Note: Descriptions are shown in the official language in which they were submitted.
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ROBOT QUEUING IN ORDER FULFILLMENT OPERATIONS
CROSS-REFERENCE TO RELATED APPLICATION(S)
This application claims priority to U.S. Application No. 15/697,759, filed
September 7, 2017, which is a continuation in part of U.S. Application No.
15/628,751,
filed on June 21, 2017, which is a continuation of U.S. Application No.
15/081,124, filed
on March 25, 2016, and issued as U.S. Patent No. 9,776,324 on October 3, 2017.
FIELD OF THE INVENTION
This invention relates to robot-assisted product order-fulfillment systems and
methods and more particularly to queueing of robots destined for a common
location(s)
using one or more queue groups.
BACKGROUND OF THE INVENTION
Ordering products over the intemet for home delivery is an extremely popular
way
of shopping. Fulfilling such orders in a timely, accurate and efficient manner
is logistically
challenging to say the least. Clicking the "check out" button in a virtual
shopping cart
creates an "order." The order includes a listing of items that are to be
shipped to a particular
address. The process of "fulfillment" involves physically taking or "picking"
these items
from a large warehouse, packing them, and shipping them to the designated
address. An
important goal of the order-fulfillment process is thus to ship as many items
in as short a
time as possible.
The order-fulfillment process typically takes place in a large warehouse that
contains many products, including those listed in the order. Among the tasks
of order
fulfillment is therefore that of traversing the warehouse to find and collect
the various items
listed in an order. In addition, the products that will ultimately be shipped
first need to be
received in the warehouse and stored or "placed" in storage bins in an orderly
fashion
throughout the warehouse so they can be readily retrieved for shipping.
In a large warehouse, the goods that are being delivered and ordered can be
stored
in the warehouse very far apart from each other and dispersed among a great
number of
other goods. With an order-fulfillment process using only human operators to
place and
pick the goods requires the operators to do a great deal of walking and can be
inefficient
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and time consuming. Since the efficiency of the fulfillment process is a
function of the
number of items shipped per unit time, increasing time reduces efficiency.
In order to increase efficiency, robots may be used to perform functions of
humans
or they may be used to supplement the humans' activities. For example, robots
may be
assigned to "place" a number of items in various locations dispersed
throughout the
warehouse or to "pick" items from various locations for packing and shipping.
The picking
and placing may be done by the robot alone or with the assistance of human
operators. For
example, in the case of a pick operation, the human operator would pick items
from shelves
and place them on the robots or, in the case of a place operation, the human
operator would
pick items from the robot and place them on the shelves.
With numerous robots navigating a space it is very possible and even likely
that
robots will attempt to navigate to a position that is occupied by another
robot, resulting in
a race condition. Race conditions are when two robots are attempting to get to
the same
place and become processor bound as they attempt to reconcile the changing
external
environment. Race conditions are very undesirable and can result the robots
being unable
to perform further operations until the condition is resolved.
BRIEF SUMMARY OF THE INVENTION
In one aspect the invention features a method for queuing robots destined for
one
or more target locations in an environment. The method includes determining if
a plurality
of robots destined for the one or more target locations have entered a
predefined target zone
proximate the one or more target locations. The method also includes assigning
each of
the robots to either its target location or one of a plurality of queue
locations based on an
assigned priority. The plurality of queue locations are grouped into one or
more queue
groups.
In other aspects of the invention one or more of the following features may be
included. The environment may be a warehouse space containing items for
customer order
fulfillment. The assigned priority may be determined by the order of entry of
each of the
plurality of robots into the target zone, and wherein the first robot to enter
the target zone
is assigned the highest priority. The assigned priority may be determined by
one or both
of the order of entry of each of the plurality of robots into the target zone
and an order
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priority associated with a customer order to be processed by each of the
plurality of robots.
The order priority may be associated with the customer order to be processed
by each of
the plurality of robots is determined by one or more of the following:
shipping priority,
item type, customer type, or retailer. The plurality of queue locations may be
grouped into
at least two queue groups spaced from each other in the environment. There may
be
included a first plurality of queue locations in a first group and a second
plurality of queue
locations in a second queue group, wherein the first plurality of queue
locations in the first
group and a second plurality of queue locations in a second queue group are
all associated
with one target location. The plurality of queue locations may be grouped into
one queue
group and the plurality of que locations may be associated with a plurality of
target
locations. The first plurality of queue locations in the first group and a
second plurality of
queue locations in a second queue group may be associated with a plurality of
target
locations. The one or more target locations and the plurality of queue
locations may be
each defined by a pose to which the robot is capable of navigating.
