Abstract:
A system and method of inventorying multiple objects utilizing a multi-level or a chained radio frequency identification system. The system includes a master tag and a plurality of upper level tags and lower level tags associated with respective objects. The upper and lower level tags communicate with each other and the master tag so that reading of the master tag reveals the presence and absence of upper and lower level tags. In the chained RF system, the upper and lower level tags communicate locally with each other in a manner so that more remote tags that are out of range of some of the upper and lower level tags have their information relayed through adjacent tags to the master tag and thence to a controller.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1 Field of the Invention  
           [0002]    The present invention pertains to electronic inventorying of multiple objects and, more particularly, to a method of inventorying nested and remote objects utilizing a multi-level or chained radio frequency identification tag system.  
           [0003]    2. Description of the Related Art  
           [0004]    Accurate inventorying of bulk articles is vital to many aspects of business and governmental functions. Tracking the shipment and distribution of goods provides verification and accurate accounting, which enables effective management of resources, income, and expenses. It also enables monitoring the whereabouts of goods and equipment, such as military equipment, files containing sensitive information, and the like that are critical to local and national security.  
           [0005]    Bulk articles stored in containers can be difficult to identify and track. Because they are not visible when stored in the container, bulk articles are not available for visual inspection and verification, and changes in their number and condition are not easily monitored. Doing so requires manual labor and breaking of the security of the container, which can result in compromising the condition of the goods and in delay of the shipment and distribution of the goods.  
           [0006]    Bar codes are ineffective in monitoring bulk goods stored in containers because reading of the bar codes requires access to each object or its packaging. While X-ray is possible, it is not available for every type of material. In addition, X-rays do not provide a clear view of each item, and this requires an operator to count each item. Magnetic strips, unlike bar codes, are capable of being read and written to for continual updating. However, like bar codes, they are also not feasible for use with closed containers because, like bar codes, they must be accessible to an electronic strip reader.  
           [0007]    Radio frequency identification (RFID) is another system used for tracking and identifying objects. A key feature of the RFID system is an information-encoded tag that responds to an interrogation signal from an interrogator. Generally, the tag is configured to return the interrogation signal via backscatter reflection. The reflected signal is modulated in accordance with the information stored in the tag.  
           [0008]    As shown in FIG. 1, a basic RFID system  10  includes two components: an interrogator or reader  12  and a transponder (commonly called the RF tag)  14 . The interrogator  12  and RF tag  14  include respective antennas  16 ,  18 . In operation, the interrogator  12  transmits through its antenna  16  a radio frequency interrogation signal  20  to the antenna  18  of the RF tag  14 . In response to receiving the interrogation signal  20 , the RF tag  14  produces a backscatter modulated response signal  22  that is reflected back to the interrogator  12  through the tag antenna  18 . This process is known as modulated backscatter.  
           [0009]    The substantial advantage of RFID systems is the non-contact, non-line-of-sight capability of the technology. The interrogator  12  emits the interrogation signal  20  with a range from 1 inch to 100 feet or more, depending upon the power output and the radio frequency used. Tags can be read through a variety of medium, such as fog, ice, paint, dirt, odors, and other substances, including visually and environmentally challenging conditions where bar codes or other optically read technologies would be useless. RF tags can also be read at remarkable speeds, in most cases responding in less than 100 milliseconds.  
           [0010]    A typical RF tag system  10  will contain a number of RF tags  14  and a single interrogator  12 . The three main categories of RF tags are beam-powered passive tags, battery powered semi-passive tags, and active tags. Each operates in fundamentally different ways.  
           [0011]    The beam-powered RF tag is often referred to as a passive device because it derives the energy needed for its operation from the interrogation signal beamed at it. The tag rectifies the field and changes the reflective characteristics of the tag itself, creating a change in reflectivity that is seen at the interrogator. A battery powered semi-passive RFID tag operates in a similar fashion, modulating its RF cross-section in order to reflect a delta to the interrogator to develop a communication link. Here, the battery is the source of the tag&#39;s operational power. Finally, in the active RF tag, a transmitter is used to create its own radio frequency energy powered by the battery.  
           [0012]    Conventional continuous wave backscatter RF tag systems utilizing passive RF tags require adequate power from the interrogation signal  20  to power the internal circuitry in the RF tag  14  used to amplitude-modulate the response signal  22  back to the interrogator. While this is successful for tags that are located in close proximity to an interrogator, for example, less than three meters, this may be insufficient range for some applications, for example, which require greater than 100 meters.  
           [0013]    There is a need for an RF tag system that can monitor the condition of goods stored in bulk containers and nested within other goods and containers. This need includes the ability to read tags that are out of RF range of the reader.  
