Method and system for determining location of an item in a storage system - Patents.com

Abstract

A method for locating a plurality of tagged items in a storage system includes scanning the tags at a plurality of power levels with a first antenna (540), identifying each tag of interest found by the first antenna at each of the plurality of power levels (560), scanning the tags at the plurality of power levels with at least one further antenna (540), identifying each tag of interest found by each of the plurality of power levels (560), identifying an antenna that identified each tag of interest at a minimum power level, and estimating a location of each tag of interest using the identified antenna and the minimum power level at which each tag of interest was identified (580).

Description

[Technical field]

[0001] The present disclosure relates generally to locating tags placed within storage cabinets, and more particularly to a system and method for locating radio frequency identification (RFID) tagged items within a multi-shelf cabinet. [Background technology]

[0002] Radio frequency identification (RFID) is a method of radio frequency identification, where data is stored electronically on a tag and is readable by an RFID reader to identify, locate and / or track the tagged item. RFID systems do not necessarily provide the exact location of the tagged item. Instead, they often provide a general location of the tagged item. For example, if a tagged item is placed in a cabinet, an RFID reader often verifies the presence of the tag in the cabinet, but not necessarily on which shelf or in which drawer within the cabinet the tagged item is located.

[0003] RFID readers operate by generating electrical signals, creating an electromagnetic field that interacts with the antenna coil of an RFID tag to interrogate the tag and obtain identifying information from the tag. Summary of the Invention [Means for solving the problem]

[0004] Any discussion of documents, acts, materials, devices, articles or the like which has been included in this specification should not be construed as an admission that any or all of such matters formed part of the prior art base or were common general knowledge in the field relevant to this disclosure prior to the priority date of each claim of this application.

[0005] In one aspect, a method of locating a plurality of tagged items in a storage system is provided, the method comprising: scanning tags at a plurality of power levels with a first antenna, identifying each tag of interest found by the first antenna at each of the plurality of power levels, scanning tags at a plurality of power levels with at least one additional antenna, identifying each tag of interest found by each of the plurality of power levels, identifying an antenna that identified each tag of interest at a minimum power level, and estimating a location of each tag of interest using the identified antenna and the minimum power level at which each tag of interest was identified.

[0006] Scanning for tags with the first antenna at a plurality of power levels may include activating an antenna coil of the first antenna at each of the plurality of power levels. Identifying each tag of interest found by the first antenna at each of the plurality of power levels may include receiving response signals from at least some of the tags of interest at each of the plurality of power levels. The field strength radiated from each of the antennas may vary a predetermined amount with each power level. The power levels may be logical power levels corresponding to actual power levels required for a predetermined antenna range. The method may include deriving a logical power level for each antenna corresponding to an actual power level required to reach a predetermined distance.

[0007] The method may further include calibrating antenna power levels in the storage system. Calibrating antenna power levels in the storage system may include placing a plurality of calibration tags in the storage system, scanning the calibration tags at a plurality of different power levels with each of the antennas, identifying a minimum power level at which each of the antennas finds each of the calibration tags, and setting one or more calibration values ​​for each of the antennas from the identified minimum power levels. Calibrating antenna power levels in the storage system may be repeated with the calibration tags placed at a plurality of different levels in the storage system. Calibrating antenna power levels in the storage system may compensate for differences in antenna coils such that each logical power level for each of the antennas corresponds to substantially the same antenna coil range.

[0008] The method may include setting the tag into a low power mode prior to scanning the tag, the low power mode reducing the number of activated tags in the storage system. The tag may include a memory. The method may further include storing a value representative of the power level at which the tag was first found. The memory may be a timestamp field. The value representative of the power level at which the tag was first found stored in the timestamp field may be a power level ID.

[0009] The method may further comprise: estimating a location of each tag of interest using the identified antenna and a minimum power level at which each tag of interest was identified, comprising: identifying an elevation level of the storage system at which each tag is located; identifying an elevation level of the storage system at which each tag is located may comprise applying a power level offset for each elevation level of the storage system that offsets an antenna power level to a lower elevation level; the power level offset may be applied to a logical power level of each antenna; the method may further comprise: estimating a location of each tag of interest using the identified antenna and a minimum power level at which each tag of interest was identified, comprising: identifying a horizontal position of each tag of interest at the elevation level of the storage system at which the tag was identified; the horizontal position of each tag of interest may be identified as a distance from the antenna having the minimum power level at which the tag was identified, the distance corresponding to the range of the antenna at the minimum power level.

