# Patent

## Title
Wireless tracking system and method with tag removal detection

## Abstract

A wireless tracking system and method with a tag removal detection feature is disclosed herein. The system and method utilize a tag attached to an asset which includes a processor, a motion sensor (such as an accelerometer), a transceiver, a tag removal sensor and a power source having a limited supply of power. The tag removal sensor is a closed circuit device which is activated only when the motion sensor detects motion. In this manner, the tag conserves power since the tag is typically only in motion ten percent of the day. If the tag is removed from the asset, the closed circuit is opened, which confirms the removal of the tag from the asset, and an alert is activated by the system.

## Background
CROSS REFERENCES TO RELATED APPLICATIONS
The Present Application claims priority to U.S. Provisional Patent Application No. 60/981,459, filed on Oct. 19, 2007.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to wireless tracking systems and methods. More specifically, the present invention relates to a system and method for determining if a tracking tag has been removed from an asset.
2. Description of the Related Art
The ability to quickly determine the location of objects located within a facility is becoming a necessity of life. To the uninformed observer, the placement of transponders, also known as tags, on numerous non-stationary objects whether in an office or home would appear to be an unnecessary use of resources. However, the uninformed observer fails to appreciate the complexity of modern life and the desire for efficiency, whether at the office or home.
For example, in a typical hospital there are numerous shifts of employees utilizing the same equipment. When a new shift arrives the ability to quickly locate medical equipment not only results in a more efficient use of resources, but also can result in averting a medical emergency. Thus, the tracking of medical equipment in a hospital is becoming a standard practice.
The tracking of objects in other facilities is rapidly becoming a means of achieving greater efficiency. A typical radio frequency identification system includes at least multiple tagged objects, each of which transmits a signal, multiple receivers for receiving the transmissions from the tagged objects, and a processing means for analyzing the transmissions to determine the locations of the tagged objects within a predetermined environment. One exemplary method triangulates the strongest received signals to determine the location of a tagged object. This method is based on the assumption that the receivers with the strongest received signals are the ones located closest to the tagged object. However, such an assumption is sometimes erroneous due to common environmental obstacles. Multipath effects can result in a further located receiver having a stronger signal from a tagged object than a more proximate receiver to the tagged object, which result in a mistaken location determination.
Federman, U.S. Pat. No. 6,137,414, for an Asset Security Tag, discloses a tamper alarm circuit that is closed upon removal of a tracking tag from an asset thereby resulting in an alarm signal being sent to monitors.
Inoue, et al., U.S. Pat. No. 5,570,080, for a Theft Prevent Tab Device having Alarm Mechanism Housed Therein, discloses a tag body that is fastened to merchandise and which emits an audible alarm if improperly removed from the merchandise.
Hanlon, U.S. Patent Publication Number 2007/0139199, for a Method And Apparatus For An Active Radio Frequency Identification Tag, discloses a dual mode active RFID tag which chirps at different rates if in motion or stationary for location tracking of an asset.
Yashina, U.S. Pat. No. 5,068,643, for a Burglarproof Device, discloses a device that includes a vibration sensor and an optical sensor. When the vibration sensor is activated, by vibration, a signal is sent to the optical sensor to determine the level of ambient light from relative brightness to relative darkness. If the ambient level is too dark, an alarm circuit is activated on the device to indicate that the goods to which the device is attached has been placed under or in a thief's clothing.
Trosper, U.S. Pat. No. 7,123,148, for Wireless Communication Devices, Radio Frequency Identification Devices, radio Frequency Identification Device Communication Systems, Wireless Communication Methods, And radio Frequency Identification Device Communication Methods, discloses a RFID device that is capable of receiving a wireless signal for identification within numerous objects in inventory.
Dumont, U.S. Pat. No. 5,587,703, for Universal Merchandise Tag, discloses a merchandise tag which sounds if the tag is cut-away from the merchandise or exits the store.
Watters, et al., U.S. Pat. No. 6,806,808, for a Wireless Event-Recording Device With Identification Codes, discloses a passive transponder that has a sensor for detecting a physical or chemical event or state without using a power source of its own.
