in FIG. 3, the closest storage space
90a-c is storage space 90c.
[0076] By selecting a storage space 90 for a particular inventory
holder 30 based, in part, on the holder velocity of that inventory
holder 30, management module 15 may be able to select remote or
otherwise undesirable storage spaces 90 for inventory holders 30
with lower holder velocities and select easily accessible or
otherwise desirable storage spaces 90 for inventory holders 30 with
higher holder velocities. This may reduce the time needed to move
the most frequently requested inventory items 40 to inventory
stations 50 for processing, thereby reducing the amount of time
taken to fulfill certain types of inventory requests.
[0077] After selecting a storage space 90, management module 15
transmits information identifying the selected storage space 90 to
the appropriate mobile drive unit 20. Upon receiving this
information, the relevant mobile drive unit 20 moves the inventory
holder 30 to the selected storage space 90, as indicated in FIG. 3
by arrow 310. Mobile drive unit 20 may then undock from the
inventory holder 30 after arriving at the selected storage space
90. Mobile drive unit 20 may then move away from the selected
storage space 90, leaving the inventory holder 30 in the selected
storage space 90, and begin responding to other inventory requests.
In the illustrated embodiment, this is shown by arrow 320.
[0078] Additionally, in a particular embodiment of inventory system
10, management module 15 may store information related to the
availability of each storage space 90. In such an embodiment,
mobile drive unit 20 may notify management module 15 that the
selected storage space 90 is now full. Management module 15 may
alternatively determine that the selected storage space 90 is no
longer available using other techniques depending on the
configuration of inventory system 10. As a result, management
module 15 may independently generate and store information
indicating that the selected storage space 90 is now full.
Management module 15 may then use this information in selecting
storage spaces 90 for subsequent storage operations or in
fulfilling other types of inventory requests. Furthermore,
management module 15 may store information identifying the location
of inventory holders 30 and/or inventory items 40 in inventory
system 10 and, thus, may store information describing the new
location and/or the contents of the stored inventory holder 30.
[0079] Consequently, particular embodiments of inventory system 10
may provide an optimized method for selecting storage spaces 90 for
inventory holders 30. This may improve the ability of inventory
system 10 to respond to subsequent retrieval and replenishment
requests efficiently. As a result, the store procedure utilized by
particular embodiments of inventory system 10 may provide
significant operational benefits.
[0080] FIG. 4 illustrates operation of inventory system 10 in
replenishing an inventory holder 30 within workspace 70. During
execution of a replenishment operation, mobile drive unit 20 moves
inventory holder 30 from a storage space 90 to inventory station 50
to be filled with inventory items 40. By selecting inventory holder
30 for the inventory item 40 to be stored based on a classification
of the inventory item 40 to be stored and a classification of one
or more inventory items 40 already on the selected inventory holder
30, particular embodiments of inventory system 10 may group and
store inventory items 40 in a manner that results in more efficient
operation of inventory system 10.
[0081] Management module 15 decides at an appropriate time to
initiate a replenishment operation. Management module 15 may decide
to initiate the replenishment operation based on a predetermined
replenishment schedule or in response to receiving a particular
type of inventory request, referred to here as "a replenishment
request", that identifies an inventory item 40 to be added to
inventory system 10. For example, inventory system 10 may be
configured to replenish inventory holders 30 every evening and
management module 15 may initiate a replenishment operation for
appropriate inventory holders 30 on a daily basis. Alternatively,
management module 15 may receive information from an inventory
station 50 or another component indicating that inventory system 10
has received a delivery of inventory items 40 that are ready to be
stored in inventory holders 30. In the illustrated embodiment,
inventory station 50z is assumed to have transmitted a
replenishment request to management module 15 in response to
receiving a pallet of inventory items 40z to be stored.
[0082] In executing a replenishment operation, management module 15
selects an inventory holder 30 and a mobile drive unit 20.
Additionally, in certain circumstances, management module 15 may
also select an inventory station 50 at which to complete the
replenishment operation. Management module 15 may choose inventory
holder 30, mobile drive unit 20 and, if appropriate, inventory
station 50 in any appropriate order. Additionally, management
module 15 may use any suitable factors, criteria, or considerations
in choosing the selected inventory holder 30, mobile drive unit 20,
and inventory station 50.
