Abstract:
A real time location system has a plurality of tag devices. Each tag device has a unique identification code. Each tag device will transmit a location signal when activated. A plurality of location receivers are installed in a fixed location. The location receivers will receive the location signal and calculate a location of the tag device transmitting the location signal. A signal mechanism is coupled to an I/O port of each tag device. The location mechanism provides at least one of an audible signal or visual signal when activated. A location reader is provided. The location reader receives the location data transmitted by the plurality of location receivers to enable a person to locate the tag device transmitting the location signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to a wireless location system, more specifically, to a wireless Real Time Location System (RTLS) which uses audile and/or visible signals to exactly locate a unit being tracked or located (e.g. wireless tag) in an area. 
         [0003]    2. Background of the Invention 
         [0004]    Determining the location of assets, such as equipment, vehicles, inventory, etc., can be important in a variety of different applications. For example, large manufacturing companies typically have warehouses which are used to store parts and inventory. It is important to accurately and timely locate parts and inventory in order to timely and successfully manufacture products. One way to track the location of assets is to use a real time location system. A real time location system will associate each asset, or group of assets, with a tag device. The tag device is capable of communicating with a controller through one or more receivers to provide information used to determine the location of the tag device and thus the location of the associated asset. 
         [0005]    A variety of methods may be used to determine the location of the tag device. One method is by signal strength or Received Signal Strength Indication (RSSI). In this method, the tag device may send a radio frequency signal that is received by one or more antennas that communicate with a controller. Based on the signal, the controller may determine where the tag device is located. This method is generally poor in terms of accuracy and reliability, as the path loss is highly dependent on environmental conditions and affected by fading due to multi path propagation. The accuracy of the RSII method declines rapidly as either the size of the covered area increases, or the size and quantity of metal or other RF reflecting objects and surfaces in and near the covered air space increases. In indoor environments, the reliability of this method is highly dependent on the wall materials and the level of RF signal attenuation between adjacent areas. 
         [0006]    Another method to determine the location of the tag device is to determine a time difference of arrival of a tag device signal. In this method, a tag device will encode a time stamp on a signal that is transmitted. Each controller will report on when the tag device signal is received. While this method does work, it is generally not accurate when the distance between the tag device and the controller is small. The clock devices for each tag device and controller also need to be synchronized in order to provide accurate locations. Furthermore, this method, while giving a general location of the tag device, will not provide an exact location. 
         [0007]    Presently, all current location systems only provide location data and perhaps a display (i.e., map) in order to try and find the item being sought. Thus, the problem with present real time location systems is making the systems sufficiently accurate so that someone with the location data provided by the location system can walk right to the item being sought. 
         [0008]    Therefore, a need exists for a system and method that overcomes the problems associated with the prior art. The system and method will provide a wireless real time location system that is sufficiently accurate so that someone with the location data provided by the location system and the proper tools can walk right to the item being sought. 
       SUMMARY OF THE INVENTION 
       [0009]    A real time location system has a plurality of tag devices. Each tag device has a unique identification code. Each tag device will transmit a location signal when activated. A plurality of location receivers are installed in a fixed location. The location receivers will receive the location signal and calculate a location of the tag device transmitting the location signal. A signal mechanism is coupled to an I/O port of each tag device. The location mechanism provides at least one of an audible signal or visual signal when activated. A location reader is provided. The location reader receives the location data transmitted by the plurality of location receivers to enable a person to locate the tag device transmitting the location signal. 
         [0010]    A method for tracking and locating tag devices comprises: installing a tag device on an asset to be located, the tag device having a unique identification code, the tag device transmitting a location signal when activated; installing location receivers in a proximity of a well defined area housing the asset; activating a desired tag device; receiving the location signal by the location receivers; locating the activated tag device by using the location receivers; and activating a signal mechanism coupled to an I/O port of the tag device, the signal mechanism providing at least one of an audible signal or visual signal when activated. 
         [0011]    The features, functions, and advantages can be achieved independently in various embodiments of the present inventions or may be combined in yet other embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a simplified block diagram of the wireless real time location system of the present invention. 
           [0014]      FIG. 2  is a simplified block diagram of the tag device and handheld mobile reader used in the wireless real time location system of the present invention. 
           [0015]      FIG. 3  is a flowchart depicting a method for a wireless real time location system to accurately locate an item. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Referring to  FIGS. 1 and 2 , a wireless location system  10  is installed in an area defined as Map A. The area Map A may be any type of open or closed area. In the present embodiment, the system  10  will be described in a warehouse setting wherein the system  10  is used to track the location of assets/parts  12 A. However, this should not be seen as to limit the scope of the present invention. The system  10  may be installed in any area where items need to be located. 
         [0017]    The system  10  will install a plurality of tag devices  12 . Each tag device  12  is attached on each asset  12 A, or group of assets that needs to be monitored/located. In the embodiment depicted in  FIG. 1 , five tag devices  12  are shown. However, this should not be seen as to limit the scope of the present invention. The number of tag devices  12  will be dictated by the number of items need to be located. 
         [0018]    As shown in  FIG. 2 , each tag device  12  is an electronic device that containing a microprocessor  14  combined with an antenna  16  housed in a compact package  18 . The packaging  18  is structured to allow each tag device  12  to be attached to the asset  12 A to be tracked/monitored. Each microprocessor  14  of each tag device  12  will be encoded with a unique ID  20 . In order to locate a particular asset, the tag device  12  attached to the specific asset  12 A will be activated. Once the tag device  12  is activated, the tag device  12  will transmit a location signal  15  encoded with the unique ID  20 . 