In yet another aspect, the invention features a robot capable of navigating to
predefined locations in an environment containing a plurality of other robots;
the robot and
the plurality of other robots capable of interacting with a management system.
The robot
includes a mobile base and a communication device enabling communication
between the
robot and the management system. There is a processor, responsive to
communications
with the management system, configured to navigate the robot to a target
location in the
environment. The processor is also configured to determine if at least one of
the plurality
of other robots occupies the target location. If it is determined that at
least one of the
plurality of other robots occupies the target location, the processor
determines if the robot
has entered a predefined target zone proximate the target location. If it is
determined that
the robot has entered the predefined target zone, the processor is configured
to assign the
robot to one of a plurality of queue locations based on an assigned priority.
The plurality
of queue locations are grouped in one or more queue groups.
In further aspects of the invention one or more of the following features may
be
included. The environment may be a warehouse space containing items for
customer order
fulfillment. The assigned priority may be determined by the order of entry of
each of the
plurality of robots into the target zone. The first robot to enter the target
zone may be
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assigned the highest priority. The assigned priority may be determined by one
or both of
the order of entry of each of the plurality of robots into the target zone and
an order priority
associated with a customer order to be processed by each of the plurality of
robots. The
order priority associated with the customer order to be processed by each of
the plurality
of robots may be determined by one or more of the following: shipping
priority, item type,
customer type, or retailer. The plurality of queue locations may be grouped
into at least
two queue groups spaced from each other in the environment. There may be a
first plurality
of queue locations in a first group and a second plurality of queue locations
in a second
queue group, wherein the first plurality of queue locations in the first group
and a second
plurality of queue locations in a second queue group may be all associated
with one target
location. The plurality of queue locations may be grouped into one queue group
and the
plurality of que locations may be associated with a plurality of target
locations. The first
plurality of queue locations in the first group and a second plurality of
queue locations in
a second queue group may be associated with a plurality of target locations.
The one or
more target locations and the plurality of queue locations may be each defined
by a pose
to which the robot is capable of navigating.
In accordance with an aspect, there is provided a method for queuing mobile
robots
destined for one or more occupied target locations in a warehouse space,
comprising:
determining if a plurality of mobile robots moving toward the one or more
target
locations in the warehouse space have entered a predefined target zone
proximate the one or more target locations; and
causing each of the plurality of mobile robots to move to and occupy one of a
plurality
of queue locations in the warehouse space based on an assigned priority;
wherein the assigned priority is determined by one or both of the order of
entry
of each of the plurality of mobile robots into the target zone and an order
priority
associated with a customer order to be processed by each of the plurality of
mobile robots;
wherein the plurality of queue locations are grouped into one or more queue
groups
spaced from the one or more target locations in the warehouse space.
In accordance with an aspect, there is provided a mobile robot capable of
navigating
to predefined locations in a warehouse space containing a plurality of other
mobile robots,
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the mobile robot and the plurality of other mobile robots capable of
interacting with a
management system, the mobile robot comprising:
a mobile base;
a communication device enabling communication between the mobile robot and
the management system;
a processor, responsive to communications with the management system,
configured to:
navigate the mobile robot to a target location in the warehouse
space;
determine if at least one of the plurality of other mobile robots
occupies the target location, determine if the mobile robot
has entered a predefined target zone proximate the target
location;
if it is determined that at least one of the plurality of other mobile
robots occupies the target location, determine if the mobile
robot has entered a predefined target zone proximate the
target location;
if it is determined that the robot has entered the predefined target
zone, cause the mobile robot to move to and occupy one of
a plurality of queue locations in the warehouse space based
on an assigned priority; wherein the assigned priority is
determined by one or both of the order of entry of the mobile
robot relative to each of the plurality of other mobile robots
into the target zone and an order priority associated with a
customer order to be processed by the mobile robot and each
of the plurality of other mobile robots; and wherein the
plurality of queue locations are grouped in one or more
queue groups spaced from the target location in the
warehouse space.
