Abstract:
A method and apparatus for monitoring work flow of a resource is disclosed. The method accounts for the expected work flow of the resource in determining the location of the resource as well as dwell times at each work zone.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to systems and methods for monitoring the work flow of a resource. 
         [0003]    2. Description of the Related Art 
         [0004]    Manufacturing costs represent a large portion of the cost to assemble products for eventual sale. However, such manufacturing costs can be greatly reduced by proper work flow management. 
         [0005]    Work flow management, however, typically requires monitoring of the work process itself. Such data not only provides statistical data regarding the assembly process itself (data that can be used to formulate new work flows and processes), it can also provide data that can be used in the assembly process itself. For example, if its known that an assembly has just passed a particular assembly station, that information can be used to begin a process that must be completed before the assembly proceeds to a subsequent assembly station. 
         [0006]    The location of assemblies and parts can be determined using commercially available wireless identification system such as radio frequency identification (RFID) systems. Radio Frequency Identification (RFID) is an automatic identification method that stores and remotely retrieves data using devices called RFID tags or transponders. An RFID tag can be attached to or incorporated into the assembly or part, and can be used to identify the subject using radio waves. Chip-based RFID tags contain silicon chips and antennas. Tags include passive tags, which require no internal power supply, and active tags, which require a power source. 
         [0007]    Active tags work relatively well when they are within the line of sight of three or more location receivers. Problems occur when an active tag is surrounded by metal objects and the radio transmissions travel through indirect paths before they are received. Under these conditions, signal reflect against intermediary objects which may serve as primary signals, and/or multiple signal paths (multipaths) distorting the time of arrival to the receivers. This alteration causes inaccuracies in receiving and time stamping the signals used in the calculation of the location coordinates. 
         [0008]    Commercially available active radio identification systems provide location signals for triangulation ranging between 5 feet to 100 feet from the true location. This level of accuracy is acceptable in the environments where approximation is possible and not critical to a decision process. 
         [0009]    However, in many manufacturing facilities, the accuracy provided by commercially available RFID system may be insufficient due to the close proximity of location boundaries. When the accuracy problem exceeds the assigned location boundary (i.e. aircraft position, work cell, stock room, etc), the reported location is constrained and inaccurate. This not only affects the system&#39;s ability to determine which area the assembly is located, it also affects the gathering of statistics regarding how long the assembly remained in that area. That is because any data regarding how long an assembly was in any particular work cell is typically reset when the assembly leaves the cell. 
         [0010]    The foregoing problems may be ameliorated by increasing the accuracy of the RFID system, but in the multipath environment described above, this can be prohibitively expensive or impossible 
         [0011]    What is needed is a system and method that provides sufficiently accurate and reliable information as to the location status of assemblies, yet does so using commercially available RFID systems. The present invention satisfies that need. 
       SUMMARY 
       [0012]    To address the requirements described above, this document discloses a method and apparatus for monitoring work flow of a resource. In one embodiment, the method comprises the steps of defining a work flow describing an expected work path of the resource, in which the work flow comprising a sequence of a plurality of defined work zones, monitoring the location of a wireless tag associated with a defined resource type and attached to a resource being a member of the defined resource type, when the monitored location of the wireless tag moves from a first work zone to a second work zone, determining if the second work zone sequentially follows the first work zone in the sequence of work zones, if the second work zone does not sequentially follow the first work zone in the sequence of work zones, associating the monitored location of the wireless tag with the first zone, and if the second work zone sequentially follows the first work zone, associating the monitored location of the wireless tag with the second zone. 
         [0013]    One embodiment of the apparatus comprises a wireless locating system having a plurality of tags, a receiver for receiving signals transmitted by the plurality of tags, a locating system for locating the tags based on the received signals, wherein the locating system comprising a processor having a memory storing instructions comprising instructions for performing steps including the steps of accepting a defined a work flow describing an expected work path of the resource, the work flow comprising a sequence of a plurality of defined work zones, monitoring the location a wireless tag associated with a defined resource type and attached to a resource being a member of the defined resource type; when the monitored location of the wireless tag moves from a first work zone to a second work zone, determining if the second work zone sequentially follows the first work zone in the sequence of work zones, associating the monitored location of the wireless tag with the first zone if the second work zone does not sequentially follow the first work zone in the sequence of work zones, and associating the monitored location of the wireless tag with the second zone if the second work zone sequentially follows the first work zone. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
