Locating a device in a given state

Methods and computer program products for locating devices having a given state by locating a device using an RFID tag associated with the device that responds to queries from an RFID tag reader independently of the state of the device, and determining the state of the device using an RFID tag associated with the device that responds selectively in dependence upon the state of the device. The invention also includes systems for locating devices having a given state. The systems comprise an RFID tag reader for locating a device by reading an RFID tag associated with the device that responds independently of the state of the device, and an RFID tag reader for determining the state of the device by reading an RFID tag associated with the device that responds selectively in dependence upon the state of the device.

RELATED APPLICATIONS

Attention is directed to the commonly assigned, co-pending U.S. patent application by the same inventors, entitled “Network Management Using Suppressible RFID Tags.”

BACKGROUND

The present invention concerns the field of inventory management, and more particularly concerns using RFID tags to locate devices and other assets having a given state.

Radio frequency identification (RFID) tags provide an inexpensive way to manage inventory by enabling the process of locating various devices. Here, locating a device means determining its coordinates or position in a spatially referenced sense, where the term coordinates is used broadly. The coordinates can be, for example, latitude and longitude, distance and direction from a known reference point, proximity to a given intersection such as the intersection of aisles in an office or warehouse, a shelf label location in a warehouse, a room number in an office building, and so forth.

In some situations, an RFID infrastructure can be set up having a number of stationary RFID tag readers located throughout a building or campus, and an edge controller to collate or consolidate information provided by the RFID tag readers. Such a system, which may be called an RFID networked-system application, can locate or track monitored devices that are equipped with RFID tags as the devices move within a geographic area. For example, such a system may be used to locate and track equipment carts in a hospital, forklifts or textbooks in a warehouse, and the like.

Although such RFID networked-system applications are quite effective in locating and tracking devices, they are unable to provide any information concerning the devices beyond their locations. In particular, RFID networked-system applications fail to convey any information regarding the state of the monitored devices. This can be a significant limitation. For example, hospital staff may use such a system to locate the nearest equipment cart, only to find that the nearest cart is presently in use. Likewise, a factory foreman may locate the nearest forklift using such as system, only to find that its battery is discharged.

Thus, there is a need to improve RFID networked-system applications by enabling them to provide state information in addition to locations and trajectories.

SUMMARY

Aspects of the invention include methods and computer program products for locating devices having a given state by locating a device using an RFID tag reader and a first RFID tag associated with the device that responds to queries from an RFID tag reader independently of the state of the device, and determining the state of the device using an RFID tag reader and a second RFID tag associated with the device that responds selectively in dependence upon the state of the device. Another aspect of the invention includes systems for locating devices having a given state. The systems comprise an RFID tag reader for locating a device by reading a first RFID tag associated with the device that responds independently of the state of the device, and an RFID tag reader for determining the state of the device by reading a second RFID tag associated with the device that responds selectively in dependence upon the state of the device.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter, with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. Throughout the drawings, like numbers refer to like elements.

As will be appreciated by one of skill in the art, aspects of the present invention may be embodied as a method, data processing system, or computer program product. Accordingly, aspects of the present invention may take the form of embodiments entirely in hardware, entirely in software, or in a combination of hardware and software referred to as circuits and modules.

Furthermore, aspects of the present invention may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium. Any suitable computer-readable medium may be utilized, including hard disks, CD-ROMs, optical storage devices, magnetic storage devices, and transmission media such as those supporting the Internet or an intranet.

Computer program code for carrying out operations of the present invention may be written in an object oriented programming language such as Java, Smalltalk, or C++. However, the computer program code for carrying out operations of the present invention may also be written in conventional procedural programming languages, such as the C programming language. The program code may execute entirely on a single computer or distributed over a plurality of computers.

The present invention is described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that blocks of the flowchart illustrations and diagrams may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions and/or acts specified in the flowchart and/or block diagram block or blocks.

FIG. 1shows a block diagram of a conventional RFID tag. This diagram is introduced mainly as a descriptive convenience to be used in clearly differentiating the suppressible RFID tag described below with reference toFIG. 2from the conventional RFID tag ofFIG. 1.

As shown inFIG. 1, a conventional RFID tag100comprises a transceiver110, a power converter120, and a tag antenna130. As is well known to those skilled in the art, a conventional passive RFID tag receives electromagnetic energy through the tag antenna130when read or queried by a tag reader. The power converter120, which may be, for example, a rectifier and a simple filter such as a capacitor, transforms the received energy into a form suitable to power the transceiver110, in order that the transceiver110may respond to the tag reader. In contrast to passive RFID tags, active RFID tags may include an internal power source such as a small battery, which eliminates the need to power the transceiver110from energy received by the tag antenna130. Since conventional RFID tags both passive and active are well known to those skilled in the art, no further elaboration will be given here.