Glick, et al., U.S. Pat. No. 7,002,473, for a Loss Prevention Device, discloses placing a RFID tag on an article and periodically interrogating each RFID tag to determine if the tag is still within a predetermined zone.
Pulkkinen, et al, U.S. Pat. No. 6,954,148, for a Method And System For Selectively Monitoring Activities In A Tracking Environment, discloses a system which monitors the activities of patients and caregivers within a hospital.
Clucas, U.S. Pat. No. 7,042,359, for a Method And Apparatus To Detect A Plurality Of Security Tags discloses an electronic article surveillance system which includes a multitude of expensive RFID tags attached to expensive goods and a multitude of inexpensive RFID tags attached to inexpensive goods, and means to distinguish between the types of tags.
Although the prior art has provided numerous solutions to prevent the theft of goods, the prior art has yet to resolve tag removal issues associated with location asset tracking. Further, the prior art has failed to recognize the problems associated with wireless location asset tracking.
BRIEF SUMMARY OF THE INVENTION
The present invention has recognized that tag removal in a wireless location asset tracking system complicates the asset tracking function of the system since additional components must be added to an already power exhausted and space restricted tag. The present invention is able to provide a solution that resolves the space restriction and power consumption issues.
The present invention restricts the activity of the tag removal sensor by only activating the tag removal sensor when the possibility of the tag being removed is very high. This high possibility activation is performed by a motion sensor controlling the activation of the tag removal sensor through a processor. When the motion sensor registers motion, a signal is sent to the processor to activate the tag removal sensor to determine if the tag is still attached to the asset. In this manner, the power supply of the tag is conserved, while the tag removal function is optimized.
One aspect of the present invention is a method for determining if a tracking tag has been removed from an asset within an indoor facility. The method includes tracking a location of an asset bearing a tag. The tag includes a processor, a motion sensor, a transceiver, a tag removal sensor, and a power source having a limited supply of electrical power. The motion of the tag is detected by the motion sensor and communicated to the processor. An activation signal is activated from the processor to the tag removal sensor. The activation signal activates the tag removal sensor from a low power consumption state to an activation state. The method includes determining if the tag is currently attached to the asset. The method includes transmitting an unattached signal from the tag removal sensor to the processor and from the processor to the transceiver to indicate that the tag is currently unattached to the asset. The method includes broadcasting the unattached signal from the transceiver of the tag to a plurality of network sensors positioned within an indoor facility. The method includes transmitting the unattached signal from at least one of the plurality of network sensors to a positioning engine to generate a warning.
Another aspect of the present invention is a tracking and security device comprising a microcontroller, a wireless network interface, a power supply, a motion sensor and a tag removal sensor. The tag also includes a housing for protecting the components of the tag. The tag removal sensor has a resting mode to conserve power consumption and an activation mode to determine if the tag is attached to an object. During the activation mode, the tag removal sensor determines if the tag is attached to the object. The tag removal sensor has means for informing the microcontroller that the tag is attached to the asset. The motion sensor has means for transmitting a signal to the microcontroller when the tag is in motion. The microcontroller activates the tag removal sensor when the motion sensor transmits a motion signal. The wireless network interface transmits a broadcast from the tag using a wireless communication format. The microcontroller has means for transmitting at a motion rate and at a stationary rate. The housing is preferably composed of a hard plastic material.
Another aspect of the present invention is a system for determining if a tracking tag has been removed from an asset within an indoor facility. The system comprises a plurality of sensors, a positioning engine, a plurality of assets with each of the assets having a tag with a tag removal sensor, and a plurality of access points for receiving the signals from the plurality of sensors and transmitting the signals to the positioning engine. Each tag of each of the plurality of assets has means for determining if the tag has been removed from the asset, and means for broadcasting a signal to each of the plurality of sensors. The positioning engine includes means for tracking each asset within the indoor facility and means for warning an operator of the system if a tag is removed from an asset.
Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.



BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is schematic view of a wireless asset tracking system.
FIG. 2 is a multi-floor view of a facility employing a wireless asset tracking system.
FIG. 3 is a floor plan view of a single floor in a facility employing a wireless asset tracking system.
FIG. 4 is a block diagram of a tag.
FIG. 5 is a schematic diagram of a preferred embodiment of a tag attached to an asset.
FIG. 5A is a circuit diagram of a closed circuit with a tag attached to the asset.
FIG. 5B is a schematic diagram of the tag of the preferred embodiment attached to an asset.
FIG. 5C is a circuit diagram of an open circuit with the tag removed from the asset.
FIG. 6 is a schematic diagram of an alternative embodiment of a tag attached to an asset.
FIG. 6A is a circuit diagram of a closed circuit with a tag attached to the asset.
FIG. 6B is a schematic diagram of the tag of the alternative embodiment removed from an asset.
FIG. 6C is a circuit diagram of an open circuit of the alternative embodiment with the tag removed from the asset.
FIG. 7 is a flow chart of a method of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
As shown in FIGS. 1-3, a wireless asset tracking system is generally designated 50. The system 50 is capable of determining real-time location of an asset 100 within an indoor facility 70. The system 50 preferably includes a plurality of sensors 55, a plurality of bridges 56, a plurality of tags 60 and at least one server 65. One example of the components of the system 50 is disclosed in U.S. Pat. No. 7,312,752 for a Wireless Position Location And Tracking System, which is hereby incorporated by reference in its entirety. A more specific example of the sensors 55 is disclosed in U.S. Pat. No. 7,324,824 for a Plug-In Network Appliance, which is hereby incorporated by reference in its entirety. Another example of a system 50 is set forth in U.S. Pat. No. 6,751,455 for a Power-And Bandwidth-Adaptive In-Home Wireless Communications System With Power-Grid-Powered Agents And Battery-Powered Clients, which is hereby incorporated by reference in its entirety.
The system 50 is preferably employed within an indoor facility 70 such as a business office, factory, home, hospital and/or government agency building. The system 50 is utilized to track and locate various assets (objects) positioned throughout the facility 70. The tags 60 preferably continuously transmit signals on a predetermined time cycle, and these signals are received by sensors 55 positioned throughout the facility 70. In a preferred embodiment, the tags 60 transmit a single every five seconds when in motion, and a signal every ten minutes when stationary. The sensors 55 preferably transmit the data to a bridge 56 for transmission to a server 65. If a sensor 55 is unable to transmit to a bridge 56, the sensor 55 may transmit to another sensor 55 in a mesh network-like system for eventual transmission to a bridge 56. In a preferred embodiment, a transmission may be sent from a transmission distance of six sensors 55 from a bridge 56. The server 65 preferably continuously receives transmissions from the sensors 55 via the bridges 56 concerning the movement of assets 100 bearing a tag 60 within the facility 70. The server 65 processes the transmissions from the sensors 55 and calculates a real-time position for each of the assets 100 bearing a tag 60 within the facility 70. The real-time location information for each of the assets 100 bearing a tag 60 is preferably displayed on an image of a floor plan of the indoor facility 70, or if the facility 70 has multiple floors, then on the floor plan images of the floors of the facility 70. The floor plan image may be used with a graphical user interface so that an individual of the facility 70 is able to quickly locate assets 100 within the facility 70.
The assets 100 are preferably items of value to the owners or users of the system 50 and/or the facility 70. In a hospital setting, the assets 100 could include vital sign monitoring devices, kidney dialysis machines, imaging devices, and other like items that are valuable and mobile. In an office setting, the assets 100 could be computers, copiers, printers, and like devices. Those skilled in the pertinent art will recognize that the assets are anything of value to a user and mobile.