[0010] The first antenna and the at least one further antenna may be disposed on or within the storage system. The storage system may have a height level, and at least some of the height levels may have at least two overlapping antennas with overlapping coils. Each of the at least two overlapping antennas with overlapping coils may have a first loop with a first current and a second loop with a second current that is rotationally opposite to the first current. The overlapping coils may be arranged overlapping such that the loops are aligned along an axis to generate a continuous read zone along the axis. The continuous read zone may correspond to a section of the storage system.

[0011] In another aspect, a system for locating RFID tagged items located within a storage system containing a plurality of RFID tagged items is provided, the system comprising: a plurality of antenna coils associated with one or more elevation levels of the storage system; an antenna controller for powering the antenna coils at power levels corresponding to received power level signals; and a processor in communication with the antenna controller, the processor outputs a plurality of power level signals to the antenna controller to selectively activate each of the antenna coils at a plurality of different power levels, receives response signals from each of the antenna coils corresponding to the respective power levels, identifies each RFID tag found in each received response signal, identifies an antenna coil with a minimum power level that identified each RFID tag of interest, and estimates a location of each RFID tagged item of interest using the identified antenna coil and the minimum power level that identified each RFID tag of interest.

[0012] The descriptions made herein should be understood as relating to some non-limiting embodiments and are not intended to be a description of the entire invention. If there are any provisions that are deemed to apply to all non-limiting embodiments, the applicant / patent owner reserves the right to subsequently delete them from this specification and will not rely on these descriptions for the acceptance or subsequent grant of a patent in any country. [Brief description of the drawings]

[0013] These and other aspects and features will become apparent to those of ordinary skill in the art upon review of the following description of specific non-limiting embodiments in conjunction with the accompanying drawings.

[0014] The detailed description of the illustrative (non-limiting) embodiments will be better understood when considered in conjunction with the accompanying drawings, in which:

[0015] [Figure 1] 1 is a schematic diagram of a non-limiting embodiment of an RFID system.

[0016] [Figure 2A] 1 is a schematic representation of the magnetic field coupling between an RFID antenna and an RFID tag.

[0017] [Figure 2B] FIG. 1 is a perspective view of a storage system having multiple shelves and RFID antennas distributed throughout.

[0018] [Diagram 3] 2 illustrates an exemplary, non-limiting embodiment of a cabinet in which the RFID system of FIG. 1 may be used to locate RFID-tagged items within the cabinet.

[0019] [Figure 4] FIG. 1 is a schematic diagram of a prior art antenna configuration.

[0020] [Diagram 5] FIG. 2 is a flow diagram of a non-limiting embodiment of a method for locating an item in a storage system.

[0021] [Figure 6] 1 is a schematic diagram of a multi-level antenna arrangement for finding tags.

[0022] In the drawings, like reference numbers indicate like parts.

[0023] The drawings are not necessarily to scale and may be illustrated by phantom lines, perspective views, and fragmentary views. In certain instances, details that are not necessary for an understanding of the non-limiting embodiments or that make other details difficult to perceive may be omitted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Reference will now be made in detail to various non-limiting embodiments of methods and systems for locating an item in a storage system. Other non-limiting embodiment(s), modifications and equivalents will be apparent to those skilled in the art in view of the non-limiting embodiment(s) disclosed herein, and such variations should be considered to be within the scope of the appended claims.

[0025] Moreover, those skilled in the art will recognize that certain structural and operational details of the non-limiting embodiment(s) described below may be varied or omitted entirely (i.e., are not required). In other instances, well-known methods, procedures, and components have not been described in detail.

[0026] System Overview

[0027] 1 is a schematic diagram of a non-limiting embodiment of an RFID reader system 100 for locating an item within a section of a storage system. The RFID reader system 100 has an array of antenna coils 102 in communication with an RFID reader 104. The RFID reader 104 includes an antenna controller 106 that selectively powers each antenna coil 108 at a number of different power levels, and a processor 110. The processor 110 receives a number of response signals from the array of antenna coils 102. The response signals are generated in response to one or more interrogation signals from the RFID reader 104. In some non-limiting embodiments, the controller and processor may be provided in a single shared processing unit.

[0028] In addition to the antenna controller 106 and the processor 110, the RFID reader 104 may include various modules 120 that support the operation of the RFID reader 104. These modules may include one or more of a memory 112 (e.g., volatile memory, non-volatile memory, and / or other storage), a communication interface 114 that supports communications between the RFID reader 104 and other devices (e.g., a network interface controller or other form of interface hardware), and a user interface 116. The modules 120 of the RFID reader 104 cooperate with each other by exchanging data over a bus 118.