A type of RFID tag called here a suppressible RFID tag will now be described with reference toFIGS. 2A-2B. Unlike a conventional RFID tag of the kind just described, which may respond to the tag reader whenever the tag is within range of the reader, a suppressible RFID tag may respond selectively to the tag reader, in dependence upon a condition that is conveyed by a control signal that is externally provided to the suppressible RFID tag. Thus, to say that a suppressible RFID tag responds selectively means that the tag responds to queries from an RFID tag reader, or does not respond, depending on the state of the control signal.

A control signal, which may be conveyed by the standard voltage levels that represent the logical binary states for an appropriate integrated circuit technology type, may be provided to the suppressible RFID tag200through the port250. In this example, the port250may be a simple electrical connection. A galvanic electrical connection is not required, however, as the control signal may be input to the suppressible RFID tag200by, for example, inductive or capacitive coupling. If the suppressible RFID tag200is active rather than passive, the control signal may be multiplexed onto an electrical connection that powers the suppressible RFID tag200from an external source.

The control signal is provided to the control circuitry240. Subject to the control signal, the control circuitry240effectively enables or suppresses the response of the transceiver210when the suppressible RFID tag200is queried by a tag reader, thereby enabling the suppressible RFID tag200to respond to a tag reader selectively in dependence upon the control signal. For example, if the control signal is a logical high, the control circuitry240may permit or enable the transceiver210to respond to a query from a tag reader. Conversely, if the control signal is a logical low, the control circuitry240may suppress or otherwise inhibit the response of the transceiver210. Of course, the logic may differ from that just described.

FIG. 2Bshows an example of a suppressible RFID tag200with a particular kind of control circuitry240. In this example, the control circuitry240comprises a switching device that, responsive to the control signal, makes and breaks a connection between the tag antenna230and the transceiver210, so that an emission from the transceiver210can or cannot reach the tag antenna230. The switching device may be, for example, a biased PIN diode, a field effect transistor (FET), a MEMS device, or the like; the control circuitry240or the port250may include an appropriate driver for the switching device.

In other embodiments, the switching device may have a single-pole-double-throw structure that connects the transceiver210to the tag antenna230in one state, and, in the other state, connects the transceiver210to a dummy load such as a strip resistor deposited within the suppressible RFID tag200. In this embodiment, emissions from the transceiver210are radiated by the tag antenna230, or suppressed by shunting them to ground through the resistor. Such a switching device can be easily implemented by a pair of diodes or transistors, as would be well known to those skilled in circuit design.

It is not a necessary condition of the invention that the mechanism for suppressing the output of the suppressible RFID tag200involve manipulating the RF path between the transceiver210and the tag antenna230. Rather, in yet other embodiments of the suppressible RFID tag200the control circuitry240may make and break power to the transceiver210, disable the transceiver210at intermediate points internal to the transceiver210, and the like.

FIG. 3shows a block diagram of an exemplary system for locating devices in a given state. For example, the system is suitable for use in a hospital to locate equipment carts or in a warehouse to locate forklifts. Beyond simply locating such devices, however, the system according toFIG. 3provides information regarding the state of located devices. In the example of the hospital equipment cart, the state of a cart may be “in-use” or “available.” States of this sort have two possibilities, and may therefore be represented by a single-bit binary value. Here, the term “in-use” is to be interpreted broadly, encompassing, for example, the case of “reserved,” “disabled,” and the like.

In other cases, states may have more than two possibilities. In the case of forklifts, the state may be a quantized battery voltage. For example, this may have four values: less than 11.5 volts, between 11.5 and 12.0, between 12.0 and 12.5, and greater than 12.5. The four values can be represented by a two-bit binary number. Thus, the four values may be represented by the bit-level contents of a two-bit register associated with the forklift's power supply. For example, register contents ‘00’ may represent a battery voltage of less than 11.5 volts; ‘01’ may represent a battery voltage between 11.5 and 12.0, and so forth.

It is important to emphasize that the examples of the hospital cart and the forklift are provided here only in the interest of describing the invention clearly. These examples will be used again in the description that follows. The invention, however, is not limited in any way to the nature, structure, context, or circumstances of these examples.

As shown inFIG. 3, a monitoring application300, which may execute on a personal computer or other workstation, may provide a GUI to a user, in order that the user may control the operation of the system for locating devices having a given state. Beyond this, the monitoring application300is incidental to the invention.

An RFID edge controller310interfaces to the monitoring application300and to RFID tag readers320and330. RFID tag reader320is used to locate a monitored device340conventionally by reading an RFID tag350that is associated with the monitored device340. An RFID tag may be associated with a monitored device by placing the RFID tag on or nearby the device. For example, the RFID tag may be affixed to the monitored device340or to a structure nearby the monitored device340, built into the monitored device340, and so forth. The RFID tag350may be a conventional, passive RFID tag that responds to queries by an RFID tag reader such as RFID tag reader320independently of the state of the monitored device340. RFID tag reader330is used to determine the state of the monitored device340by reading an RFID tag360associated with the device340, where the RFID tag360responds to queries from an RFID tag reader such as RFID tag reader330selectively, in dependence upon the state of the monitored device340. Although RFID tag readers320and330are shown as being separate RFID tag readers inFIG. 3for descriptive clarity, in practice a single RFID tag reader may be used rather than two separate ones.