As shown in FIG. 1, the system 50 utilizes sensors 55 to monitor and identify the real-time position of non-stationary assets 100 bearing tags 60. The sensors 55a-f preferably wirelessly communicate with each other (shown as double arrow lines) and with a server 65 through a wired connection 66 via at least one bridge 56, such as disclosed in the above-mentioned U.S. Pat. No. 7,324,824 for a Plug-In Network Appliance. The tags 60a-c transmit signals (shown as dashed lines) which are received by the sensors 55a-e, which then transmit signals to bridges 56 for eventual transmission to a server 65. The server 65 is preferably located on-site at the facility 70. However, the system 50 may also include an off-site server 65, not shown.
Each tag 60 preferably transmits a radio frequency signal of approximately 2.48 GigaHertz (“GHz”). The communication format is preferably IEEE Standard 802.15.4. Those skilled in the pertinent art will recognize that the tags 60 may operate at various frequencies without departing from the scope and spirit of the present invention.
As shown in FIGS. 2-3, the facility 70 depicted is a hospital. The facility 70 has a multitude of floors 75a-c. An elevator 80 provides access between the various floors 75a, 75b and 75c. Each floor 75a, 75b and 75c has a multitude of rooms 90a-i, with each room 90 accessible through a door 85. Positioned throughout the facility 70 are sensors 55a-o for obtaining readings from tags 60a-d attached to or integrated into non-stationary assets 100a, 100b (see FIGS. 2 and 4). A bridge 56 is also shown for receiving transmissions from the sensors 55 for processing by the server 65.
As shown in FIG. 4, a tag 60 preferably includes a microcontroller or processor 101, a wireless network interface 103 having an antenna, a power supply 104, a motion sensor 105 and a tag removal sensor 106. The processor 101 is in communication with the tag removal sensor 106, motion sensor 105 and wireless network interface 103. The power supply 104 preferably provides power to the processor 101, the motion sensor 104, the tag removal sensor 106 and the wireless network interface 103. The power supply 104 is preferably a battery such as a lithium battery. The power supply 104 is preferably the only source of power for the tag 60. Conserving the energy use of the tag 60 allows the tag 60 to have greater use period before needing to be recharged or replaced. In order to conserve the energy use of the tag 60, it is preferably to activate the motion sensor 105 and the tag removal sensor 106 only when necessary. Preferably the components of the tag are enclosed within a housing indicated by the dashed line.
In a preferred embodiment, as shown in FIGS. 5, 5A, 5B and 5C, the tag removal sensor 106 is a circuit 120 including a conductive tape 125 which is attached to a surface of the asset 100 and two conductive metal pins 130 with external contacts 135 which are placed in contact with the conductive tape 125. As long as the external contacts 135 of the conductive metal pins are in contact with the conductive tape, the circuit 120 is closed. The circuit 120 operates in a resting mode and an activation mode. In the activation mode, a current flows through the circuit 120. In the resting mode, the circuit 120 does not receive a current. The activation mode is activated by the detection of motion by the motion sensor 105. If the circuit 120 is in the activation mode and the circuit is open, due to the removal of the tag from the asset, which would remove the external contacts 135 of the conductive metal pins 130 from the conductive tape 125, then an alarm signal is transmitted from the tag removal sensor 106 to the processor 101 for broadcasting through the wireless interface to the plurality of network monitors 55.
In an alternative embodiment, as shown in FIG. 6, the tag removal sensor 106 comprises a spring loaded switch 155 which is depressed against a surface of the asset 100. As long as the switch 155 is depressed, a circuit 120′ is closed. The tag removal sensor 106 operates in a resting mode and an activation mode. In the activation mode, a current flows through the circuit 120′. In the resting mode, the circuit 155 does not receive a current. The activation mode is activated by the detection of motion by the motion sensor 105. If the circuit 155 is in the activation mode and the circuit is open, due to the removal of the tag from the asset, which would activate switch, then an alarm signal is transmitted from the tag removal sensor 106 to the processor 101 for broadcasting through the wireless interface to the plurality of network monitors 55.