These and other features of the invention will be apparent from the following
detailed description and the accompanying figures, in which:
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BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a top plan view of an order-fulfillment warehouse;
FIG. 2 is a perspective view of a base of one of the robots used in the
warehouse shown in
FIG. 1;
FIG. 3 is a perspective view of the robot in FIG. 2 outfitted with an armature
and parked
in front of a shelf shown in FIG. 1;
FIG. 4 is a partial map of the warehouse of FIG. 1 created using laser radar
on the robot;
FIG. 5 is a flow chart depicting the process for locating fiducial markers
dispersed
throughout the warehouse and storing fiducial marker poses;
FIGS. 6 is a table of the fiducial identification to pose mapping;
FIG. 7 is a table of the bin location to fiducial identification mapping;
FIG. 8 is a flow chart depicting product SKU to pose mapping process;
FIG. 9 is a schematic view of the target and queue locations used in the
queuing process
according to an aspect of this invention;
FIG. 10 is a flow chart depicting the robot queuing process according to an
aspect of this
invention;
FIG. 11 is a schematic view of the target and queue locations in an another
aspect of
queuing process according to this invention in which a split queue is used;
FIG. 12 depicts the target and queue locations of Fig. 11 with robots being
directed to
designated queue locations based on assigned priorities according to an aspect
of this
invention;
FIG. 13 is a schematic view of the target and queue locations in an another
aspect of
queuing process according to this invention in which a shared queue is used;
and
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FIG. 14 is a schematic view of the target and queue locations in an another
aspect of
queuing process according to this invention in which both a shared queue and
split queue
are used.
DETAILED DESCRIPTION OF INVENTION
The disclosure and the various features and advantageous details thereof are
explained more fully with reference to the non-limiting embodiments and
examples that
are described and/or illustrated in the accompanying drawings and detailed in
the following
description. It should be noted that the features illustrated in the drawings
are not
necessarily drawn to scale, and features of one embodiment may be employed
with other
embodiments as the skilled artisan would recognize, even if not explicitly
stated herein.
Descriptions of well-known components and processing techniques may be omitted
so as
to not unnecessarily obscure the embodiments of the disclosure. The examples
used herein
are intended merely to facilitate an understanding of ways in which the
disclosure may be
practiced and to further enable those of skill in the art to practice the
embodiments of the
disclosure. Accordingly, the examples and embodiments herein should not be
construed as
limiting the scope of the disclosure. Moreover, it is noted that like
reference numerals
represent similar parts throughout the several views of the drawings.
The invention is directed to a system and method for queueing robots destined
for a
common target location. Although not restricted to any particular robot
application, one
suitable application that the invention may be used in is order fulfillment.
The use of robots
in this application will be described to provide context for the system and
method for
queueing robots but is not limited to that application.
Referring to FIG. 1, a typical order-fulfillment warehouse 10 includes shelves
12
filled with the various items that could be included in an order 16. In
operation, the order
16 from warehouse management server 15 arrives at an order-server 14. The
order-server
14 communicates the order 16 to a robot 18 selected from a plurality of robots
that roam
the warehouse 10.
In a preferred embodiment, a robot 18, shown in FIG. 2, includes an autonomous
wheeled base 20 having a laser-radar 22. The base 20 also features a
transceiver 24 that
enables the robot 18 to receive instructions from the order-server 14, and a
camera 26. The
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base 20 also features a processor 32 that receives data from the laser-radar
22 and the
camera 26 to capture information representative of the robot's environment and
a memory
34 that cooperate to carry out various tasks associated with navigation within
the
warehouse 10, as well as to navigate to fiducial marker 30 placed on shelves
12, as shown
in FIG. 3. Fiducial marker 30 (e.g. a two-dimensional bar code) corresponds to
bin/location
of an item ordered. The navigation approach of this invention is described in
detail below
with respect to Figs. 4-8.
While the initial description provided herein is focused on picking items from
bin
locations in the warehouse to fulfill an order for shipment to a customer, the
system is
equally applicable to the storage or placing of items received into the
warehouse in bin
locations throughout the warehouse for later retrieval and shipment to a
customer. The
invention is also applicable to inventory control tasks associated with such a
warehouse
system, such as, consolidation, counting, verification, inspection and clean-
up of products.