[0029] The user interface 116 may include display means such as a screen and / or touch screen, along with, for example, a keyboard and / or other buttons / levers, etc. The communication interface 114 may communicate or support communication between the RFID reader 104 and user equipment (not shown). The user equipment may include a computer, laptop, handheld device, tablet, smartphone, etc. The user equipment may include software for receiving and displaying information received from the RFID reader 104, for example, via end user applications in the form of application software such as a mobile "app", website, and / or web application that receives and displays tag location data identified by the RFID reader 104.

[0030] FIG. 2A illustrates the operation of an RFID reader 104 in communication with an antenna coil 208. The antenna coil 208 induces a magnetic field 210 around the coil, as illustrated by the dashed line. The magnetic field 210 defines a read zone around the coil in which an RFID tag can be detected. The magnetic field can couple with the tag antenna of an RFID tag 308 located within the magnetic field either above or below the antenna coil 208. In an exemplary non-limiting embodiment, the antenna coil 208 is positioned on, within, or relative to the shelf floor such that the shelf is considered to lie in the XY plane shown in FIG. 2A. Thus, an RFID tag may be positioned within the generated magnetic field above the shelf floor (in the +Z direction) or below the shelf floor (in the -Z direction), i.e., on a lower shelf.

[0031] FIG. 2B shows a storage system 200 with multiple levels in the form of shelves 202A-202D. Items 220 contained within the storage system 200 have RFID tags 308 that can be read by one or more of the antenna coils 208. The shelves 202A-202D can take other forms, such as, for example, racks, drawers, trays, compartments, etc. For clarity, only one antenna coil per shelf is shown, but this is merely exemplary. Thus, more or fewer (including zero) antenna coils may be provided on each shelf. In some non-limiting embodiments, each shelf has multiple antenna coils to allow for precise item location. Each coil is capable of inducing a magnetic field. This provides a read zone 212 where tags can be detected by the antenna.

[0032] The storage system may be a cabinet or a refrigerator. Another example storage system 300 is shown in FIG. 3 and is a trolley or cabinet 300 in which the items placed are plasma boxes or blood bags 306 affixed with an electronic tag in the form of an RFID tag 308. Each blood bag 306 is placed at a cabinet level (e.g., in a drawer or on a shelf 314). Each tagged item is also placed in a section 310 of the cabinet 300. Each section 310 is in the form of a container, such as a tray 312. In this non-limiting embodiment, each shelf 314 contains a plurality of containers 312. As shown, the exemplary cabinet 300 includes multiple levels in the form of shelves 314 (vertically arranged as labeled by the Y axis), each shelf 314 containing a plurality of trays 312. In the exemplary non-limiting embodiment, the trays 312 are arranged in a row along the width of the cabinet 300 (horizontally arranged as labeled by the X axis).

[0033] Each tray 312 has an elongated shape. It holds a plurality of RFID tagged blood bags 306 stacked lengthwise of the tray 312 across the depth of the cabinet 300 (labeled by the Z axis). Each blood bag 306 has an RFID tag 308 with a tag antenna. In the illustrated example, the blood bags 306 are stacked in the Z direction. The tag antennas of the RFID tags 308 are substantially in the XY plane. In alternative non-limiting embodiments, the trays are arranged and / or stacked in a variety of alternative configurations. For example, each shelf may include two parallel rows of trays.

[0034] Antenna placement

[0035] 4 is a schematic diagram of a prior art antenna configuration 400. In this example, two antenna coils 402 are positioned relative to four trays 404 such that each antenna coil 402 is associated with two of the trays 404. In this configuration, if the first antenna coil 406 provides a signal to the reader indicating the presence of an RFID tag, the RFID tag may be located in either of the first two trays 408, 410 associated with the first antenna coil 406. Similarly, if the second antenna coil 412 provides a signal to the reader indicating the presence of an RFID tag, the RFID tag may be located in either of the two trays 414, 416 associated with the second antenna coil 412. Thus, with this antenna configuration 400, it is not possible to precisely locate an RFID tag in one of the four trays.

[0036] Another drawback of the configuration of Figure 4 is that the maximum power generated by each coil is limited by electromagnetic compatibility (EMC) regulations that dictate limits on electromagnetic emissions at a certain distance from electronic equipment. One solution is to configure two antenna coils 402 so that the current in one coil flows in the opposite direction to the current in the other coil, creating mutually canceling magnetic fields in the far field. However, if both coils are activated simultaneously, resulting in a net zero far field, it becomes impossible to distinguish which of the four trays 404 a tagged item is in.