[0083] In a particular embodiment, management module 15 selects
inventory holder 30 based on a classification of the inventory item
40 to be stored and a classification of one or more inventory items
40 already on the selected inventory holder 30. For example, in a
particular embodiment, management module 15 groups more frequently
requested inventory items 40 on particular inventory holders 30 and
less frequently requested inventory items 40 on other inventory
holders 30 and then stores the more frequently requested inventory
items 40 in storage spaces 90 that are closer to inventory stations
50. As a result, management module 15 may be able to reduce the
time required to complete retrieval operations and other tasks
executed by inventory system 10 by keeping frequently-requested
inventory items 40 close to inventory stations 50.
[0084] In such an embodiment, management module 15 calculates an
item velocity for each inventory item 40 stored on inventory system
10. The item velocity may represent any suitable value determined
based in any manner on a frequency with which that inventory item
40 is requested during operation of inventory system 10.
[0085] For the purposes of this description and the claims that
follow, an inventory item 40 is considered to be "requested"
whenever that inventory item 40 is involved in an activity
undertaken within inventory system 10 or any designated subset of
the activities undertaken within inventory system 10. A particular
inventory item 40 may be requested as a result of management module
15 receiving any inventory request that identifies the inventory
item 40 or, alternatively, a particular type of inventory request,
such as a retrieval request, that identifies the inventory item 40
in question. As one example, inventory system 10 may represent a
mail-order warehouse, and management module 15 may determine item
velocities for each inventory item 40 based in some manner on the
frequency with which that inventory item 40 is retrieved to fulfill
merchandise orders received by the warehouse. As another example,
inventory system 10 may represent a facility for processing
returned merchandise, and management module 15 may calculate the
item velocities for each inventory item 40 based on the frequency
with which that inventory item 40 is returned by customers. In
general, the item velocity may represent any suitable calculation
or measure based, in any appropriate manner, on the frequency with
which the relevant inventory item 40 is requested for any one or
more operations performed by inventory system 10.
[0086] Additionally, the item velocity may reflect the frequency
with which the inventory item 40 is requested over a predetermined
absolute time period, over an amount of time defined with respect
to particular events, or within any other suitable measurement of
time. As one example, the item velocity may reflect the average
number of requests for a particular inventory item 40 that are
received in a single day. As another example the item velocity may
reflect the number of times that inventory item 40 is requested in
a given number of inventory requests. As a further example, the
item velocity may be manually set by a warehouse manager in
anticipation of an inventory item becoming popular or
unpopular.
[0087] After determining item velocities for appropriate inventory
items 40, management module 15 may select an inventory holder 30
based in some appropriate manner on the item velocity of the
inventory item 40 to be stored and the item velocity of one or more
inventory items 40 on each inventory holder 30. For example, in a
particular embodiment, management module 15 calculates a holder
velocity for each inventory holder 30 in inventory system 10, the
holder velocity representing the average item velocity of inventory
items 40 stored on that inventory holder 30. Management module 15
may then select the inventory holder 30 based on a velocity
difference of the inventory holder 30, the velocity difference
representing the difference between the item velocity of the
inventory item 40 to be stored and the holder velocity of the
selected inventory holder 30.
[0088] By minimizing the velocity difference in selecting inventory
holders 30, management module 15 may be able to group inventory
items 40 in inventory holders 30 based on item velocities of the
stored inventory items 40. Inventory system 10 may then store the
selected inventory holder 30 based on the holder velocity of the
selected inventory holder 30. As a result, management module 15 may
be able to group and store less frequently requested inventory
items 40 far from inventory stations 50 and more frequently
requested inventory items 40 close to inventory stations 50.
[0089] Additionally, in particular embodiments, management module
15 may be configured to create diversely-stocked inventory holders
30. Because grouping inventory items 40 based solely on item
velocity may produce inventory holders 30 that contain only a
single or a small number of different inventory items 40,
management module 15 may consider the marginal benefit of storing
the inventory item 40 in a particular inventory holder 30 before
selecting that inventory holder 30. More specifically, management
module 15 may, when selecting inventory holder 30, consider an
increase in the likelihood that one or more inventory items 40
stored on that inventory holder 30 would be requested in an
inventory request received by management module 15.