         BRIEF SUMMARY OF THE INVENTION  
         [0014]    The disclosed embodiments of the invention are directed to a system and method for identifying and tracking multiple remote objects, particularly objects that are nested within containers, the system and method utilizing a multi-level RFID tag system or a chained RFID tag system.  
           [0015]    In accordance with one embodiment of the invention, a system for tracking a plurality of objects stored in a container is provided. This system includes a plurality of first radio frequency identification tags, each tag configured for attachment to an individual corresponding object in the container; a second RFID tag associated with the container, the second RFID tag configured to communicate with the plurality of first tags and to store information regarding the plurality of first tags.  
           [0016]    In accordance with another aspect of the foregoing embodiment, a remote interrogator is provided that communicates with the second RFID tag to initiate generation of an output signal corresponding to the information stored in the second RFID tag.  
           [0017]    In accordance with another embodiment of the invention, a system for tracking a plurality of objects stored in a container is provided that includes a plurality of RFID tags associated with a corresponding object in the container, each tag configured to communication with other tags and receive and store information from the other tags; and a reader configured to query the plurality of tags and to receive from any one of the plurality of tags the information read from the other plurality of tags.  
           [0018]    In accordance with yet another embodiment of the invention, a communication system and method is provided for remote monitoring of objects, the system and method include a plurality of RFID tags and a reader configured to read the plurality of RFID tags that are within its communication range, each tag configured to read other tags within its communication range to relay information from remote tags to the reader. Ideally, tags within range of the reader can read tags outside the range of the reader and provide to the reader the information from the tags outside of the range of the reader.  
           [0019]    As will be readily appreciated from the foregoing, the system and method of the present invention provides a saving of time in assessing the condition of a plurality of objects in that it avoids reading all of the contents of a container in a serial manner. Rather, in the embodiment utilizing a master tag and a plurality of first tags, the master tag is read only once in order to ascertain the inventory of the container. If the contents change, the system and method of the invention enables rewriting the new updated inventory to the master tag. Alternatively, the embodiment with the plurality of tags allows any one tag to receive all of the information regarding the other tags and to be read quickly and easily, including tags out of range of the reader or interrogator. Thus, a quick inventory can be done by query of the single tag somewhere in the interior or on the exterior of the containment device, such as a room, container, or box. Additionally, inventory of a large group may be done very rapidly in accordance with the method of chained communication wherein tags outside the range of a reader can be set to quickly notify the absence of another tag, and thus the associated object or asset, whereby the entire population is then notified of the change in condition. Thus, an indication of a hazard condition and its location could be quickly chained to a system controller without expensive wiring and overhead. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)  
       [0020]    The foregoing features and advantages of the disclosed embodiments of the present invention will be more readily appreciated as the same become better understood from the following detailed description when taken in conjunction with the accompanying drawings, wherein:  
         [0021]    [0021]FIG. 1 is a schematic representation of a prior art RFID system;  
         [0022]    [0022]FIG. 2 is a schematic representation of a remote inventory system in accordance with a first embodiment of the invention;  
         [0023]    [0023]FIG. 3 is a schematic representation of a second embodiment of the system of the present invention;  
         [0024]    [0024]FIG. 4 is a schematic representation of a system formed in accordance with a third embodiment of the present invention; and  
         [0025]    [0025]FIG. 5 is a schematic representation of a system formed in accordance with a further embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    The system and method of the present invention are directed to electronic monitoring and inventorying of multiple objects, particularly nested and remote objects, utilizing a multi-level or chained radio frequency identification tag configuration.  
         [0027]    In one embodiment of the invention, illustrated in FIG. 2, a system  10  is shown to include a master tag  12  and a plurality of lower level tags  14   a - n.    
         [0028]    Each lower level tag  14   a - n  is preferably a passive radio frequency backscatter tag having a unique memory associated with an object  18   a - n  to which the tag is attached. Because the lower level tag is of a conventional design, such as the radio frequency tag described above with respect to FIG. 1, it will not be described in detail herein. It is to be appreciated that while passive lower level radio frequency tags are preferred for efficiency and economy, semi-active and active tags may also be used.  
         [0029]    Ideally, the lower level tags  14   a - n  are configured to be read only. However, in accordance with another embodiment of the invention, the master tag  12  and lower level tags  14   a - n  may be radio frequency tags of the transmitter, active, or passive backscatter type, as described in more detail hereinbelow.  
         [0030]    The lower level tags  14   a - n  are grouped together in a nest  16  (depicted in dashed lines in FIG. 2) that could be a container, room, box, or having the tags  14   a - n  in a certain area in close proximity to each other. A plurality of objects  18   a - n,  each associated with one of the lower level tags  14   a - n,  are stored together to form the nest  16 .  