[0037] In some non-limiting embodiments, each level of the storage system (e.g., each shelf 202A-202D of the storage system 200 of FIG. 2) has overlapping antenna coils such that each item 220 having an RFID tag disposed therein can be powered by one or more coils and / or seen by coils at multiple levels. In use, the antenna coil has a first loop having a first current and a second loop having a second current that is rotationally opposite to the first current. Another antenna coil overlaps the antenna coil such that the loops are aligned along an axis. This can create a continuous read zone along that axis.

[0038] Using such an antenna arrangement, multiple read zones can be created, and in some non-limiting embodiments, the read zones are aligned with sections of the storage system, thereby narrowing down the likely locations where tags of interest are present, and further, such an antenna arrangement can be used to reduce external emissions so that the storage system meets EMC requirements.

[0039] Methodology Overview

[0040] 5 is a flow chart of a non-limiting embodiment of a method 500 for locating an item associated with a detectable tag in a storage system. The method includes performing 520 a calibration of antenna power levels and performing 540 a scan to identify tags detectable by each antenna at different power levels. The method further includes analyzing 560 the scan to identify each tag found by each antenna at the multiple power levels and using the analysis to locate the item 580. In a further step (not shown), the determined location is displayed on the user interface 116 of the RFID reader 104 and / or provided to an end user via the reader's communication interface 114 (e.g., displayed on a user device such as a laptop running an end user application). Each step is described in more detail below.

[0041] Antenna Power Level Calibration

[0042] In typical operation, an antenna coil provides the largest possible read range. This is done by operating at a maximum power level to maximize reception of an RFID tag to determine its presence. However, such an approach does not reveal the location of the tag or its associated item. The range of an antenna coil can be reduced by reducing the power supplied to it. This can be achieved by converting a digital power level signal, such as from the processor 110, to an analog voltage (typically, but not necessarily, between 0-12-15V) that powers the antenna coil. The effective range of an antenna coil varies proportionally to its power level. Thus, for each antenna coil, a calibration of the antenna power level can be performed to identify how the power level correlates with distance.

[0043] For example, in a shelf antenna, different antenna coils may have different shapes. This means that the actual range of each coil is likely to be different. To compare the detection distance between different antenna coils, a calibration measures the power required to read a tag at several distances and sets a calibration value for each antenna coil. Calibration only needs to be performed once for each unique model of storage system. The calibration values ​​for each antenna coil can then be saved and reused for each model.

[0044] First, a number of logical power level steps are identified. A tag reader may have a large number of discrete power levels, e.g., 256 or more. To achieve high resolution, such a large number of power levels can be used. However, this is generally not practical, at least considering the time required to perform the calibration and subsequent measurements. Thus, in some non-limiting embodiments, 2-32 power levels, e.g., 2-16 power levels, are used. For most applications, it has been found that using 2-8 power levels provides sufficient useful resolution of tag distance from each antenna, depending on the size and nature of the antenna and / or storage system.

[0045] To perform the calibration, calibration tags are placed on the storage system. In some non-limiting embodiments, the calibration tags can be individually placed manually. In other non-limiting embodiments, the calibration tags are attached to a movable calibration member that (a) attaches the tags a predetermined distance apart from each other and (b) can be moved together. The movable calibration member is preferably made of a non-metallic material such as cardboard or plastic that does not interfere with the antenna field. In some non-limiting embodiments, the movable calibration member comprises a flat surface such as a sheet of cardboard or plastic. The calibration tags are placed in a line or two-dimensional array. In some circumstances, it may be advantageous for the calibration member to have a shape that extends significantly in each dimension so that the calibration tags can be placed in three dimensions.

[0046] Once the calibration tags are positioned as desired within the storage system, each antenna coil scans for the calibration tags at a number of different power levels, and the relationship between power levels and discovered calibration tags can be used to identify the effective range of each antenna coil at each power level.

[0047] An example of the calibration process is as follows: 1) Calibrate tags starting at the level of the storage system, for example the bottom shelf of a cabinet. 2) For each antenna coil, starting at the lowest power level, increase the power in steps until one or more tags are found, recording the power level at which discovery of each calibration tag occurs. 3) Move the calibration tag to the highest possible position at that level, such as just below the top shelf of a shelf-equipped storage cabinet. 4) Repeat the power level scan of step 2 and record it as the second power level. 5) Moving the calibration tag to another level of the storage system, e.g., a shelf above and / or below the previous level. 6) Repeat the power level scan in step 2 and record it as the third power level. 7) Repeat the above steps for each tier in the storage system.

[0048] With this example in mind, it will be appreciated that the calibration member may be configured in any suitable shape with sufficient calibration tags in suitable locations to obviate the need for steps 3 and 4.