           [0015]      FIG. 1  is an illustration of a wireless locating system such as an RFID system; 
           [0016]      FIG. 2  is a flow chart illustrating exemplary method steps that can be used to set up an improved RFID system; 
           [0017]      FIG. 3  is a flow chart illustrating one embodiment of how the time that each resource spends in each work zone can be monitored; 
           [0018]      FIG. 4  is a flow chart illustrating another embodiment of how work flow can be monitored and the time each resource spends in each work zone can be monitored; and 
           [0019]      FIG. 5  illustrates an exemplary computer system that could be used to implement the processor. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure. 
         [0021]      FIG. 1  is an illustration of a wireless locating system (WLS) such as an RFID system  100 . The RFID system  100  comprises a transmitter  102 , and a plurality of receivers  104 A- 104 C, communicatively coupled to a processor  104 . The processor  104  controls the transmitter  102  to broadcast a signal that is received by transponders or tags  162  that are attached to a product or resource  160  to be assembled. The tag  162  may be an active tag (self powered) or a passive tag (which is powered by energy received from the transmitter  102 ). The tag  162  receives the signal, and responds by transmitting a transponding signal that includes information identifying the tag  162 . The transponding signal is received by the plurality of receivers  104 A- 104 C, and the received signal is provided to the processor  104 . The processor uses the information in the received signals to identify the tag  162  and to determine the location of the tag  162 . Typically, this is accomplished by triangulation using the time-of-arrival of the transponded signal to each of the plurality of receivers  104 A- 104 C. 
         [0022]    In order that the tag  102  provides information regarding the location of the product  160 , a plurality of work zones  152 A- 152 J (hereinafter collectively referred to as work zone(s)  152 ) are defined. Typically, the work zone(s)  152  are defined by providing inputs defining the boundaries of the work zone(s)  152  to the processor  104 , which typically comprises a computer system such as the one further described below. 
         [0023]    The product is assembled by passing through a work path  170 , which can be defined by a sequence of work zones  152 . In the illustrated embodiment, the product  160  is assembled by performing an operation in first work zone  152 A, then by performing another operation in second work zone  152 B, and the subsequently by performing other operations in work zones  152 C,  152 B,  152 D,  152 E, and  152 F, in that order. 
         [0024]    The location of the product  160  can be determined using the tag  162 , and the RFID system  100 . This information can be used to implement “just in time” assembly or to collect data regarding how long the product remains in each work zone  152  or group of work zones  152 . This information can be used to improve production procedures, to modify the work path  170 , or to determine how such modifications might affect time required to assemble the product  160 . 
         [0025]    Unfortunately, as described above, workspace factors such as multipath distortion can negatively affect the accuracy of commercially available RFID systems  100  to the point that the uncertainty in the location of the tag  162  is sufficient to make it difficult for the RFID system  100  to determine which work zone  152  the product is located. For example, when the tag  162  is disposed at position “A,” it is within the first work zone  152 A (F18 Station 001, Splice), but the accuracy of the RFID system  100  in determining the position of the tag  162  is such that the measured location of the tag  162  may place it outside of the work zone  152 A as shown. As a consequence, the estimate of the time that the product  160  spends in the first work station  152 A will be in error. Making matters worse, many commercially available RFID systems  100  reset timers when it believes that the tag  162  has left the work zone  152 A, resulting in very large errors in the elapsed time estimates. 
         [0026]    In the embodiment illustrated in  FIG. 1 , the product leaves the first work zone  152 A and is temporarily placed in the aisle at location “B.” In this location, the RFID location errors are such that the tag  162  is not located to be in any of the other identified work zones  152 . However, when the product  160  is later moved to location “C”, the accuracy is such that the RFID system  1000  may locate the tag  162  and associated product  160  in work zone  152 I instead of the aisle, where the product  160  and tag  162  are actually located. This may cause the RFID system  100  to erroneously begin counting time in work zone  152 I, even if the product is never supposed to enter this work zone  152 I. Similarly, when the product is disposed at location “E,” the RFID system  100  may locate the product  160  and associated tag  162  in work zone  152 C, when in fact, the product is still in the aisle. Not until the product and associated tag  162  is moved to location “F” will the RFID system  100  locate the tag  162  in the proper work zone  152 B (and even then, just as was the case when the tag  162  was in the first work zone  152 A, the accuracy of the RFID system  100  is such that the tag  162  may also be located outside the work zone  152 B when it is, in fact, within the work zone  152 B. This disclosure presents a description of a system and method that ameliorates the foregoing problems. 
         [0027]      FIG. 2  is a flow chart illustrating exemplary method steps that can be used to set up an improved RFID system  100 . As shown in step  202 , resource types are defined, producing resource types  202 D. An example of such resource types is shown in Table I below: 
         [0000]    
       