As described in more detail below, robots 18 can be utilized to perform
multiple
tasks of different task types in an interleaved fashion. This means that robot
18, while
executing a single order traveling throughout the warehouse 10, may be picking
items,
placing items, and performing inventory control tasks. This kind of
interleaved task
approach can significantly improve efficiency and performance.
Referring again to FIG.2, An upper surface 36 of the base 20 features a
coupling
38 that engages any one of a plurality of interchangeable armatures 40, one of
which is
shown in FIG. 3. The particular armature 40 in FIG. 3 features a tote-holder
42 for carrying
a tote 44 that receives items, and a tablet holder 46 for supporting a tablet
48. In some
embodiments, the armature 40 supports one or more totes for carrying items. In
other
embodiments, the base 20 supports one or more totes for carrying received
items. As used
herein, the term "tote" includes, without limitation, cargo holders, bins,
cages, shelves, rods
from which items can be hung, caddies, crates, racks, stands, trestle,
containers, boxes,
canisters, vessels, and repositories.
Although a robot 18 excels at moving around the warehouse 10, with current
robot
technology, it is not very good at quickly and efficiently picking items from
a shelf and
placing them on the tote 44 due to the technical difficulties associated with
robotic
manipulation of objects. A more efficient way of picking items is to use a
local operator
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50, which is typically human, to carry out the task of physically removing an
ordered item
from a shelf 12 and placing it on robot 18, for example, in tote 44. The robot
18
communicates the order to the local operator 50 via the tablet 48, which the
local operator
50 can read, or by transmitting the order to a handheld device used by the
local operator
50.
Upon receiving an order 16 from the order server 14, the robot 18 proceeds to
a
first warehouse location, e.g. shown in FIG. 3. It does so based on navigation
software
stored in the memory 34 and carried out by the processor 32. The navigation
software relies
on data concerning the environment, as collected by the laser-radar 22, an
internal table in
memory 34 that identifies the fiducial identification ("ID") of fiducial
marker 30 that
corresponds to a location in the warehouse 10 where a particular item can be
found, and
the camera 26 to navigate.
Upon reaching the correct location, the robot 18 parks itself in front of a
shelf 12
on which the item is stored and waits for a local operator 50 to retrieve the
item from the
shelf 12 and place it in tote 44. If robot 18 has other items to retrieve it
proceeds to those
locations. The item(s) retrieved by robot 18 are then delivered to a packing
station 100,
Fig. 1, where they are packed and shipped.
It will be understood by those skilled in the art that each robot may be
fulfilling one
or more orders and each order may consist of one or more items. Typically,
some form of
route optimization software would be included to increase efficiency, but this
is beyond
the scope of this invention and is therefore not described herein.
In order to simplify the description of the invention, a single robot 18 and
operator
50 are described. However, as is evident from FIG. 1, a typical fulfillment
operation
includes many robots and operators working among each other in the warehouse
to fill a
continuous stream of orders.
The navigation approach of this invention, as well as the semantic mapping of
a
SKU of an item to be retrieved to a fiducial ID/pose associated with a
fiducial marker in
the warehouse where the item is located, is described in detail below with
respect to Figs.
4-8.
Using one or more robots 18, a map of the warehouse 10 must be created and the
location of various fiducial markers dispersed throughout the warehouse must
be
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determined. To do this, one of the robots 18 navigates the warehouse and
builds a map
10a, FIG. 4, utilizing its laser-radar 22 and simultaneous localization and
mapping (SLAM), which is a computational problem of constructing or updating a
map of
an unknown environment. Popular SLAM approximate solution methods include
the particle filter and extended Kalman filter. The SLAM GMapping approach is
the
preferred approach, but any suitable SLAM approach can be used.
Robot 18 utilizes its laser-radar 22 to create map 10a of warehouse 10 as
robot 18
travels throughout the space identifying, open space 112, walls 114, objects
116, and other
static obstacles, such as shelf 12, in the space, based on the reflections it
receives as the
laser-radar scans the environment.