[0049] At the end of such measurement phase, three measurements are obtained, the lowest power level required to find the calibration tag at the closest distance, the intermediate distance and the furthest distance. The raw measurements are converted into a set of logical power level settings to use for a given number of power levels. The logical power levels may differ from the actual power levels of each antenna. Thus, a mapping can be made to account for the different sensitivity of each antenna. Thus, the logical power levels may correspond to distances using known antenna input power. In some non-limiting embodiments, the final power level step is maximum power, so that all remaining calibration tags at any distance within the maximum range are found. In some non-limiting embodiments, the furthest distance is within the same shelf with which the antenna is associated. In other non-limiting embodiments, the furthest distance is within a shelf above and / or below the shelf with which the antenna is associated.

[0050] Each antenna coil may have a different physical power level for each logical power level, so the calibration process helps ensure that discovery information for the same tag on different antenna coils can be compared with power levels input to each antenna coil that approximate the range of the antenna coil.

[0051] For example, antenna coil A may require 100 power settings to find a tag at a distance of 10 cm, whereas antenna coil B may require only 60 power settings to see the same distance. Calibration values ​​can be used to compensate for this difference. Each logical power level corresponds to approximately the same distance from the antenna coil.

[0052] In some non-limiting embodiments, the calibration process includes calibrating the RFID reader power level for the shelf with which the antenna coil is associated, i.e., associating the power level with a respective predefined distance from the antenna coil within the same shelf. In some non-limiting embodiments, the calibration process further includes calibrating the RFID reader power level not only for the shelf with which the antenna coil is associated, but also for shelves below and / or above the shelf with which the antenna coil is associated.

[0053] Scanning of items / tags

[0054] In standard (prior art) operations where the presence of a tag needs to be determined, each tag is found only once on the antenna where it is first found, which is then muted for the remainder of the scan of the other antennas. The reader scans continuously, and even though it may re-recognize a known tag multiple times as part of this process, the tag found message, i.e., the information generated by the RFID reader when it first gets a response from a previously unknown tag as part of the scanning process, is generated only for the first response received. In this type of non-specific location scanning, a tag found message is generated immediately for each initial discovery, and the non-specific location information typically consists of only a single antenna number.

[0055] In contrast, for the non-limiting embodiments described herein, i.e., location specific scanning, each tag may be found by multiple antennas. A tag found message may or may not be generated for any of these actual finds. In some non-limiting embodiments, a tag found message is generated by RFID reader 104 after completing the scan of all antennas at the end of the analysis phase and references a specific location, such as "shelf 4 left". The location specific tag found message may be the only tag found message generated and provided by RFID reader 104 or may be in addition to the non-specific tag found messages associated with the actual antenna reads.

[0056] In some non-limiting embodiments, the item / tag scan searches for tags at multiple different power levels using each antenna coil. The lowest power level of each antenna that finds the tag is recorded. The tag reader performs a full scan of each antenna coil, so that every tag is reconfirmed multiple times with as many antenna coils as can be powered.

[0057] For each find, the antenna coil name and the minimum power level required to find the tag are recorded. By the end of the scan, each tag has a list of tags found on different antennas and at different power levels. This tag find data is stored for subsequent analysis to determine the location of the tag and, therefore, the associated item.

[0058] Scanning can be performed in a number of ways: deep stack power level scanning and shallow stack power level scanning have been identified as two useful variants and are described below.

[0059] In some applications, tags are deeply stacked, meaning that multiple tags are stacked closely together. A common example of deeply stacked tags is document tracking, where each document has a tag. In such situations, a slower but more reliable method is used. To use this method, the tags are first set to a low power mode, for example a quarter power mode, where only a quarter of the tags are activated at a time.

[0060] Below is an example of a process for scanning tags suitable for deeply stacked tags. 1) Set the antenna coil to the lowest power level. 2) Scan all tags visible at this power level. 3) Set the next higher power level. 4) Repeat scanning all tags at this power level. 5) Repeat steps 3 and 4 until the highest power level is reached (until all power levels have been scanned).

[0061] In other applications, tags may be shallowly stacked, meaning that two or more tags are not stacked closely together, such as products in a box with tags attached. Even in a crate full of tagged products, the tags are spaced apart because the size of the product's box keeps them spaced apart. Two tags on two boxes may be adjacent to each other (e.g., with their tags facing each other), but they cannot be stacked any deeper.

[0062] In this situation, a faster method can be used: set all tags to normal power mode, which makes the scanning process 4 times faster than using quarter power mode, as described in the deep stack situation.

