Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2002-03-05
2004-04-06
Mullen, Jr., Thomas J (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S539130, C340S691100, C340S691600, C340S692000, C340S870030
Reexamination Certificate
active
06717517
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to an area specific event-driven information system and method used to monitor and track the location of items and relational events within a defined environment. Based on the movement and relation of the items in the environment, the invention performs user-specified actions to provide warnings and/or advice of authorized user defined proximities or to locate the items in the environment through the use of peripheral warning or communication devices.
BACKGROUND
Computer systems and technology employing electromagnetic frequencies, such as radio frequencies, to track the location of an object in an environment are generally known in the art. Many systems track items through area detection tracking. Area detection tracking commonly uses a single computer linked to radio frequency receivers placed periodically throughout a facility. The receivers attempt to locate tag transmitters placed on objects in the facility. The receivers employ a single antenna with a predetermined bandwidth. The larger the bandwidth the larger the potential tracking area to be covered but also the greater amount of energy required to operate the system. When the tag transmitter enters the bandwidth of a receiver, the receiver receives an identification code transmitted by the tag and relays the code to the computer. The computer then records the location of the object bearing the tag transmitter based on the location of the receiver in the facility that relayed the identification code.
Area detection tracking possesses many shortcomings. First, the systems typically provide insufficient coverage to track items to an acceptable resolution. Typically, area detection systems place receivers at stations or sites where objects are expected to be, such as the next station in a manufacturing process. The area detection system in those cases is merely a location verification system. The system reports that an item has arrived at its designated station, has arrived late, or at the incorrect station. However, the system has no ability to locate an item in a facility that has deviated from its designed course. Additionally, location verification systems are easy to intentionally avoid. Because receivers are only placed in particular locations with only a predetermined transmission receiving field, a deviant individual with knowledge of the system or receiver technology could remove items from the facility without detection.
Area detection tracking systems also do not provide any information on the direction in which an item bearing a transmitter has moved once it leaves the area-detection field of a receiver. These systems use point-to-point-tracking schemes. These schemes track the history of the movement of an object as it passes within the radio frequency fields of each receiver but cannot determine the direction of movement of an item. In such cases, the area detection systems provide information on the last recorded location of an object but provide no information on the object's current location until the object passes within the radio frequency field of another receiver. In large facilities, such as manufacturing plants, office buildings, warehouses and hospitals, many paths of movement could branch from each area detection point making it difficult, if not impossible, to know the current location of an item when the item is not within the radio frequency area of a receiver.
In an attempt to overcome the shortcomings attributable to area detection systems, arrays of receivers are distributed in a grid pattern with the size of an detection area determined by the predetermined spacing of receivers based on the width of its radio frequency field. In a grid area detection scheme, radio frequency coverage of facility is increased closing the space between receivers thereby providing increased data collection and higher resolution for point-to-point tracking—the more receivers, the closer together, the greater the ability to plot the movement of the object throughout the facility.
Grid area detection systems carry serious disadvantages. First, grid systems are typically only used in smaller facilities with open floor plans such in manufacturing facilities for semiconductors, high-priced electronics or medical equipment. The grid area detection systems require many receivers in close proximity that make the capital and installation of such a system cost prohibitive in large facilities or in facilities with many corridors, rooms, multiple floors, and numerous points of ingress and egress. Second, grid detection systems are expensive to operate in terms of energy costs to run the numerous receivers. To minimize the operational costs of continuously running all receivers and transmitters, motion detection devices and circuits are employed in the facility to activate receivers only when objects are in motion in close proximity. However, the addition of motion detection technology to the system complicates operation of the detection efforts and adds additional installation and capital costs as well as complexities to the programming required to operate the system.
To overcome the disadvantages of the area detection methods, more complex tracking systems such as time-of-arrival and signal-strength methods have been developed to pinpoint and continuously track the location of an object within a facility. In such programs, receivers are placed strategically throughout a facility. As an object moves through a facility, the exact location of an object is determined by a time-of-arrival determination based on the amount of time it takes multiple receivers to receive a transmission from an item tagged with a transmitter. Based on the timing receipt of the signal from the multiple receivers, the computer can determine the location of items by correlating the time differential of signal receipt as a distance of the object from each receiver. Likewise, a signal-strength method determines the location of an object from the strength of its transmission received by multiple receivers. Here, signal-strength directly correlates with the distance of the object from the receiver, with the transmission signal being stronger the closer it is to a receiver.
The time-of-arrival and signal-strength methods also have disadvantages. Although these systems can determine the exact location of an object, they can only do so if the transmission from an object falls within the radio frequency area of at least three receivers. Accordingly, many receivers must be placed throughout a facility to provide sufficient coverage. Additionally, the tag transmitter assigned to an object often must transmit through walls, machinery and other obstructions that may absorb the transmission from the transmitter of the object introducing unpredictable levels of attenuation of signal strength or time delay in the receivers' receipt of the signal. Obstructions may also deflect or reflect the signal of the transmitter projecting a false or ghost signal that does not correspond with the true location of the object. The time-of-arrival and signal-strength methods of tracking also involve complex transmitter and receiver circuitry and computer algorithms to determine the location of an item from the signal receipt by multiple receivers adding to the cost of the system and operational complexities. Because of these constraints, such systems typically are employed in small manufacturing facilities and offices where valuable items are often transported throughout the facility requiring continuous and detailed information on the items whereabouts.
Prior art radio frequency locating systems use single-frequency technology in locating systems. A limited number of other radio frequency locating systems use spread-spectrum radio communications in the high megahertz frequency ranges. Operation in the high frequency ranges is required to provide a larger bandwidth to increase the area of detection and the strength of the detection field over the area. Because of operation at these high frequencies, Federal Communic
Howard & Howard
Mullen, Jr. Thomas J
USM Systems, Ltd.
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