While constructing the map 10a or thereafter, one or more robots 18 navigates
through warehouse 10 using camera 26 to scan the environment to locate
fiducial markers
(two-dimensional bar codes) dispersed throughout the warehouse on shelves
proximate
bins, such as 32 and 34, FIG. 3, in which items are stored. Robots 18 use a
known starting
point or origin for reference, such as origin 110. When a fiducial marker,
such as fiducial
marker 30, FIGS. 3 and 4, is located by robot 18 using its camera 26, the
location in the
warehouse relative to origin 110 is determined.
By the use of wheel encoders and heading sensors, vector 120, and the robot's
position in the warehouse 10 can be determined. Using the captured image of a
fiducial
marker/two-dimensional barcode and its known size, robot 18 can determine the
orientation with respect to and distance from the robot of the fiducial
marker/two-
dimensional barcode, vector 130. With vectors 120 and 130 known, vector 140,
between
origin 110 and fiducial marker 30, can be determined. From vector 140 and the
determined
orientation of the fiducial marker/two-dimensional barcode relative to robot
18, the pose
(position and orientation) defined by a quaternion (x, y, z, co) for fiducial
marker 30 can be
determined.
Flow chart 200, Fig. 5, describing the fiducial marker location process is
described.
This is performed in an initial mapping mode and as robot 18 encounters new
fiducial
markers in the warehouse while performing picking, placing and/or other tasks.
In step
202, robot 18 using camera 26 captures an image and in step 204 searches for
fiducial
markers within the captured images. In step 206, if a fiducial marker is found
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(step 204) it is determined if the fiducial marker is already stored in
fiducial table 300, Fig.
6, which is located in memory 34 of robot 18. If the fiducial information is
stored in
memory already, the flow chart returns to step 202 to capture another image.
If it is not in
memory, the pose is determined according to the process described above and in
step 208,
it is added to fiducial to pose lookup table 300.
In look-up table 300, which may be stored in the memory of each robot, there
are
included for each fiducial marker a fiducial identification, 1, 2, 3, etc, and
a pose for the
fiducial marker/bar code associated with each fiducial identification. The
pose consists of
the x,y,z coordinates in the warehouse along with the orientation or the
quaternion (x,y,z,
w).
In another look-up Table 400, Fig. 7, which may also be stored in the memory
of
each robot, is a listing of bin locations (e.g. 402a-f) within warehouse 10,
which are
correlated to particular fiducial ID's 404, e.g. number "11". The bin
locations, in this
example, consist of seven alpha-numeric characters. The first six characters
(e.g. L01001)
pertain to the shelf location within the warehouse and the last character
(e.g. A-F) identifies
the particular bin at the shelf location. In this example, there are six
different bin locations
associated with fiducial ID "11". There may be one or more bins associated
with each
fiducial ID/marker.
The alpha-numeric bin locations are understandable to humans, e.g. operator
50,
Fig. 3, as corresponding to a physical location in the warehouse 10 where
items are stored.
However, they do not have meaning to robot 18. By mapping the locations to
fiducial ID's,
Robot 18 can determine the pose of the fiducial ID using the information in
table 300, Fig.
6, and then navigate to the pose as described herein.
The order fulfillment process according to this invention is depicted in flow
chart
500, Fig. 8. In step 502, warehouse management system 15, Fig. 1, obtains an
order, which
may consist of one or more items to be retrieved. In step 504 the SKU
number(s) of the
items is/are determined by the warehouse management system 15, and from the
SKU
number(s), the bin location(s) is/are determined in step 506. A list of bin
locations for the
order is then transmitted to robot 18. In step 508, robot 18 correlates the
bin locations to
fiducial ID's and from the fiducial ID's, the pose of each fiducial ID is
obtained in step
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510. In step 512 the robot 18 navigates to the pose as shown in Fig. 3, where
an operator
can pick the item to be retrieved from the appropriate bin and place it on the
robot.
Item specific information, such as SKU number and bin location, obtained by
the
warehouse management system 15, can be transmitted to tablet 48 on robot 18 so
that the
operator 50 can be informed of the particular items to be retrieved when the
robot arrives
at each fiducial marker location.