[0063] This approach utilizes the tag memory of the tag itself. In this non-limiting embodiment, the tag has a temporary RAM (TRAM) that is used to store tag settings and information. For example, the PJM chip has tag memory that can be used as a timestamp and / or to mute or unmute the tag.

[0064] For the "C-series PJM chips," which are considered suitable chips for use in RFID tags, the timestamp memory is a 16-bit TRAM field. When the tag receives its first command after power-up, the tag reader's timestamp field is stored in the chip memory. When future commands are received, this stored value is returned in the timestamp field of the tag's response.

[0065] Below is an example of a process for scanning tags that utilizes the memory of such tags and is suitable for shallow-stacked tags that have memory in the form of a timestamp field. 1) Set the power level to the lowest and set the timestamp field of the command to the power level ID (e.g., 1 initially). 2) Send one command that includes this timestamp field. 3) Set the next higher power level, increment the power level ID, and set the timestamp field to the new power level ID. 4) Send the command once, including this timestamp field. 5) Repeat steps 3 and 4 for each power level except the final power level. 6) For the final power level, perform a tag identification full scan reading the configured power level ID from the timestamp field of each tag.

[0066] Once the final scan has been performed and all tags have been matched, each tag's response will contain a timestamp, and since each tag's timestamp field is set to the power level ID at which it first came into range, the returned timestamp defines the lowest power level at which each tag was seen.

[0067] location analysis

[0068] Once the tag reader has completed scanning all of the antenna coils, each tag will have data found at different power levels from the antenna coils, which can be used to identify the location of each tag within the storage system.

[0069] For example, Figure 6 shows a tag 602 affixed to an item on a shelf 620. Above the shelf 620 is a higher shelf 622. As shown, the tag 602 can be identified by both the lower shelf antenna 604 and the upper shelf antenna 606. In the illustrated example, because the tag 602 is closer to the lower antenna 604, it is identified by a lower field strength (604') from the lower antenna 604 rather than the higher field strength (606') required for the upper antenna 606.

[0070] There is a known relationship between the physical structure of the storage system and the antenna coils. This relationship can be used to make sense of the multiple discovery information of the tags. The layout of the antenna coils defines a hierarchy having: 1) Shelf. All antenna coils are located on the same horizontal plane. 2) Horizontal location: a group of antennas that only power tags located in a section of a level (such as a shelf) of the storage system (only certain antenna designs provide this capability).

[0071] For each shelf level, a power level offset can be defined to bias the results towards the lower shelf. The power level offset can be an offset applied to the logical power level of the antenna. This is because if the antenna coil is located on, in, at or close to the floor of the shelf, a tag found at similar logical power levels at two different height shelf levels is more likely to be on the lower shelf since the magnetic field couples with tags above the antenna coil (i.e., in the shelf) and below the antenna coil (i.e., in the lower shelf).

[0072] For example, on the bottom shelf, the antennas may have a power level offset of zero; the next shelf may have an offset (e.g., 2), the shelf above that a larger offset (e.g., 4), and so on (e.g., the offset increases in steps of 2 for each shelf). For each tag discovery, the power level offset may be added to the logical power level. So, for example, if a tag is discovered at a logical power level of 1 on the bottom shelf, it will remain at 1, but at the next shelf it will be 3. Using this example, if a tag is halfway between two shelves and discovered by antennas on both shelves at the same logical power level (no offset), the offset will cause the antenna associated with the lower shelf to discover the tag at a power level two steps lower than the discovery from the antenna associated with the upper shelf. Thus, the location is identified as the lower shelf (i.e., lower power). It should be understood that the offset numbers provided are merely examples. In practice, different offsets are used depending on various factors such as the number of logical power levels, the spacing between shelves, antenna sensitivity, etc. Thus, the offset numbers are likely to be different and have more variability.

[0073] For example, referring to the non-limiting embodiment of FIG. 2B, if there are four shelves, each with an antenna coil (or antenna coil arrangement of multiple coils) associated with the floor of each shelf, coil 1 detects a tag located on the first shelf 202D (as this is the lowest shelf, there are no tags below). Coil 2 senses a tag located on the second shelf 202C and a tag located on the first shelf 202D below it, because the distance above coil 2 and within the second shelf is similar to the distance below coil 2 and within the first shelf. Coil 3 detects a tag located on the third shelf 202B and a tag located on the second shelf 202C. In this exemplary non-limiting embodiment, if both coil 4 and coil 3 detect the same tag, the processor 110 of the RFID reader 104 is configured to determine that the tag is located on the third shelf 202B (i.e., biased toward the lower shelf). This is because the read zones 212 formed by the magnetic fields of coil 3 and coil 4 overlap within the third shelf. The overlapping read zones 214 illustrated in FIG. 2B are below the fourth shelf 202A and above and within the third shelf 202B.