As mentioned above, the RFID tag360responds to queries from an RFID tag reader selectively, in dependence upon the state of the monitored device340. In other words, the RFID tag360responds to queries from an RFID tag reader, or not, according to a control signal provided to the RFID tag360, where the control signal indicates the state of the monitored device. Logic370provides the control signal, as described below with reference toFIGS. 4-5.

FIG. 4shows the use of the RFID tag360to monitor the state of a power supply400that powers the monitored device340. This is an example of a case wherein the state of a monitored device may be represented by a one-bit binary value. In a preferred embodiment, the RFID tag360is a suppressible RFID tag like RFID tag200. Here, the state logic370may be a simple threshold or voltage-conversion structure. The output voltage of the power supply400is sensed by the control logic370. When the output voltage exceeds an appropriate threshold, i.e., the power supply is on, the control logic370enables the RFID tag360to respond to queries from an RFID card reader. When the output voltage falls below the threshold, i.e., the power supply is off, the control logic370prohibits the RFID tag360from responding to queries. Thus, a binary value (e.g., above or below the threshold) is indicative of the state of the monitored device340, and the state of the monitored device340may be found by determining the binary value that is indicative of its state.

This approach may be extended to apply to the example of a hospital cart introduced earlier, by using the binary value describing the state of the power supply of an electrical or electronic device on a cart as a proxy for the state of the cart itself. If the power supply is on, as determined by querying the RFID tag360, the cart may be presumed to be in-use. Likewise, if the power supply is off, the cart may be presumed to be available for use.

FIG. 5shows the use of the RFID tag360to monitor the state of an analog device380such as a battery in, for example, a forklift. This is an example of a case wherein the state of a monitored device may be represented by a multi-bit value. Because the state considered in the situation ofFIG. 5has more possible values than the state considered in the situation ofFIG. 4, specific implementations of the control logic370may in practice be more complex.

FIG. 5shows an analog-to-digital (A/D) converter372, which senses a parameter of the analog device380, and provides a quantized digital representation. This representation is loaded into a register371that is associated with the monitored analog device380. Here, the term “associated” means operably connected rather than necessarily geographically proximate. It is not a necessary condition of the invention that the register371be literally a separately identifiable electronic entity.

In the example introduced earlier, a battery that powers or starts a forklift may be the analog device380. Terminal voltage of the battery may be sensed and quantized to, for example, one of sixteen levels or possibilities by the A/D converter372, resulting in a four-bit word that is provided to the register371. Hence, the state of the monitored analog device380may be found by determining the value of a four-bit word.

As shown inFIG. 5, each bit position of the register371has one-to-one correspondence with an RFID tag, here RFID tags360,361,362, and363, which respond selectively to queries from an RFID tag reader, each tag to convey a bit value of the register371. Thus, the bit values of the register371provide control signals for RFID tags360-363. In a preferred embodiment, the RFID tags360-363are suppressible RFID tags like suppressible RFID tag200described earlier.

For example, suppose that the first bit of the register371has the binary value 1, the second bit has the binary value 1, the third bit has the value binary 0, and the fourth bit has the binary value 0. In this case, RFID tags360and361are enabled to respond to queries from RFID tag reader330, whereas RFID tags362and363are prohibited from responding. So, by querying the RFID tags360-363, the RFID tag reader330is able to deduce the contents of the register371, and thereby determine the state of the monitored analog device380by effectively reading the register371.

It is important to note that although the example just given concerns an analog device380, this is not a limitation of the invention. Rather, the invention applies as well when the monitored device provides a direct digital output. In such a case, the A/D converter372would not be needed.

FIG. 6shows aspects of a method for locating devices that have a given state. A user who wishes to locate such a device enters a request through the GUI provided by the monitoring application300(block600). The nearest device is located (block605) conventionally, using an RFID networked-system application, through the capabilities of the RFID tag reader320and the conventional RFID tag350. The state of the located device is then determined (block610) as described earlier, using the capabilities of the RFID tag reader330and the RFID tag360or RFID tags360-363, which respond to queries selectively in dependence upon the state of the located device as described earlier. If the determined state is suitable with regard to the user's request (block615; yes), the located device is identified to the user (block620), and the method returns to await another request (block600).

Otherwise (i.e., the determined state is not suitable; block615, no), the next nearest device is located (block630), using the RFID networked-system application, through the capabilities of the RFID tag reader320and the conventional RFID tag350. The method returns to block610to determine the state of this next-nearest located device, as described above. From this point, the method continues iteratively, until a device having a suitable state is located, or until all of the devices under the purview of the system have been examined without finding a device having a suitable state.

Although the foregoing has described methods, computer program products, and systems for locating devices having a given state, the description of the invention is illustrative rather than limiting; the invention is limited only by the claims that follow.