With the SLAM map and the pose of the fiducial ID's known, robot 18 can
readily
navigate to any one of the fiducial ID's using various robot navigation
techniques. The
preferred approach involves setting an initial route to the fiducial marker
pose given the
knowledge of the open space 112 in the warehouse 10 and the walls 114, shelves
(such as
shelf 12) and other obstacles 116. As the robot begins to traverse the
warehouse using its
laser radar 26, it determines if there are any obstacles in its path, either
fixed or dynamic,
such as other robots 18 and/or operators 50, and iteratively updates its path
to the pose of
the fiducial marker. The robot re-plans its route about once every 50
milliseconds,
constantly searching for the most efficient and effective path while avoiding
obstacles.
With the product SKU/fiducial ID to fiducial pose mapping technique combined
with the SLAM navigation technique both described herein, robots 18 are able
to very
efficiently and effectively navigate the warehouse space without having to use
more
complex navigation approaches typically used which involve grid lines and
intermediate
fiducial markers to determine location within the warehouse.
As described above, a problem that can arise with multiple robots navigating a
space is called a "race condition", which can occur if one or more robots
attempt to navigate
to a space occupied by another robot. With this invention, alternative
destinations for the
robots are created to place them in a queue and avoid race conditions from
occuring. The
process is depicted in Fig. 9, where robot 600 is shown positioned at a target
location/pose
602. Pose 602 could correspond to any location in a warehouse space, for
example, a
packing or loading station or a position near a particular bin. When other
robots try to
navigate to pose 602, such as robots 604, 606, and 608 (as indicated by the
dotted lines
from the robots and terminating at pose 602) they are redirected to temporary
holding
locations, such as locations or queue slots 610, 612, and 614.
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Queue slots or locations 610, 612, and 614 are offset from pose 612. In this
example queue slot 610 is offset from pose 602 by a distance x, which could
be, for
example, one (1) meter. Queue slot 612 is offset from queue slot 610 by an
additional
distance x and queue slot 614 is offset another distance x from queue slot
612. While, in
this example, the distances are uniformly spaced along a straight line
emanating from pose
602, this is not a requirement of the invention. The locations of the queue
slots may be
non-uniforn and variable given the dynamic environment of the warehouse. The
queue
slots maybe offset according to an queuing algorithm that observes the
underlying global
map and the existing obstacles and constraints of the local map. The queuing
algorithm
may also consider the practical limits of queuing in the space proximate the
target
location/pose to avoid blocking traffic, interfering with other locations, and
creating new
obstacles.
In addition, the proper queue slotting of robots into the queue must be
managed. In
the example shown in Fig. 9, the robot with the first priority to occupy the
pose 602 is
queued in the first queue slot 610, while the other robots are queued in the
other queue slots
based on their respective priorities. Priorities are determined by the order
of the robots'
entry into a zone 618 proximate pose 602. In this case, zone 618 is defined by
a radius, R,
about pose 602, which in this case is approximately three (3) meters (or 3x).
The first robot
to enter the zone, in this case 604, has the highest priority and is assigned
the first queue
slot, queue slot 610. When robot 606, which is closer to zone 618 than robot
608, enters
zone 618, assuming that robot 600 is still at pose 602 and robot 604 is
located at queue slot
610, it has the next highest priority and it is therefore assigned queue slot
612. When robot
608 then enters zone 618, assuming that robot 600 is still at pose 602 and
robots 604 and
606 are still located at queue slots 610 and 612, respectively, it is assigned
to queue slot
614.
When robot 600 moves from pose 602 (target location), robot 604 moves from
queue slot 610 to pose 602. Robots 606 and 608 move to queue slot positions
610 and 612,
respectively. The next robot to enter zone 618 would be positioned in queue
slot position
614. Of course, additional number of queue slot positions could be included to
accommodate expected traffic flows.
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The manner in which the robots are navigated to the queue slots and ultimately
the
target location is accomplished by temporarily redirecting them from the pose
of the target
location to the pose(s) of the queue slot(s). In other words, when it is
determined that a
robot must be placed in a queue slot, its target pose is temporarily adjusted
to a pose
corresponding to the location of the queue slot to which it is assigned. As it
moves up in
position in the queue, the pose is again adjusted temporarily to the pose of
the queue slot
with the next highest priority until it is able to reach its original target
location at which
time the pose is reset to the original target pose.