[0090] In such an embodiment, management module 15 may calculate,
for inventory holders 30, one or more pick number probabilities
associated with one or more pick numbers. Each pick number
probability represents a likelihood that a single inventory request
will request a number of inventory items 40 stored on inventory
holder 30 that is equal to the pick number. For example, for a pick
number probability of three, management module 15 calculates the
likelihood that a single inventory request will request three
inventory items 40 that are stored on inventory holder 30. In a
particular embodiment, management module 15 is configured to
calculate a pick number probability for pick numbers of one, two,
and three. These pick numbers represent, respectively, the
likelihood that a single inventory request received by management
module 15 will identify one, two, and three inventory items 40
stored on inventory holder 30. Furthermore, management module 15
may calculate these pick number probabilities for the relevant
inventory holders 30 based on the inventory items 40 currently
stored on those inventory holder 30. Management module 15 may then
re-calculate these pick number probabilities for each of the
relevant inventory holders 30 assuming the inventory item 40 to be
stored is added to that inventory holder 30 and may update the pick
number probabilities as appropriate.
[0091] Management module 15 may then calculate a usefulness value
for each inventory holder 30 representing the sum of the pick
probabilities calculated for that inventory holder 30. More
specifically, management module 15 may calculate a first usefulness
value based on the inventory items 40 currently stored on the
inventory holder 30 and a second usefulness value based on the
contents of inventory holder 30 if the inventory item 40 to be
stored were added to that inventory holder 30. Management module 15
may then determine a usefulness differential for each inventory
holder 30 based on a change in the usefulness value that would
result if the inventory item 40 to be stored were added to the
inventory holder 30. Management module 15 may then select inventory
holder 30 based, in part, on this usefulness differential. Because
the usefulness differential will be greater for inventory holders
30 that do not already hold the inventory item 40 in question,
inventory system 10 may, as a result of these replenishment
techniques, create inventory holders 30 that hold a diverse
collection of inventory items 40.
[0092] Management module 15 may then select an inventory holder 30
on which to store inventory item 40 based, in any appropriate
manner, on the item velocity of the inventory item 40 to be stored
and the holder velocity and usefulness differential of the selected
inventory holder 30. For example, in a particular embodiment,
management module 15 calculates a velocity similarity for each
inventory holder 30, equal to one minus the absolute value of the
difference between the item velocity of inventory item 40 and the
holder velocity of that inventory holder 30. Management module 15
then also calculates a score for each inventory holder 30 based on
the product of the velocity similarity and the usefulness
differential. By selecting inventory holder 30 based on these
values, management module 15 may be able produce inventory holders
30 that contain a diverse selection of inventory items 40 with
similar item velocities. In the illustrated embodiment, management
module 15 is assumed to have selected inventory holder 30z on which
to store inventory items 40z.
[0093] After selecting inventory holder 30, management module 15
may then select a particular mobile drive unit 20 to transport that
inventory holder 30 and, if appropriate, a particular inventory
station 50 to complete the replenishment operation. Management
module 15 may use any appropriate criteria, factors, or
considerations in selecting mobile drive unit 20 and inventory
station 50. For example, in a particular embodiment, an inventory
station 50 receives a pallet of inventory items 40 to be stored in
inventory system 10 and transmits a replenishment request to
management module 15 specifying the inventory items 40 to be
stored. In such an embodiment, management module 15 may select only
an appropriate inventory holder 30 on which to store the inventory
item 40 and, from a pool of currently available mobile drive units
20, the mobile drive unit 20 closest to the selected inventory
holder 30 to transport the selected inventory holder 30 to the
inventory station 50 that transmitted the replenishment request. As
indicated above, in the illustrated embodiment, inventory station
50z is assumed to have transmitted the replenishment request to
management module 15 in response to receiving a pallet of inventory
items 40z to be stored.
[0094] In alternative embodiments, management module 15 may
generate the replenishment request itself and subsequently selects
the inventory station 50 from a group of inventory stations 50 that
may include, depending on the configuration of inventory system 10,
all inventory stations 50 in inventory system 10 or all currently
active inventory stations 50. Moreover, inventory system 10 may
have reconfigurable inventory stations 50 that may, at any
particular time, be designated to process only one of many
different types of inventory requests. For example, each inventory
station 50 may, at a given time, be configured to handle only
retrieval requests or only replenishment requests. In such an
embodiment, management module 15 may select the inventory station
50 from a group of inventory stations 50 that includes all active
inventory stations 50 that are currently configured to process
replenishment requests.
[0095] After management module 15 has selected an appropriate
inventory holder 30, mobile drive unit 20 and inventory station 50,
management module 15 may then transmit information identifying the
selected inventory holder 30 and the selected inventory station 50
to the selected mobile drive units 20. Alternatively, management
module 15 may transmit information identifying a location of the
selected inventory holder 30 and/or a location of the selected
inventory station 50 to the selected mobile drive unit 20.