[0074] In alternative non-limiting embodiments where the antenna coils are positioned differently, the height level bias may be applied differently. For example, if the antenna coils are positioned on the roof of the shelf and / or if an overlapping read zone is generated on the higher of two shelves, the processor of the RFID reader may be configured to determine that the location of the tag identified by the two antenna coils is on the higher of two adjacent shelves. Similarly, the principles described herein are applicable to other configurations of containers, for example, single-shelf containers having horizontally adjacent sections (e.g., two or more drawers adjacent to each other). It will be understood that antenna configurations associated with the various sections operate such that tags in more than one section are detected by antenna arrangement(s) associated with one section (or tags in more than one section are detected by antenna arrangement(s) associated with one or more sections).

[0075] If horizontal positions are not used, then the definition of each shelf level defines the set of antenna coils at that shelf level, and if horizontal positions are used, then each position at each shelf level defines the set of antenna coils at that position.

[0076] For each tag, all discovery antennas are examined. Even if the horizontal position needs to be determined, the first step is to determine which shelf height level the tag is on.

[0077] To determine the vertical location of a tag, the tag is first assumed to be located at one of a number of discrete storage system height levels (e.g., shelves). A power level offset is applied to each tag's discovery power level to correct for the vertical relationship between the discrete storage system height levels. The tag's height location is then determined to the discrete storage system height level with the lowest logical power level, including the correction for the power level offset.

[0078] If the horizontal location is also to be determined, a second check is performed using only the tag's discovery information at the identified discrete storage system height level. Since all antenna coils are on the same horizontal plane, no power level offset is applied to determine the horizontal location at that level. Thus, the minimum logical power level from the antenna coils determines the horizontal location along the shelf. If the tag has close or equal power levels at the two locations, the tag is determined to be at a location midway between the two antenna coil groups. For example, on a shelf with four horizontal antenna groups, there are three additional locations due to the midpoints between the two groups.

[0079] Once a tag location has been determined, the tag location determined by the processor 110 of the RFID reader 104 may be displayed via the user interface 116 and / or transmitted to an end user application via the communication interface 114. A particular location may be described by a name in the layout, such as "shelf 6" or, if a horizontal location is included, "shelf 2, location 4."

[0080] advantage

[0081] The system described herein locates tagged articles (at an appropriately selected resolution) and provides them to a user to assist in fast and accurate location and identification of tagged articles. Advantageously, location works in storage systems with open shelves. The method is efficient and can be performed with negligible performance penalty over existing systems. The system is scalable to locate any number of tagged articles in a storage system.

[0082] Take the freezer of a blood supply service as an example, traditionally staff would have to manually search for a particular blood bag at a temperature of -40°C. This is not only unpleasant for staff, but also prone to human error and may damage the bag if handled carelessly. With the system described herein, staff can first inquire about the location of the needed blood bag and find out where it is (i.e., the shelf location and the location within the shelf). This can save a lot of time and discomfort, avoid potential damage, and reduce the chance of human error.

[0083] Using a blood shelf management system as another example, tagged blood bags are stored in trays that are over one meter long. The trays are removable and slide into shelves in a multi-tier storage system. Previous RFID systems have at best been able to determine the general location of a tagged blood bag, such as being located in a zone on the left, right, or center of the shelf. The system described herein provides a high resolution method that can precisely determine the location of one or more blood bags of interest.

[0084] It should be noted that the above outlines some of the more suitable non-limiting embodiments. It will be apparent to those skilled in the art that modifications to the disclosed non-limiting embodiments can be made without departing from the spirit and scope thereof. As such, the described non-limiting embodiments should be considered merely illustrative of some of the more prominent features and applications. Other beneficial results can be achieved by applying the non-limiting embodiments in different ways or modifying them in ways known to those skilled in the art. This includes mixing and matching features. Since elements and / or functions between various non-limiting embodiment(s) are expressly contemplated herein, those skilled in the art will understand from this disclosure that features, elements and / or functions of one non-limiting embodiment may be incorporated into another non-limiting embodiment as appropriate, unless otherwise noted above. Although the present specification describes specific arrangements and methods, the intent and concept may be suitably applied to other arrangements and applications.

[0085] In the following claims and the preceding description, unless otherwise required by context, express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in their inclusive sense, i.e., to identify the presence of stated features, but are not used to exclude the presence or addition of further features in various non-limiting embodiments.

