Object positioning

Abstract

An apparatus for identifying positions of objects, each object having an associated tag. A signal is received from a tag associated with an object as the object is transmitted through one or more coverage areas. A coverage area in which the signal has been received from the tag is identified, and a position of the object is determined as a position corresponding to a path through the localization area passing through the identified coverage area.

Description

[0001] The present invention relates to a method and apparatus for locating objects. The invention relates particularly but not exclusively to the locating of moving objects, such as objects on a moving conveyor belt. The invention has particular but not exclusive application to locating objects in order to sort them.

[0002] The use of radio frequency identification (RFID) tags based on RFID tags attached to objects has become a well-known technology for identifying objects with RFID tags attached. RFID has also been used as a method of locating items with RFID tags attached for many years.

[0003] A range of technologies have been developed for locating items that can use RFID to provide an estimate of the location of an item, many of which rely on ultra-high-frequency (UHF) RFID technology, and each of which has its own advantages and disadvantages.

[0004] Some RFID positioning techniques can be classified as received signal strength (RSS) methods.

[0005] In one such technique, for example, an RFID reader includes a sensor that measures the strength (amplitude) of received signals from active RFID tags. The RFID readers are located at a number of different locations, and the signal measurements performed at the readers for a particular RFID tag are aggregated to provide a triangulated estimate of the three-dimensional position of the tag based on a complex model of the transmission environment. Although this technique can be effective, it is relatively complex and can take a long time to compute.

[0006] In another similar technique, RFID tag signal strength is compared to signal strength from a reference tag at a known fixed location. This approach allows for consideration of many of the environmental changes that affect other RSS techniques described above, although it requires additional tags and relatively complex calibration.

[0007] Some RFID localization techniques can be classified as signal phase based methods.

[0008] These signal phase based methods include, for example, time of arrival (ToA) techniques, where the reader-tag distance is calculated based on the signal's time of flight and the speed of light, thus requiring some form of reader-tag synchronisation.

[0009] A variation of the ToA technique is the time difference of arrival (TDoA) technique, where the difference between arrival times is measured at a known reference point, so no synchronization is required.

[0010] These signal phase-based methods also include angle of arrival (AoA) techniques, where the tag location is determined using the phase difference between signals received by different antennas, which must be half a wavelength (typically about 15 cm) apart.

[0011] Another signal phase-based approach is based on the principle of synthetic aperture radar (SAR), which involves measuring the phase values ​​at different relative positions of the tag and reader antennas and then combining these measurements in the form of a virtual antenna array.

[0012] In the above technologies, it can be generally seen that high-precision positioning using RFID usually requires extensive and complex calibration and / or modeling, active tags, and / or complex reader installation. This complexity leads to potentially high-cost solutions and long calculation times, which is not ideal for many applications, such as those that need to make decisions quickly based on the location of an object.

[0013] One application where this technique is less suitable is, for example, locating tagged items that are moving through an area covered by an RFID reader, especially if the movement is relatively fast. For example, in an application where tagged items are conveyed past one or more readers (e.g., on a conveyor belt, rollers, etc.) to facilitate downstream sorting of these items based on the identities obtained by the readers, the time taken to identify and accurately locate each item may limit the speed at which the items can be conveyed, and therefore the speed at which the items can be sorted. Even in relatively simple applications where items are conveyed one by one through the readers, this limitation may cause problems.

[0014] In scenarios where a large number of tagged objects are transported through the reader coverage area and are relatively randomly distributed within the area (e.g., distributed across the width of a conveyor belt), the task of identifying and accurately locating the tags and the items to which they are attached may be more challenging. An example of such an application is the separation of relatively rapidly conveyed waste packaging items from a mixed stream for the purpose of efficient recycling. However, it should be understood that there are other applications where such sorting may be required.

[0015] Therefore, it can be seen that there is a need for improved methods and / or apparatus for object localization. The present invention is directed to providing at least one method and / or apparatus that at least partially addresses this need.