Reducing the power consumption of the tag 60 is an important aspect of the present invention. Typically, an asset 100 bearing a tag 60 is in motion ten percent of the day. The tag removal sensor 106 is only in its activation mode when the tag 60 is in motion as indicated by the motion sensor 105. Thus, ninety percent of the day, the tag removal sensor 106 is in a resting mode and using little or no energy from the power supply 104. When the tag 60 is in motion, the tag removal sensor 106 is preferably queried every five seconds by the processor 101 concerning the attachment of the tag 60 to the asset 100. When the tag 60 is stationary, the tag removal sensor 106 is in its resting mode and not queried by the processor 101. By operating in this manner, the power efficiency of the tag 60 is ten times greater than constantly querying the tag removal sensor 106 throughout the day concerning the attachment status of the tag 60. However, the tag 60 is still able to provide continuous security monitoring since the motion sensor 105 transmits a motion signal when motion of the tag 60 is detected thereby resulting in an activation signal transmitted from the processor 101 to the tag removal sensor 106.
A method 200 of the present invention is illustrated in FIG. 7. At block 202, the tracking of a location of an asset 100 bearing a tag 60 is performed by the sensors 55 of the system 50 which receive readings from each tag 60. For location tracking, a sensor 55 receives a signal which includes reading inputs from a tag 60. The reading inputs from the tag 60 preferably include the tag identification, the signal strength, the link quality and the time of the reading, all of which are inputted as a single sensor reading. In this manner, the system is able to track the location of the asset 100 bearing the tag 60. At block 204, motion is detected by the motion sensor 105 of the tag 60, which transmits a signal to the processor 101. The motion could be the asset 100 being moved from one location to another, or the motion could be the removal of the tag 60 from the asset 100. At block 206, an activation signal is transmitted from the processor 101 to the tag removal sensor 106. The activation signal activates the tag removal sensor 106 from a low power or resting mode to a high power or activation mode. In this manner, the limited power supply 104 of the tag 60 is not quickly exhausted by having the tag removal sensor 106 in a constant high power activation mode. At decision 208, a determination is made concerning the attachment status of the tag 60. This determination is performed by the tag removal sensor 106. If the tag removal sensor 106 determines that it is still attached to the asset, then at block 210, a signal is sent that the tag 60 is attached to the asset 100, and the tag 60 continues to broadcast location readings to the sensors 55. If the tag removal sensor 106 determines that it is not attached to the asset, then at block 212, a signal is sent from the tag removal sensor 106 to the processor 101 that the tag 60 has been removed from the asset 100. At block 214, the processor 101 transmits an unattached signal through the wireless network interface 103, which at block 216 is broadcast to the plurality of network sensors 55 of the system 50. At block 218, at least one of the plurality of network sensors 55 transmits the unattached signal to the positioning engine 65 which generates an alert warning to the users of the system 50 informing the users that a tag 60 has been removed from an asset 100.
In the above-described manner, the tag 60 can operate longer on its limited power supply 104 while providing an optimized tag removal security function.
From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes modification and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claim. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.