         
               
               
             
           
               
                 TABLE I 
               
               
                   
               
               
                 Resource Type (R/T) 
                 Resource 
               
               
                   
               
             
             
               
                 1001 
                 F18 
               
               
                 1002 
                 F18 MLG 
               
               
                 1003 
                 F18 NLG 
               
               
                 2001 
                 F18 N/G Tool 
               
               
                   
               
             
          
         
       
     
         [0028]    Each resource (for example, an F18 fighter) is a member of its associated resource type. For example, the F18 is a member of resource type 1001. Next, work zone  152  groups can be defined, as shown in step  204 . Work zone groups are groups that comprise a plurality of defined work zones. The result is work zone group data  204 D. Exemplary work zone groups are shown in Table II below: 
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE II 
               
               
                   
               
               
                 Work Zone Group 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 B67 Final Assembly 
               
               
                   
                 B67 F18 Forward Fuselage 
               
               
                   
                 B67 F18 Inner Wing 
               
               
                   
                 B67 F18 Outer Wing 
               
               
                   
                 B101 Tube Shop 
               
               
                   
                   
               
             
          
         
       
     
         [0029]    In step  206 , work zones  152  are defined. Work zones are boundaried areas where one or more activities related to the assembly of the product  160  take place. They may be defined by specifying the boundaries and giving the work zone  152  a name. Defined work zones  152  are optionally associated with a work group. The result is the work zone data  206 D shown in  FIG. 2 . Exemplary work zone groups are shown in Table III below: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE III 
               
               
                   
                   
               
               
                   
                 Work Zone 
                 Work Group 
               
               
                   
                   
               
             
             
               
                   
                 F18 Station 001 - Splice 
                 B67 Final Assembly 
               
               
                   
                 F18 Station 002 - Installations 
                 B67 Final Assembly 
               
               
                   
                 F18 Station 003 - Operations 
                 B67 Final Assembly 
               
               
                   
                 F18 Station 004 - Pre-Ramp 
                 B67 Final Assembly 
               
               
                   
                   
               
             
          
         
       
     
         [0030]    As described above, each tag  162  is associated with an identifier, and the tags  162  transmit that identifier after they receive a ping from the RFID transmitter  102 . In step  208 , an the identifier of each tag  162  (which is later placed in or on the resources  160 ) is associated with a resource type, thus creating data  208 D relating the tag ID to the resource type. Exemplary data is shown below in Table IV: 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE IV 
               
               
                   
                   
               
               
                   
                   
                   
                 Resource ID 
               
               
                   
                 Tag ID 
                 Resource Type (R/T) 
                 (R/ID) 
               
               
                   
                   
               
             
             
               
                   
                 18042793 
                 F18 
                 AC-E127 
               
               
                   
                 18035132 
                 F15 
                 AC-K13 
               
               
                   
                 18048254 
                 T45 
                 AC-A191 
               
               
                   
                   
               
             
          
         
       
     
         [0031]    One or more work paths  170  are defined, as shown in step  210 . The result is work path data  210 D comprising a list of defined work paths  170 . Exemplary data is shown below in Table V: 
         [0000]    
       
         
               
               
             
           
               
                   
                 TABLE V 
               
               
                   
                   
               
             
             
               
                   
                 F15 Final Assembly 
               
               
                   
                 F18 Final Assembly 
               
               
                   
                 F18 Forward Fuselage 
               
               
                   
                 F18 Inner Wing 
               
               
                   
                 F18 Outer Wing 
               
               
                   
                 T45 Final Assembly 
               
               
                   
                   
               
             
          
         
       
     
         [0032]    The defined work path names are associated with the resource type, as shown in step  212 . The result is data  212 D associating the work path name to the resource type. Exemplary data is shown below in Table VI 
         [0000]    
       
         
               
               
             
           
               
                   
                 TABLE VI 
               
               
                   
                   
               
             
             
               
                   
                 F15 = F15 Final Assembly 
               
               
                   
                 F18 = F18 Final Assembly 
               
               
                   
                 T45 = T45 Final Assembly 
               
               
                   
                   
               
             
          
         
       
     
         [0033]    Work zone paths are then defined, as shown in block  214 . Each work zone path is the work path defined by a sequential listing of the work zones  152  that the resource  160  passes through. The result is work path zone data  214 D. Exemplary data is shown below in Table VII: 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE VII 
               
               
                   
               
               
                 # 
                 R/T 
                 Path Name 
                 Zone Path 
                 Zone Path Group 
               
               
                   
               
             
             
               
                 1 
                 F15 
                 F15 Final Assembly 
                 F15 Station 001 
                 Final Assembly 
               