Management module 15 may also transmit additional information
pertaining to the replenishment request to the selected inventory
station 50, such as a number of units of the inventory item 40 to
store in the selected inventory holder 30, a particular bin on the
selected inventory holder 30 in which to place the inventory item
40, or any other appropriate information to be used in processing
the replenishment request.
[0096] The selected mobile drive units 20 then moves to the
selected inventory holder 30 and couples to the selected inventory
holder 30. This is illustrated in FIG. 4 by arrow 410. After
coupling to the inventory holder 30, the selected mobile drive unit
20 then moves the selected inventory holder 30 to the selected
inventory station 50. This is illustrated in FIG. 4 by arrow
420.
[0097] Once the selected inventory holder 30 arrives at the
selected inventory station 50, an operator at the selected
inventory station 50 may process the replenishment request in any
appropriate manner. In a particular embodiment, the operator stores
a predetermined number of units of the inventory item 40 to be
stored in the selected inventory holder 30. Inventory station 50 or
the operator of inventory station 50 may then transmit information
to management module 15 or other components of inventory system 10
indicating that the replenishment request has been completed.
Inventory system 10 may then execute a storage operation using, for
example, the techniques described above to return the selected
inventory holder 30 to a storage space 90 in workspace 70.
[0098] Although the above description focuses on an embodiment of
inventory system 10 that utilize a single mobile drive unit 20,
inventory holder 30, and inventory station 50 in completing the
replenishment operation, inventory system 10 may utilize any
appropriate number of inventory holders 30, mobile drive units 20,
and inventory stations 50 to complete the replenishment operation.
For example, the replenishment request may identify multiple
inventory items 40 to be stored and management module 15 may select
one or more inventory holders 30 in which to store these inventory
items 40 and one or more mobile drive units 20 to transport the
selected inventory holders 30.
[0099] Additionally, in particular embodiments, management module
15 may, during replenishment operations, distribute the storage of
a single inventory item 40 over multiple inventory holders 30.
Management module 15 may store the inventory item 40 in multiple
inventory holders 30 to spread the inventory item 40 among many
inventory holder 30 and thereby allow inventory system 10 to store
that inventory item 40 in several places in workspace 70. More
specifically, management module 15 may allocate a portion of a
replenishment quantity specified by the replenishment request to a
first selected inventory holder 30. Management module 15 may then
select additional inventory holders 30 and allocate additional
portions of the replenishment quantity to the additional inventory
holders 30 until all of the remaining replenishment quantity has
been allocated to a particular inventory holder 30.
[0100] Management module 15 may also use multiple inventory holders
30 to store the inventory item 40 when management module 15
determines that a first selected inventory holder 30 does not
possess enough unused storage capacity to store all the units of
the inventory item 40 specified by the replenishment request. More
specifically, management module 15 may determine that the
replenishment quantity exceeds an unused storage capacity of the
first selected inventory holder 30. The unused storage capacity may
represent all the unused storage capacity of the selected inventory
holder 30, unused capacity in currently empty bins of the selected
inventory holder 30, unused capacity in bins of the selected
inventory holder 30 that are already storing the inventory item 40,
or any other suitable measure of unused storage capacity. As a
result of determining that the replenishment quantity exceeds the
unused storage capacity of the first selected inventory holder 30,
management module 15 may select additional inventory holders 30 as
needed until the unused storage capacity of all the selected
inventory holders 30 is equal to or greater than the replenishment
quantity.
[0101] Furthermore, although the above description focuses on an
embodiment of inventory system 10 that selects an inventory holder
30 based on item velocities and/or product diversity
considerations, management module 15 may select inventory holder 30
based on any appropriate classification of the relevant inventory
items 40. For example, management module 15 may select inventory
holder 30 based on expiration dates of the relevant inventory items
40; restocking schedules; a season or event associated with the
relevant inventory items 40, such as Halloween or Easter; a common
theme associated with the relevant inventory items 40, such as
baseball equipment or cooking utensils; synergy between inventory
items such that they are commonly ordered together; and/or any
other appropriate classification of the relevant inventory items
40. By grouping inventory items 40 on inventory holders 30 based on
one or more classifications of the relevant inventory items 40,
particular embodiments of inventory system 10 may distribute
inventory items 40 among inventory holders 30 in a manner that
allows for more intelligent storage of inventory holders 30.