         [0031]    The master tag  12  comprises a read-write radio frequency identification tag of conventional design and will not be described in detail herein. Preferably it resides on the container, room, or box in which the objects  18   a - n  are stored. After an initial inventory of the nest  16  is taken, the inventory information is written to the master tag  12 . Subsequent inventories of the contents or subsequent queries of this master tag  12  will now quickly determine the contents of the nest  16 , such as a container, room, box, or area. With this method, time is saved because all of the contents do not have to be read again in a serial manner. Should the contents change, such as one of the objects  18   a - n  being removed from the nest  16 , the master tag  12  can be rewritten with the updated inventory information.  
         [0032]    Referring next to FIG. 3, shown therein is a master tag  20  that contains data related to the contents  22  of a nest  24  of items  26  stored in a room, container, box, or defined area. In this embodiment, no lower level tags are present. Rather, the information regarding the contents of the room, container, or box is held in the memory of the master tag  20 . As the inventory changes, the read-write master tag  20  can be rewritten to reflect the change in the inventory. A quick inventory can now be done by query of the single tag somewhere in the interior on the exterior of the room, container, or box. A reader or interrogator  28  is used to assess the contents of the nest  24  via an interrogation signal  27  that is returned via a backscatter reflection signal  29 .  
         [0033]    Referring next to FIG. 4, shown therein is a further embodiment of the present invention wherein a chained radio frequency identification tag system  30  is depicted to include a master tag  32  and a plurality of upper level tags  34   a - n  associated with objects  35   a - n  and lower level tags  36   a - n  associated with objects  37   a - n.  Each of the upper and lower level tags  34   a - n,    36   a - n  has the ability to be read or to be written to. All of the tags within the given area  38  (shown with dashed lines) are configured to communicate with one another via radio frequency communication in accordance with a preferred embodiment. However, it is not necessary that each of the tags  34   a - n,    36   a - n  be capable of communicating with every other tag within the area  38 . In this embodiment, low range tags can be used, resulting in lower cost and longer battery life components (where such are used).  
         [0034]    Total inventory information can be accumulated, updated, and passed between the upper and lower level tags  34   a - n,    36   a - n,  and to the master tag  32 . Over time, all tags receive and store information relating to all other tag&#39;s identifications, and thus the contents of the entire area  38 . As such, any single tag contains inventory information identical with all other tags within its range. The area of range may be physical, or the area of the tags may be logical, and this may be programmed into the tag. The area may be allowed to be set by physical transmission restraints.  
         [0035]    The system further includes a reader  40  that queries any particular tag within the area  38 . The reader  40  is now given information relating to the entire inventory from any of the lower level or upper level tags  34   a - n,    36   a - n.  In this embodiment, an inventory of a large group may be done very rapidly.  
         [0036]    Additionally, the lower and upper level tags  34   a - n,    36   a - n,  may be set to quickly notify the absence of another tag, and thus an object or asset associated therewith. For example, if a first tag  34   c  had been in communication with a second tag  36   a  for some period of time and then the communication link disappears, it is logical to assume that the second tag  36   a,  and thus its associated asset  39   a,  have been removed. The first tag  34   a  would then send notification to those tags within its range, which tags would in turn do the same. Within a very short period of time, the entire population of lower and upper level tags  34   a - n,    36   a - n  would be notified that an asset had been removed.  
         [0037]    In accordance with another aspect of the foregoing embodiment, any one or all of the lower and upper level tags  34   a - n,    36   a - n  may be configured as read-write tags that are integrated with an alarm or input device  42  that uses the communication link of the associated tag to chain the status of its sensor to higher levels of the system. More particularly, as shown in FIG. 5, the system  44  includes a plurality of read-write tags  46   a - n  that are low range tag and sensor combinations having the ability to communicate with other such tags. The range of each individual tag  46   a - n  is limited, and as such low-cost and long-battery-life components may be used. When the sensor  48  indicates a condition requiring a response, the tag  46   a - n  begins transmission of its condition and its identification. Any other tag within the communication range will receive and repeat this transmission until the message reaches the system controller  50  via the master tag  52 , which is in two-way radio frequency communication with the controller  50 .  
         [0038]    An example of the foregoing might be a tag/sensor used as a fire detection device. Used in this manner, an indication of a hazard condition and its location can be quickly chained to the system controller  50  without expensive wiring and overhead. Such devices are easily placed, and the condition of the sensor could be queried in a similar chained manner. Other examples of use could be tags used as burglar alarms, thermostats, smoke detectors, or lighting controls.  
         [0039]    While preferred embodiments of the invention have been illustrated and described, it is to be understood that various changes may be made therein without departing from the spirit and scope of the invention. Thus, the invention is to be limited only by the scope of the claims that follow and the equivalents thereof.  
         [0040]    All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.  
         [0041]    From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims and the equivalents thereof.