               
                 2 
                 F15 
                 F15 Final Assembly 
                 F15 Station 002 
                 Final Assembly 
               
               
                 3 
                 F15 
                 F15 Final Assembly 
                 F15 Station 003 
                 Final Assembly 
               
               
                 1 
                 F18 
                 F18 Final Assembly 
                 F18 Station 001 
                 Final Assembly 
               
               
                 2 
                 F18 
                 F18 Final Assembly 
                 F18 Station 002 
                 Final Assembly 
               
               
                 3 
                 F18 
                 F18 Final Assembly 
                 F18 Station 003 
                 Final Assembly 
               
               
                 4 
                 F18 
                 F18 Final Assembly 
                 F18 Station 004 
                 Final Assembly 
               
               
                 1 
                 T45 
                 T45 Final Assembly 
                 T45 Station 001 
                 Final Assembly 
               
               
                   
               
             
          
         
       
     
         [0034]    At the conclusion, the set up process is complete. 
         [0035]      FIG. 3  is a flow chart illustrating one embodiment of how the time that each resource  160  or resource type spends in each work zone  152  can be monitored. A work flow describing an expected work path  170  of the resource is defined. As described above, the work flow comprises a sequence (e.g.  152 A,  152 B,  152 C,  152 B,  152 D,  152 E, and  152 F) of a plurality of the defined work zones  152 . As the resource  160  follows the work path  170 , the RFID system  100  monitors the location of the wireless tag  162  attached to the resource  160  and associated with the defined resource type. 
         [0036]    When the RFID system  100  monitoring the wireless tag  162  determines that the tag  162  has left the work zone  152  in which it was previously located, a zone change event is identified  301 . When this occurs, the RFID system  100  sets a departure time in the previous work zone  152  (the work zone  152  that the tag  162  just exited) for the resource ID associated with the resource  160  to which the tag  162  is attached, as shown in step  302 . Because the resource  160  is no longer in that work zone  152 , the RFID system  100  also resets the zone arrival time for the same zone  152 , as shown in step  304 . The RFID system  100  also updates the zone group dwell time (the amount of time that the tagged resource has spent in the group of work zones  152  that define the work zone group) for the resource ID. Once this is completed, processing for the work zone change event is completed, as shown in  307 . 
         [0037]    For example, referring back to  FIG. 1 , when the RFID system  100  locates the resource  160  outside of the first work zone  152 A, the time at which the resource  160  associated with the resource ID transmitted by the attached tag  162  departed the zone is set (allowing the time the resource  160  dwelled in the work zone  152 A to be computed), and the arrival time for that resource  160  (when it entered the first work zone  152 A) is reset because it is no longer needed and because it will be used to compute the dwell time in the next work zone  152 B in the work zone flow  170 . That is, the arrival time is set when the RFID system  100  locates the tag  162  in another defined workspace). Unfortunately, because of the insufficient accuracy of the RFID system  100 , the arrival time may be set when the tag  162  is physically located at position “C” and not truly disposed in a work zone  152 I. Also, RFID system  100  inaccuracies can cause an zone change event, even when the actual physical location of the tag  162  has not left the zone. For example, the RFID system  100  may locate the tag  162  in an area within area  172 , and out of work zone  152 A. Such errors can cause the accumulated time figures computed above to be substantially in error. 
         [0038]      FIG. 4  is a flow chart illustrating another embodiment of how work flow can be monitored and the time each resource  160  spends in each work zone  152  can be monitored. 
         [0039]    A work flow describing an expected work path  170  of the resource  160  is defined. As described above, the work flow comprises a sequence of a plurality of the defined work zones  152 . As the resource follows the work path, the RFID system  100  monitors the location of the wireless tag  162  attached to the resource  160  and associated with the defined resource type. 
         [0040]    When the monitored location of the wireless tag  162  moves from a first work zone  152  to a second work zone  152 , the RFID system  100  determines whether the second work zone  152  sequentially follows the first work zone  152  in the sequence of work zones  152 . This is shown in step  402 . 
         [0041]    If the second work zone  152  sequentially follows the first work zone  152 , the location of the tag  162  as monitored by the RFID system  100  is associated with the second zone  152  (the RFID system  100  now considers the tag  162  to be in the second zone  152 , and logic passes to step  404 - 408  where appropriate steps are taken to keep track of the time that the resource spends in each work zone  152 , as further detailed below. If not, the location of the tag  162  as monitored by the RFID system  100  remains associated with the first zone  152 . Steps  404 - 408  are bypassed, and logic instead passes to step  410 . Where the time during which the monitored tag is associated with the work zone group to which the first work zone  152  belongs. 