[0102] Additionally, by creating inventory holders 30 that offer a
diverse selection of inventory items 40, management module 15 may
increase the likelihood that a selected inventory holder 30 will be
able to provide multiple inventory items 40 requested by any given
inventory request. This may further reduce the amount of time
needed to fulfill subsequent inventory requests. Thus, the
described replenishment techniques may increase operational
efficiency of particular embodiments of inventory system 10.
[0103] FIG. 5 is a flowchart illustrating example functionality of
a particular embodiment of management module 15 in executing a
retrieval operation. In the described embodiment, the process
begins at step 500 with management module 15 receiving a retrieval
request that identifies an inventory item 40. After receiving the
retrieval request, management module 15 selects an inventory
station 50 at which the retrieval request will be fulfilled. As
noted above, management module 15 may utilize any appropriate
criteria, factors, or considerations in selecting an appropriate
inventory station 50. In the illustrated embodiment, management
module 15 calculates a score for each available inventory station
50 and selects an inventory station 50 based on its score. These
calculations may be performed when management module 15.
Alternatively, management module 15 may perform the calculation at
other appropriate times and store the results for later use in
responding to a retrieval request.
[0104] In calculating the scores for inventory stations 50,
management module 15 calculates, at step 510, a time-to-fill value
for each inventory station based on a distribution of the inventory
item 40 relative to each inventory station 50. Management module 15
also calculates a drive-unit density value for each inventory
station 50, at step 520, based on a distribution of available
mobile drive units 20 relative to each inventory station 50.
Additionally, management module 15 calculates a workload value for
each inventory station 50, at step 530, based on an amount of work
that has been performed at that inventory station 50 over a
predetermined time period. Management module 15 also calculates a
queue capacity value for each inventory station 50, at step 540,
based on contents of a queue associated with that inventory station
50. At step 550, management module 15 then sums the time-to-fill
value, the drive-unit density value, the workload value, and the
queue capacity value for each inventory station 50 to produce a
score for that inventory station 50. Management module 15 selects
the inventory station 50 with the best score at step 560. More
specifically, in the described embodiment, management module 15
selects the inventory station 50 with the highest score.
[0105] After selecting an inventory station 50, management module
15 selects an inventory holder 30 that stores the requested
inventory item 40 at step 570. As noted above, management module 15
may select the inventory holder 30 based on any appropriate
factors, criteria, or considerations. Examples of such factors may
include, but are not limited to, the contents of inventory holders
30, their location relative to inventory stations 50 or mobile
drive units 20, existing assignments of inventory holders 30,
tuning considerations, and/or any other appropriate factors.
[0106] At step 580, management module 15 selects a mobile drive
unit 20 to move the selected inventory holder 30 to the selected
inventory station 50. As noted above, management module 15 may also
select the mobile drive unit 20 based any appropriate factors,
criteria, or considerations. Examples of such factors may include,
but are not limited to, the location of mobile drive units 20
relative to the selected inventory station 50 or the selected
inventory holder 30. .After selecting an inventory station 50, an
inventory holder 30, and a mobile drive unit 20, management module
15 transmits information identifying the selected inventory station
50 and the selected inventory holder 30 to the selected mobile
drive unit 20 at step 590.
[0107] After management module 15 has transmitted this information
to the selected mobile drive unit 20, appropriate elements of
inventory system 10 may perform appropriate actions to complete the
retrieval operation. For, in particular embodiments, the selected
mobile drive unit 20 moves to the selected inventory holder 30. The
selected mobile drive unit 20 then couples to the selected
inventory holder. The selected mobile drive unit 20 then moves the
selected inventory holder 30 to the selected inventory station 50.
An agent or operator located at the selected inventory station 50
may then select the requested inventory item 40 from the selected
inventory holder 30 and placing the inventory item 40 in a box to
be shipped to a customer and/or take any other suitable actions to
complete the retrieval operation.
[0108] FIG. 6 is a flowchart illustrating example functionality of
a particular embodiment of management module 15 in executing a
storage operation. The process begins at step 600 with management
module 15 detecting that an inventory holder 30 is available for
storage. As described above, storage operations may be executed at
any appropriate time, including at the completion of a retrieval
request. Thus, management module 15 may detect that an inventory
holder 30 is available for storage by determining that a previously
received retrieval request has been completed by suitable
components of inventory system 10 and that one or more inventory
holders 30 involved in the fulfillment of the retrieval request are
now available to be stored.