         [0019]    A plurality of location receivers LR# 1 -LR# 4  is installed in the area defined as Map A. In the embodiment depicted in  FIG. 1 , four location receivers LR# 1 -LR# 4  are shown. However, this should not be seen as to limit the scope of the present invention. The number of location receivers LR# 1 -LR# 4  is generally dictated by the size of the area defined as Map A and the strength and range of each location receivers LR# 1 -LR# 4 . 
         [0020]    The location receivers LR# 1 -LR# 4  are placed in fixed locations in the area defined as Map A. The location receivers LR# 1 -LR# 4  are used to locate the activated tag device  12 . If the activated tag device  12  is in a range of one or more of the location receivers LR# 1 -LR# 4 , the in range location receivers LR# 1 -LR# 4  will receive the encoded location signal  15  sent by the activated tag device  12 . The in range location receivers LR# 1 -LR# 4  will then determine the location of the activated tag device  12 . The location method used to locate the activated tag  12  may be any commonly used wireless location method. 
         [0021]    A handheld mobile location viewer  24  (hereinafter location reader  24 ) that includes an antenna  26  will receive location data signals  17  transmitted by the in range location receivers LR# 1 -LR# 4 . The location reader  24  will direct a person to the asset having the activated tag device  12 . The location reader  24  may further have a monitor  26 . The monitor  26  will give visual data to further help a person locate the asset having the activated tag device  12 . 
         [0022]    Using the location data signals  17  transmitted by the in range location receivers LR# 1 -LR# 4  will allow a person using the location reader  24  to only get in a general vicinity of the asset having the activated tag device  12 . Locations methods such as RSSI, TOA, TDOA generally are only accurate to within 30-60 feet. If the size of the area defined as Map A is a large warehouse, a person would still have to spend a good amount of time to locate the asset having the activated tag device  12 . This is especially true in a warehouse setting where assets may be stacked on top of one another ten to fifteen feet or more in the air. 
         [0023]    For this reason, each tag device  12  will have a signal mechanism  28  coupled to an I/O port  15  of the tag device  12 . The signal mechanism  28  will provide an audible and/or visual signal when activated to further enable the person to locate the asset having the activated tag device  12 . The signal mechanism  28  may be a light device that will illuminate and/or flash when activated and/or an audible device which will transmit an audible signal such as a beeping sound or the like when activated. When illuminated/flashing and/or beeping, the signal mechanism  28  will allow the party to find the exact location of the tag device  12 . 
         [0024]    Once the location receivers LR# 1 -LR# 4  direct a person using the location reader  24  to the general vicinity of the asset having the activated tag device  12 , a user may activate the location mechanism  28  on the activated tag device  12 . In accordance with one embodiment of the present invention, the location reader  24  will have an activation unit  30 . The activation unit  30  is used to activate the location mechanism  28  on the activated tag device  12 . While the tag device  12  may be a passive tag device, in order to provide more reliability and sufficient power for the tag device  12  to power the location reader  24 , the tag device  12  will generally be an active tag device  12  having an internal power supply  32 . 
         [0025]    An excitation unit  34  is generally used to activate a tag device  12  to locate a specific asset. The excitation unit  34  may be a stand alone unit or installed as part of one or more of the location receivers LR# 1 -LR# 4 . Alternatively, the excitation unit  34  may be installed in the location reader  24 . In this embodiment, the location reader  24  will transmit an activation signal of a desired tag  12  in order to locate a specific asset. The antenna  16  of the specific tag device  12  will pick up the activation signal from the location reader  24  and then transmit location signals  15  encoded with the ID number. The location receivers LR# 1 -LR# 4  will use the location signals encoded with the ID number to locate the activated tag device  12 . 
         [0026]    Referring to  FIGS. 1-3 , the operation of the system  10  will be disclosed in further detail. When a specific asset is to be located, the tag device  12  associated with the specific asset is activated. The excitation unit  34  is used to activate the tag device  12  associated with the specific asset. The excitation unit  34  will transmit an activation signal to activate the desired tag  12 . The antenna  16  of the specific tag device  12  will pick up the activation signal from the location reader  24  and then transmit location signals encoded with the ID number. 
         [0027]    The location receivers LR# 1 -LR# 4  may use any type of location method to locate the activated tag  12 . The location receivers LR# 1 -LR# 4  may use RDF, RSSI, TDOA or any other commonly used wireless location methods and combinations thereof. 
         [0028]    The location reader  24  that includes an antenna  26  will receive the location data transmitted by the location receivers LR# 1 -LR# 4 . In accordance with one embodiment of the present invention, the antenna  26  is both an omni and directional antenna. A user will generally set the antenna  26  on the location reader  24  to omni mode for maximum range. In omni mode, the antenna  26  will receive data in all directions. As one gets closer to the specific asset, the user may switch the antenna  26  on the location reader  24  to directional mode. In the directional mode, the location reader  24  will search for the strongest signal in a particular direction. The user will generally move the location reader  24  in different directions looking for the strongest signal. Once the direction of the strongest signal is determined, the user will walk in the direction of the strongest signal while monitoring readings from the location reader  24 . 
         [0029]    The location reader  24  will direct the person to the general vicinity of the asset having the activated tag device  12 . Once in the general vicinity of the asset, the user will activate the location mechanism  28  on the activated tag device  12 . The location mechanism  28  will provide an audible and/or visual signal when activated to enable the person to locate the asset having the activated tag device  12 . 
         [0030]    This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.