## Claims

1. A method for determining if a tracking tag has been removed from an asset, the method comprising:
tracking a location of an asset bearing a tag comprising a motion sensor;
detecting motion of the tag by the motion sensor;
transmitting an activation signal to a tag removal sensor disposed on the tag, the activation signal activating the tag removal sensor from a low power consumption state to an activation state;
determining if the tag is currently attached to the asset;
transmitting an unattached signal to a transceiver of the tracking tag to indicate that the tracking tag is currently unattached to the asset;
broadcasting the unattached signal to a plurality of network sensors positioned within an indoor facility; and
transmitting the unattached signal from at least one of the plurality of network sensors to a positioning engine to generate a warning to an operator.

2. The method according to claim 1 wherein the tag removal sensor is in communication with a processor of the tracking tag, and the processor is in communication with the motion sensor and the transceiver.

3. The method according to claim 1 wherein the tag removal sensor is a plurality of metal pins and a strip of conductive tape, each of the plurality of metal pins comprising a body with an external contact, each of the plurality of metal pins is secured to the asset with the strip of conductive tape thereby creating a closed circuit, wherein removal of the tracking tag from the asset opens the circuit which generates an unattached signal.

4. The method according to claim 1 wherein the tag removal sensor is a spring loaded switch, wherein removal of the tracking tag from the asset activates the switch which generates an unattached signal.

5. The method according to claim 1 wherein the warning is a display on a graphical user interface.

6. The method according to claim 1 wherein the warning is an email message to at least one operator.

7. The method according to claim 1 wherein the warning is a SMS to at least one operator.

8. The method according to claim 1 wherein the tracking tag further comprises a power source having a limit supply of electrical power.

9. The method according to claim 1 wherein the tracking tag transmits a radiofrequency transmission of approximately 2.48 GigaHertz, and each of the plurality of network sensors communicates utilizing a 802.15.4 protocol.

10. A system for determining if a tracking tag has been removed from an asset, the system comprising:
a plurality of network sensors, each of the plurality of network sensors positioned within an indoor facility;
a tracking tag attached to an asset, the tracking tag comprising
means for detecting motion of the tracking tag,
a tag removal sensor activated from a low power consumption state to an activation state upon a signal from the motion detecting means,
means for wirelessly transmitting to each of the plurality of network sensors a signal that the tracking tag has been removed from the asset; and

means for processing the signals from the tracking tag.

11. The system according to claim 10 wherein the processing means is a remote server in communication with the plurality of network sensors.

12. The system according to claim 10 wherein the tag removal sensor is a plurality of metal pins and a strip of conductive tape, each of the plurality of metal pins comprising a body with an external contact, each of the plurality of metal pins is secured to the asset with the strip of conductive tape thereby creating a closed circuit, wherein removal of the tracking tag from the asset opens the circuit which generates an unattached signal.

13. The system according to claim 10 wherein the tag removal sensor is a spring loaded switch, wherein removal of the tracking tag from the asset activates the switch which generates an unattached signal.

14. The system according to claim 10 wherein the tracking tag wirelessly transmits a radiofrequency transmission of approximately 2.48 GigaHertz, and each of the plurality of network sensors communicates utilizing a 802.15.4 protocol.

15. A system for tracking and securing a plurality of assets within an indoor facility, the system comprising:
a plurality of movable assets, each of the plurality of movable assets having a tracking tag, the tracking tag comprising a processor, a motion sensor, a tag removal sensor, a limited power supply and a transceiver, the tracking tag transmitting a signal at a first rate in a stationary mode and at a second rate in a motion mode, the tag removal sensor activated from a low power resting mode to an activation mode during the motion mode, the tracking tag transmitting an alarm signal if the tracking tag is removed from the asset;
a plurality of network monitors positioned throughout the indoor facility, each of the plurality of network monitors receiving a plurality of tracking tag transmissions from each of the tracking tags of each of the plurality of assets, and transmitting the plurality of tracking transmissions;
a plurality of access points for receiving the plurality of tracking transmissions from the plurality of network monitors and for transmitting the plurality of tracking tag transmissions; and
a position location engine comprising means for receiving the plurality of tracking tag transmissions from the plurality of access points and for determining the real-time location of each of the movable assets within the indoor facility, and means for alerting an operator of the system if a tag is removed from an asset.

16. The system according to claim 15 wherein the tag removal sensor is a plurality of metal pins and a strip of conductive tape, each of the plurality of metal pins comprising a body with an external contact, each of the plurality of metal pins is secured to the asset with the strip of conductive tape thereby creating a closed circuit, wherein removal of the tracking tag from the asset opens the circuit which generates an unattached signal.

17. The system according to claim 15 wherein the tag removal sensor is a spring loaded switch, wherein removal of the tracking tag from the asset activates the switch which generates an unattached signal.

18. The system according to claim 15 wherein the tracking tag wirelessly transmits a radiofrequency transmission of approximately 2.48 GigaHertz, and each of the plurality of network sensors communicates utilizing a 802.15.4 protocol.

19. The system according to claim 15 wherein the position location engine is located remotely from the indoor facility.

20. The system according to claim 15 wherein the alerting means is selected from the group of warning is a display on a graphical user interface, an email message to at least one operator, a SMS to at least one operator.