[0109] Management module 15 then determines a classification of the
inventory holder 30 to be stored at step 610. This classification
of inventory holder 30 may describe any appropriate characteristic,
attribute, or value or collection of characteristics, attributes,
or values associated with the relevant inventory holder 30. In
particular embodiments, management module 15 determines the
classification by determining a holder velocity of the inventory
holder 30 that specifies the frequency with which the inventory
items 40 stored in the relevant inventory holder 30 are requested
in retrieval requests received by management module 15.
[0110] At step 620, management module 15 determines a
classification associated with each of a plurality of storage
locations 90. This classification of inventory holder 30 may
describe any appropriate characteristic, attribute, or value or
collection of characteristics, attributes, or values associated
with the relevant storage location 90. In particular embodiments,
management module 15 determines these classifications by
determining a range of holder velocities associated with each
storage location 90. For example, management module 15 may divide
storage locations 90 into a plurality of storage regions 100 and
assign a range of holder velocities to each storage region 100
based on appropriate criteria, such as the distance between the
storage locations and one or more inventory stations. This may
allow management module 15 to assign inventory holders 30 with less
frequently requested inventory items 40 to storage regions 100
further removed from inventory stations 50. Although, in the
described embodiment, management module 15 determines the
classifications of the relevant storage locations 90 at the time of
the storage operation, in alternative embodiments, management
module 15 may determine the classifications of the relevant storage
locations 90 at other appropriate times and store these
classifications for use during subsequent storage operations.
[0111] At step 630, management module 15 selects an available
storage location 90 for the inventory holder 30 to be stored based
on the classification of the relevant inventory holder 30 and the
classification of the selected storage location 90. For example, in
particular embodiments, management module 15 identifies a storage
region 100 that is assigned a range of holder velocities that
includes the holder velocity of the relevant inventory holder 30.
Management module 15 then selects an available storage location 90
from the identified storage region 100.
[0112] After selecting a storage location 90, management module 15
may reserve the selected storage location 90, at step 640, for use
by the inventory holder 30 to be stored. Management module 15 may
reserve the selected storage space 90, in any appropriate manner
based on the configuration of inventory system 10. For example, in
particular embodiments, management module 15 maintains a map of all
storage locations 90 that indicates whether a particular storage
location 90 is available for use. In such embodiments, management
module 15 may reserve the selected storage location 90 by marking
the selected storage location 90 as unavailable on the map. At step
650, management module 15 transmits information identifying the
storage location 90 to a mobile drive unit 20 associated with the
inventory holder 30. For example, if inventory holder 30 was just
involved in a retrieval request, the associated mobile drive unit
20 may be the mobile drive unit 20 that moved that inventory holder
30 to the inventory station 50 where the retrieval request was
fulfilled.
[0113] After management module 15 has transmitted this information
to the associated mobile drive unit 20, appropriate elements of
inventory system 10 may perform appropriate actions to complete the
storage operation. In particular embodiments, the associated mobile
drive unit 20 moves the inventory holder 30 to the selected storage
location 90. The associated mobile drive unit 20 then uncouples
from the inventory holder 30. The associated mobile drive unit 20
then moves away, leaving the inventory holder 30 behind in the
selected storage location 90.
[0114] FIG. 7 is a flowchart illustrating example functionality of
a particular embodiment of management module 15 in executing a
replenishment operation. The method begins at step 700 with
management module 15 receiving an inventory request that identifies
an inventory item 40 to be stored in inventory system 10. In
response to receiving the inventory request, management module 15
determines a classification of the inventory item to be stored. In
particular, in the described embodiment, management module 15
determines the classification of the inventory item 40 to be stored
by calculating an item velocity for the inventory item 40 to be
stored at step 710. In particular embodiments, this item velocity
is calculated based, at least in part, on a frequency with which
the inventory item 40 to be stored is requested in inventory
requests received by management module 15 and/or other elements of
inventory system 10.
[0115] At step 720, management module 15 identifies a plurality of
inventory holders 30 with unused storage capacity. In particular
embodiments, the inventory holders 30 with unused storage capacity
may represent inventory holders 30 having an empty storage bin,
inventory holders 30 having unused storage capacity in a storage
bin currently storing the inventory item 40 to be stored, or
inventory holders 30 with any other form of unused capacity.