Flow chart 700, Fig. 10, depicts the robot queuing process implemented by WMS
15 for a particular pose (target pose) within the warehouse. At step 702, it
is determined if
the target pose is occupied by a robot. If it is not, the process returns to
step 702 until there
is a robot occupying the target pose. When a robot is occupying the target
pose, the process
determines at step 704 if there is another robot in the target zone or if
there is a robot in
one or more of the queue slots. If it is determined that there is no robot in
the target zone
or in one or more queue slots, the process returns to step 702. If it is
determined that there
is a robot occupying the target pose or if the queue slot(s) is/are occupied,
then at step 706
the robots are assigned to the appropriate queue slots.
If there is a robot in the target zone but no robot in the queue slots, then
the robot
in the target zone is directed to occupy the first queue slot, i.e. queue slot
610, Fig. 9. If
there is a robot in the target zone and a robot (or multiple robots in the
queue slots) then
the robot in the target zone is slotted into the next available queue slot, as
described above.
If there is no robot in the target zone but there is/are robot(s) in the queue
slot(s), then the
slotted robots remain in the same positions. At step 708, if it is determined
that the target
pose is not occupied, then the robots in the queue slots are moved up a
position, i.e. queue
slot 610 to the target pose, queue slot 612 to queue slot 610 and so forth. If
the target pose
is still occupied, the process returns to step 704.
In Fig. 9, the queue locations 610, 612, and 614 are in line and adjacent to
each
other. This is acceptable for many situations, but in areas within a warehouse
environment
where there is limited space or heavy traffic or when many queue locations are
needed, it
may be desirable to utilize a "split" queue. An example of this is shown in
Fig. 11. Here,
a station 800 having a target location 802 is shown. Station 800 may be an
induction station
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attended by an operator where a robot is assigned a customer order to fill and
provided
with a tote to carry the order or it may be a packing station where the robot
is dropping off
a customer order for packing and shipment by an operator. The target location
does not
need to be associated with a station, but it is a typical situation where
multiple robots may
be simultaneously vying for a common target location.
Referring again to Fig. 11, queue locations 804, 806 and 808 are part of a
first queue
group 810 and are shown spaced from target location 802. In this example,
additional
queue locations are required, but there is limited space as queue group 810 is
adjacent to a
busy path of traffic traversed by robots, such as robot 814, and operators. To
overcome
this issue, there is formed a second queue group 816, including additional
queue locations
818, 820, and 822, physically spaced from queue group 810 across path 812. The
queue
locations in the two queue groups 810 and 816, even though physically
separated, together
form a single queue for target location 802. It should be noted that while
there are two
queue groups each with three queue locations, any number of queue groups
having any
number of queue locations may be used in accordance with the disclosure
herein.
Just as with Fig. 9, in the example of in Fig. 11, assuming the target
location 802
(labelled "T") is occupied by a robot being serviced at station 802, robots
entering a
predefined target zone 803, defined by a dashed-line, are assigned to queue
locations based
on priorities assigned to them by the system. Queue location 804, labelled
"1", is the
highest priority queue location. Queue locations 806-822 have lower/decreasing
priority
levels, as indicated by their labels "2"-"6". Thus, the robot with the first
or highest priority
to occupy the target location 802, when it is available, is directed to queue
location 804,
while the other robots are queued in the other queue slots based on their
respective
priorities. Priorities may be determined by the order of the robots' entry
into the predefined
target zone. In other words, the earlier the entry into the target zone, the
higher the assigned
priority for the robot and thus the lower the queue number.
The assigned priorities may be established in other ways. For example, instead
of
or in combination with the time of entering into the target zone, priority can
be assigned
based on the customer order to be processed by the robots. The customer order
for each
robot may be assigned a priority based on one or more of the following
criteria: shipping
priority, item type, customer type, or retailer, for example. Customer orders
with expedited
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delivery or preferred customers may be assigned a high priority and therefore
be placed in
higher priority queue locations to ensure faster processing. Similarly,
certain products or
retailers could be given priority based on contractual relationships. The
priority of the
customer order alone or in combination with the priority based on the time of
entering into
the target zone may be used to assign priority and hence queue location to the
robots vying
for the common target location.
