Abstract:
A method for performing tasks on items located in a space using a robot, the items being located proximate fiducial markers, each fiducial marker having a fiducial identification. The method includes receiving an order to perform a task on at least one item and determining the fiducial identification associated with the at least one item. The method also includes obtaining, using the fiducial identification of the at least one item, a set of coordinates representing a position of the fiducial marker with the determined fiducial identification, in a coordinate system defined by the space. The method further includes navigating the robot to the coordinates of the fiducial marker associated with said determined fiducial identification.

Description:
RELATED APPLICATIONS 
     This application is related to U.S. patent application Ser. No. 14/815,110, titled “Operator Identification and Performance Tracking”, filed concurrently with this application, incorporated herein by reference. 
     FIELD OF INVENTION 
     This invention relates to robotic navigation using semantic mapping and more particularly to robotic navigation using semantic mapping to navigate robots throughout a warehouse in robot-assisted product order-fulfillment systems. 
     BACKGROUND 
     Ordering products over the internet 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 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. 
     Robot assisted order-fulfillment systems have been used to increase efficiency and productivity. However, there is still a need to further increase efficiency in such systems. 
     SUMMARY 
     In one aspect, the invention features a method for performing tasks on items located in a space using a robot, the items being located proximate fiducial markers, each fiducial marker having a fiducial identification. The method comprises receiving an order to perform a task on at least one item and determining the fiducial identification associated with the at least one item. The method also includes obtaining, using the fiducial identification of the at least one item, a set of coordinates representing a position of the fiducial marker with the determined fiducial identification, in a coordinate system defined by the space, The method further includes navigating the robot to the coordinates of the fiducial marker associated with said determined fiducial identification. 
     In other aspects of the invention one or more of the following features may be included. The method may further include communicating with a human operator to perform the task on the at least one item, wherein the task includes one of retrieving the at least one item and placing it on the robot or removing the at least one item from the robot and storing it proximate the fiducial marker. The space may be a warehouse containing a plurality of items stored in a plurality of containers dispersed throughout the warehouse. Each fiducial marker may be associated with and located proximate to one or more of the containers. The step of determining the fiducial identification may include establishing a fiducial identification system based on a physical layout of the containers dispersed throughout the warehouse and associating each container to a fiducial identification corresponding to the physical location of the container in the warehouse. The step of associating each container to a fiducial identification may further include linking the fiducial identification of the container to the items. The step of determining the set of coordinates representing a position of the fiducial marker with the determined fiducial identification may include correlating the determined fiducial identification with its corresponding fiducial marker and retrieving a set of coordinates representing the position of said fiducial marker in the coordinate system of the warehouse. Retrieving the set of coordinates representing the position of said fiducial marker may include determining a pose for the fiducial marker within the warehouse and the step of navigating may include propelling the robot to the pose without using intermediate fiducial markers to guide the robot to the fiducial marker correlated to the determined fiducial identification. The step of navigating may further include using a predetermined map of the warehouse including a pose for each fiducial marker to guide the robot to the fiducial marker. 
     In another aspect of this invention there is a robot configured to perform tasks on items located in a space, the items being located proximate fiducial markers, each fiducial marker having a fiducial identification. The robot includes a processor configured to determine a fiducial identification associated with at least one item on which the robot is to perform a task. The robot is further configured to obtain, using the fiducial identification of the at least one item, a set of coordinates representing a position of the fiducial marker with the determined fiducial identification, in a coordinate system defined by the space. There is a navigation system configured to navigate the robot to the coordinates of the fiducial marker associated with the determined fiducial identification. 
     In other aspects of the invention one or more of the following features may be included. The robot may include an interface device configured to communicate with a human operator to perform the task on the at least one item. The task may include one of retrieving the at least one item and placing it on the robot or removing the at least one item from the robot and storing it proximate the fiducial marker. The space may be a warehouse containing a plurality of items stored in a plurality of containers dispersed throughout the warehouse. Each fiducial marker may be associated with and located proximate to one or more of the containers. Each container in the warehouse may be associated to a fiducial identification corresponding to the physical location of the container in the warehouse. The fiducial identification of the container may be linked to the items stored in the containers. The processor may further be configured to correlate the determined fiducial identification with its corresponding fiducial marker and retrieve a set of coordinates representing the position of said fiducial marker in the coordinate system of the warehouse. The processor may further be configured to determine a pose for the fiducial marker within the warehouse and the navigation system may be configured to propel the robot to the pose without using intermediate fiducial markers to guide the robot to the fiducial marker correlated to the determined fiducial identification. The navigation system may include a map of the warehouse with a pose for each fiducial marker. 
     These and other features of the invention will be apparent from the following detailed description and the accompanying figures, in which: 
    
    
     
       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; 
         FIG. 6  is a table of the fiducial identification to pose mapping; 
         FIG. 7  is a table of the bin location to fiducial identification mapping; and 
         FIG. 8  is a flow chart depicting product SKU to pose mapping process; and 
     
    
    
     DETAILED DESCRIPTION 
     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 . 
     A typical 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 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&#39;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 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 could also be utilized with other standard tasks associated with such a warehouse system, such as, consolidation of items, counting of items, verification, and inspection. 
     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  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. In addition, certain robots and operators may be performing a placing or storage task to stock the warehouse with items or other tasks such as consolidation of items, counting of items, verification, and inspection. 
     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 determined. To do this, one of the robots  18  navigates the warehouse and builds a map  10   a ,  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  10   a  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  10   a  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&#39;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, ω) 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 image and in step  204  searches for fiducial markers within the captured images. In step  206 , if a fiducial marker is found in the image (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, ω). 
     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.  402   a - f ) within warehouse  10 , which are correlated to particular fiducial ID&#39;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&#39;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&#39;s and from the fiducial ID&#39;s, the pose of each fiducial ID is obtained in step  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&#39;s known, robot  18  can readily navigate to any one of the fiducial ID&#39;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.