Claims

1. 1. A method for locating a plurality of tagged items in a storage system, comprising: scanning tags at a plurality of power levels with a first antenna; identifying, by the first antenna, each tag of interest found at each power level of the plurality of power levels; scanning tags at multiple power levels with at least one additional antenna; identifying, by each of the additional antennas, each tag of interest found at each of the plurality of power levels; identifying the antenna that identified each tag of interest at a minimum power level; and estimating a location of each tag of interest using the identified antenna and the minimum power level that identified each tag of interest.

2. scanning tags at a plurality of power levels with the first antenna includes activating an antenna coil of the first antenna at each of the plurality of power levels; 2. The method of claim 1, wherein identifying each tag of interest discovered by the first antenna at each of the plurality of power levels includes receiving response signals from at least a portion of the tags of interest at each of the plurality of power levels.

3. 3. The method of claim 1, wherein the field strength radiated from each of the antennas varies by a predetermined amount with each power level.

4. 4. The method of claim 3, wherein the power level is a logical power level that corresponds to an actual power level required for a given antenna range.

5. 5. The method of claim 1, further comprising the step of calibrating antenna power levels in the storage system.

6. The step of calibrating antenna power levels within the storage system includes: placing a plurality of calibration tags in the storage system; scanning a calibration tag at a plurality of different power levels with each of said antennas; identifying a minimum power level at which each of said antennas will find each calibration tag; and setting one or more calibration values ​​for each antenna from the identified minimum power level.

7. 7. The method of claim 6, wherein the step of calibrating antenna power levels within the storage system is repeated with the calibration tag positioned at a plurality of different levels within the storage system.

8. 8. The method of claim 5, wherein the step of calibrating antenna power levels in the storage system compensates for differences in antenna coils such that each logical power level for each of the antennas corresponds to substantially the same antenna coil range.

9. 9. The method of claim 1, further comprising the step of setting the tag into a low power mode prior to scanning the tag, the low power mode reducing the number of activated tags in the storage system.

10. the tag includes a memory; 10. The method of claim 1, further comprising the step of storing a value representative of the power level at which the tag was first found.

11. the memory being a timestamp field; 11. The method of claim 10, wherein the value stored in the timestamp field representing the power level at which the tag was first discovered is a power level ID.

12. 12. The method of claim 1, wherein estimating the location of each tag of interest using the identified antenna and minimum power level at which each tag of interest was identified includes identifying an elevation level of the storage system at which each tag is located.

13. 13. The method of claim 12, wherein identifying an elevation level of the storage system at which each tag is located includes applying a power level offset for each elevation level of the storage system that offsets antenna power levels to lower elevation levels.

14. 14. The method of claim 13, wherein the power level offset is applied to a logical power level for each of the antennas.

15. 15. A method according to any preceding claim, wherein estimating the location of each tag of interest using the identified antenna and the minimum power level at which each tag of interest was identified comprises identifying a horizontal location of each tag of interest at a height level of the storage system at which the tag is identified to be located.

16. 16. The method of claim 15, wherein the horizontal location of each tag of interest is identified as a location that is a distance from the antenna having the minimum power level that identified that tag, the distance corresponding to the range of that antenna at that minimum power level.

17. 17. The method according to any of the preceding claims, wherein the first antenna and the at least one further antenna are arranged on or in the storage system.

18. The storage system has a height level; 20. The method of claim 17, wherein at least some of the elevation levels have at least two overlapping antennas including overlapping coils.

19. 20. The method of claim 18, wherein each of the at least two overlapping antennas including the overlapping coils has a first loop having a first current and a second loop having a second current that rotates in an opposite direction to the first current.

20. 20. The method of claim 19, wherein the overlapping coils are arranged with overlapping loops aligned along an axis to produce a continuous read zone along the axis.

21. 21. The method of claim 20, wherein the contiguous read zone corresponds to a section of the storage system.

22. 1. A system for locating an RFID tagged item located within a storage system including a plurality of RFID tagged items, comprising: a plurality of antenna coils associated with one or more elevation levels of the storage system; an antenna controller for powering the antenna coil at a power level corresponding to a received power level signal; a processor in communication with the antenna controller; The processor, outputting a plurality of power level signals to the antenna controller for selectively activating each of the antenna coils at a plurality of different power levels; receiving a response signal corresponding to each power level from each of the antenna coils; Identifying each RFID tag found in each received response signal; Identifying the antenna coil with the lowest power level that identified each RFID tag of interest; and estimating a location of each of the RFID tagged items of interest using the identified antenna coil and minimum power level that identified each of the RFID tags of interest.

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