         [0042]    For example, if the monitored location of the wireless tag  162  moves from first work zone  152 A to second work zone  152 B, the RFID system  100  recognizes that the new (second) work zone  152 B is the work zone  152  that should sequentially follow the first work zone  152 A, and hence, considers the tag  162  to be in the second zone  152 B. Hence, the RFID system  100  computes an accumulated time during which the monitored location of the wireless tag is associated with the first zone  152 A. In one embodiment, this can be accomplished by setting a zone departure time for the first zone  152 A to the time at which the monitored location of the wireless tag  162  appeared in the second work zone  152 B, and subtracting the zone arrival time for the first zone  152 A from the zone departure time for the first zone  152 A. This provides the total time that the resource  160  has spent in the first work zone  152 A. 
         [0043]    However, if the monitored location of the wireless tag  162  were instead to move from first work zone  152 A to third work zone  152 C or to any work zone other than second work zone  152 B, the RFID system  100  considers this zone change event to be erroneous, and does not associate the tag  162  with the third work zone  152 . Logic then passes to step  410  to accumulate the work group zone time (since the resource  160  is still within the work group). 
         [0044]    The foregoing operations are shown in additional detail in steps  402 - 410  of  FIG. 4 . First, step  402  determines if new work zone  152  is the next work zone  152  in sequence of work zones  152  that define the work flow for the resource  603  at issue. If the new work zone  152  is the next work zone  152  identified in the sequential list of work zones  152 , step  404  updates the work flow order for the resource ID to indicate that the resource  160  is now located in the new work zone  152 . Step  406  sets the departure time for the previous work zone  152  for that resource ID to the current time (so that the dwell time in that work zone  152  can be computed as a difference between the departure time and the entry time), and step  408  sets the arrival time for the new work zone  152  for that resource ID to the current time. Step  410  computes an accumulated dwell time that the tag is associated with the work flow group (e.g. the accumulated time that the RFID system  100  locates the tag  162  in one at least one of the work zones  152  in the group of work zones. 
         [0045]      FIG. 5  illustrates an exemplary computer system  500  that could be used to implement the processor  104 . The computer  502  comprises a microprocessor  504  and a memory, such as random access memory (RAM)  506 . The computer  502  can be operatively coupled to a display  522 , which presents images such as windows to a user on a graphical user interface  518 B. The computer  502  may be coupled to other devices, such as a keyboard  514 , a mouse device  516 , a printer, etc. Of course, those skilled in the art will recognize that any combination of the above components, or any number of different components, peripherals, and other devices, may be used with the computer  502 . 
         [0046]    Generally, the computer  502  operates under control of an operating system  508  stored in the memory  506 , and interfaces with the user to accept inputs and commands and to present results through a graphical user interface (GUI) module  518 A. Although the GUI module  518 A is depicted as a separate module, the instructions performing the GUI functions can be resident or distributed in the operating system  508 , the computer program  510 , or implemented with special purpose memory and processors. The computer  502  may also implement a compiler  512  which allows an application program  510  written in a programming language such as COBOL, C++, FORTRAN, or other language to be translated into processor  504  readable code. After completion, the application  510  accesses and manipulates data stored in the memory  506  of the computer  502  using the relationships and logic that were generated using the compiler  512 . The computer  502  also optionally comprises an external communication device such as a modem, satellite link, Ethernet card, or other device for communicating with other computers. 
         [0047]    In one embodiment, instructions implementing the operating system  508 , the computer program  510 , and the compiler  512  are tangibly embodied in a computer-readable medium, e.g., data storage device  520 , which could include one or more fixed or removable data storage devices, such as a zip drive, floppy disc drive  524 , hard drive, CD-ROM drive, tape drive, etc. Further, the operating system  508  and the computer program  510  are comprised of instructions which, when read and executed by the computer  502 , causes the computer  502  to perform the steps necessary to implement and/or use the processor  504 . Computer program  510  and/or operating instructions may also be tangibly embodied in memory  106  and/or data communications devices  130 , thereby making a computer program product or article of manufacture. As such, the terms “article of manufacture,” “program storage device” and “computer program product” as used herein are intended to encompass a computer program accessible from any computer readable device or media. 
         [0048]    Those skilled in the art will recognize many modifications may be made to this configuration without departing from the scope of the present disclosure. For example, those skilled in the art will recognize that any combination of the above components, or any number of different components, peripherals, and other devices, may be used. 
       CONCLUSION 
       [0049]    This concludes the description of the preferred embodiments of the present disclosure. The foregoing description of the preferred embodiment has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of rights be limited not by this detailed description, but rather by the claims appended hereto.