Management module 15 then determines a classification for each of
the plurality of inventory holders 30 with unused capacity. More
specifically, in the described embodiment, management module 15
determines the classifications of the relevant inventory holders 30
calculating a holder velocity for each of the inventory holders 30
with unused capacity at step 730.
[0116] Management module 15 selects an inventory holder 30 from the
inventory holders having unused storage capacity based, at least in
part, on the classification of the inventory item to be stored and
a classification of one or more other inventory items 40 currently
stored in the selected inventory holder 30. In the described
embodiment, management module 15 selects the inventory holder 30,
at step 740, based on the holder velocity of the selected inventory
holder 30 and the item velocity of the inventory item 40 to be
stored. In particular embodiments, management module 15 may also
select an inventory holder 30 based on the usefulness value
described above, and/or on any other values, criteria,
characteristics, or factors associated with the relevant inventory
holders 30.
[0117] At step 750, management module 15 allocates, to the selected
inventory holder 30, a first portion of a replenish quantity of the
inventory item 40 to be stored. In particular embodiments,
inventory holder 30 may allocate a portion equal to the unused
storage capacity possessed by the selected inventory holder 30. At
step 760, management module 15 determines whether any portion of
replenish quantity remains after the first portion has been
allocated to the selected inventory holder 30. If so, management
module 15 may repeat steps 740-760, selecting additional inventory
holders 30 until all of the replenish quantity is allocated.
[0118] Once management module 15 has allocated all of the replenish
quantity to particular inventory holders 30, management module 15
transmits to one or more mobile drive unit 20 , information
identifying the selected inventory holder(s) 40 at step 770. If
management module 15 has selected multiple inventory holders 30, in
particular embodiments, management module 15 may transmit multiple
sets of information, with each set of information transmitted to a
different mobile drive unit 20 and each set identifying a different
one of the selected inventory holders 30. At step 780, management
module 15 may also transmit information identifying an inventory
station 50 at which the replenishment request will be completed to
the relevant mobile drive units 20. Management module 15 may select
the inventory station 50 based on any suitable criteria, receive
information identifying the inventory station 50 as part of the
replenishment request, and/or determine the inventory station 50 to
be used in completing the replenishment request in any other manner
appropriate based on the configuration of inventory system 10. The
relevant mobile drive units 20 may then move the selected inventory
holder(s) 30 to the inventory station 50 at which the replenishment
will be completed.
[0119] Additionally, in particular embodiments, management module
15 may also execute certain steps to facilitate the return of the
selected inventory holders 30 to storage after the inventory items
40 in question have been stored in the selected inventory holders
30. For example, in the described embodiment, management module 15
receives information indicating the inventory item 40 to be stored
has been stored in the selected inventory holder(s) 30 at step 790.
At step 800, management module 15 determines a storage location for
the selected inventory holder(s) 30. In particular embodiments, if
management module 15 has selected multiple inventory holders 30 to
complete the replenishment request, management module 15 may
determine a storage location for each of the selected inventory
holders 30. At step 810, management module 15 transmits information
identifying the storage location determined for the selected
inventory holders 30 to one or more mobile drive units 20. In
particular embodiments, if management module 15 has selected
multiple inventory holders 30, management module 15 may transmit
information identifying the storage location determined for each of
the selected inventory holders 30 to a mobile drive unit 20
associated with that inventory holder 30. These mobile drive units
20 may then move the selected inventory holders 30 to the storage
locations determined by management module 15. In alternative
embodiments, a single mobile drive unit 20 may be responsible for
returning all inventory holders 30 to storage and management module
15 may transmit information identifying storage locations for all
of the selected inventory holders 30 to that one mobile drive unit
20. That mobile drive unit 20 may then move each of the selected
inventory holders 30 to the storage location selected for that
inventory holder 30.
[0120] Although FIGS. 5-7 illustrate steps executed by particular
embodiments of management module 15 in a particular order,
alternative embodiments of management module 15 may perform all,
some, or none of these steps and may do so in any appropriate
order. Moreover, any two or more of the steps illustrated in any of
FIGS. 5-7 may be combined, modified or deleted where appropriate
and additional steps may also be added. Furthermore, although the
present invention has been described with several embodiments, a
myriad of changes, variations, alterations, transformations, and
modifications may be suggested to one skilled in the art, and it is
intended that the present invention encompass such changes,
variations, alterations, transformations, and modifications as fall
within the scope of the appended claims.
* * * * *