Continuing to refer to Fig. 11, there are shown two robots 824 and 826 which
have
entered the predefined target zone 803. Robot 824 has been assigned a priority
of (1,B)
and robot 826 has been assigned a priority of (2,A). In this example the first
priority criteria
is numerical and indicates the order in which the robots entered the target
zone 803, i.e.
robot 824 entered first and robot 826 entered second. If the order of entry
was the only
criteria, robot 824 would be assigned to queue location 804 and robot 826
would be
assigned to queue location 806. However, in this example there is a second
criteria related
to the customer order, e.g. shipping priority, item type, customer type, or
retailer. Robot
824 has been assigned a "B" priority regarding its customer order while robot
826 has been
assigned an "A" priority. In this example, the customer order priority trumps
the order of
entry into the target zone so, as indicted by lines 825 and 827, robot 824 is
directed to
queue location 806 (location "2") and robot 826 is directed to queue location
804 (location
cc1,,).
This above example is just one simple example of priority assignment and any
suitable method for assigning priority may be used in connection with this
invention using
the standard queue shown in Fig. 9, the split queue of Fig. 11 and the
shared/split queues
described below in Figs. 12 and 13.
In another embodiment, shown in Fig. 12, another aspect of the disclosure is
described. Here, a "shared" queue 830 may be used. What is meant by "shared"
in this
context is that queue group 830 is shared among a number of target locations,
such as target
locations 832, 834, and 836, which are associated with and proximate to
stations 838, 840,
and 842, respectively. Robots that are destined for any of target locations
832, 834 or 836
are directed to one of the queue locations 850-858, which have priorities 1-9,
respectively.
This means that queue location 850 (priority "1") is the location where the
robot with the
highest priority would be located irrespective of the target location for
which it is destined
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and queue location 9 (priority "9") is the queue location where the robot with
the lowest
priority would be directed.
Stations 838 ("A"), 840 ("B"), and 842 ("C"), may be configured to perform the
same or different functions. For example, the may all be configured as
induction stations
or packing stations or they may be configured as a combination of induction
and packing
stations. Moreover, any number of stations and any number of queue locations
in queue
group 830 may be used. In one scenario, stations 838, 840, and 842 may be
configured
such that any robot in the queue locations can proceed to any target
location/station. In
that case, as indicated by solid line 864, a robot positioned in queue
location 850 would
proceed to the first available target location which in this example is target
location 832.
Target locations 834 and 836 are shown to be occupied by robots 860 and 862,
respectively.
The robots in the other queue locations will all move up to the next highest
priority queue
location.
Alternatively, for various reasons, certain robots may only be able to proceed
to
certain stations/target locations. This scenario is depicted in Fig. 12 by the
dashed line
866, which shows the robot in queue location 851 (priority "2") proceeding to
open target
location 832 instead of the robot in queue location 850 (priority "1"). This
may be because
the robot at queue location 850 is not able to be serviced by station 838
(e.g. the robot
needs to be inducted but station 838 is dedicated to packaging/delivery). As
shown by
dashed line 868, when robot 860 leaves target location 834 (assuming that
robot 860 leaves
before robot 862), the robot at queue location 850 will proceed to target
location 834 to be
serviced by station 840.
In yet another embodiment, there is shown in Fig. 13 the shared queue 830 of
Fig.
12 divided into a split queue having queue groups 830a and 830b. This shared
queue will
operate in the same manner as the shared queue 830 of Fig. 12; however, it is
split into two
queue groups due to the proximity of path 870, which is traversed by operators
and robots,
such as robot 872. The first queue group 830a has queue locations 850-855 on
one side of
path 870 and a second queue group 830b has queue locations 856-858 on the
opposite side
of path 870. The queue locations in the two queue groups 830a and 830b, even
though
physically separated, together form a single queue for target locations 832,
834, and 836.
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While the foregoing description of the invention enables one of ordinary skill
to make
and use what is considered presently to be the best mode thereof, those of
ordinary skill
will understand and appreciate the existence of variations, combinations, and
equivalents
of the specific embodiments and examples herein. The above-described
embodiments of
the present invention are intended to be examples only. Alterations,
modifications and
variations may be effected to the particular embodiments by those of skill in
the art without
departing from the scope of the invention, which is defined solely by the
claims appended
hereto. The invention is therefore not limited by the above described
embodiments and
examples, embodiments, and.
Having described the invention, and a preferred embodiment thereof, what is
claimed
as new and secured by letters patent is:
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