[0016] In one aspect, the present invention includes an apparatus for identifying the position of a given object among a plurality of objects passing through a positioning area along a direction of travel, each object having an associated tag, the apparatus comprising: means for receiving a signal from a corresponding tag associated with the object as each object is passed through the positioning area, wherein the means for receiving is used to provide a plurality of coverage areas, and is used to receive a signal from a corresponding tag associated with the object as the object travels along a path among a plurality of possible paths through the positioning area that passes through at least one of the plurality of coverage areas; means for identifying at least one of the plurality of coverage areas that has received a signal respectively from a tag associated with the given object; and means for determining the position of the given object as a position corresponding to a path among a plurality of possible paths through the positioning area that passes through at least one of the coverage areas identified by the identification means; wherein at least two of the plurality of possible paths pass through each of the plurality of coverage areas respectively, and wherein the means for determining is used to distinguish between at least two paths that pass through each of the at least one coverage area identified by the identification means to determine the position of the given object.

[0017] The means for receiving may be used to provide multiple coverage areas by the following arrangement: each of the at least two paths passing through each coverage area passes through an associated combination of one or more coverage areas in the multiple coverage areas. The means for determining may be used to determine the position of a given object as one of the at least two paths having an associated combination of one or more coverage areas that are the same as the at least one coverage area identified by the identification means. The means for receiving may be used to provide multiple coverage areas by the following arrangement: at least one of the at least two paths passing through each coverage area passes through an associated combination of at least two coverage areas. The means for receiving may be used to provide multiple coverage areas by the following arrangement: at least one of the at least two paths passing through each coverage area passes through an associated combination including a single coverage area. The means for receiving may be used to provide multiple coverage areas by the following arrangement: the first at least one coverage area is offset relative to the second at least one coverage area in a direction perpendicular to the direction of travel, and the offset distance is less than the size of the first at least one coverage area in a direction perpendicular to the direction of travel. The means for receiving may be used to provide the first at least one coverage area and the second at least one coverage area in the following manner: the first at least one coverage area and the second at least one coverage area do not overlap each other in space. The apparatus for receiving may be used to provide the first at least one coverage area and the second at least one coverage area by providing the first at least one coverage area and the second at least one coverage area in an arrangement where the first at least one coverage area and the second at least one coverage area are spatially separated in the direction of travel, such that the first at least one coverage area and the second at least one coverage area do not overlap each other in space. The apparatus for receiving may be used to provide the first at least one coverage area and the second at least one coverage area by providing the first at least one coverage area and the second at least one coverage area separately in time, such that the first at least one coverage area and the second at least one coverage area do not overlap each other in space. The apparatus for receiving may be used to provide multiple coverage areas by an arrangement where the first at least one coverage area includes multiple coverage areas that are spatially separated from each other in a direction perpendicular to the direction of travel, and the separation distance is less than the offset distance. The apparatus for receiving may be used to provide multiple coverage areas by an arrangement where the offset distance is approximately half of the size of the first at least one coverage area in a direction perpendicular to the direction of travel.

[0018] The means for determining may be used to determine the corresponding position of each of the plurality of objects based on information mapping each of the plurality of possible paths through the positioning area to at least one of the plurality of coverage areas through which the path passes. The means for determining may be used to respectively obtain information indicating the number of times a signal is received from a tag associated with a given object when the given object passes through the corresponding coverage area. The means for determining may be used to distinguish at least two paths that respectively pass through each of the at least one coverage area identified by the identification means based on the number of times a signal is received from a tag associated with the given object when the given object passes through the coverage area. The means for determining may be used to determine the corresponding position of each of the plurality of objects based on information mapping each of the plurality of possible paths through the positioning area that passes through the corresponding coverage area to a corresponding range of possible times a signal will be received from a tag associated with the object when the object passes through the corresponding coverage area. Each range of possible times a signal will be received from a tag associated with the object when the object passes through the corresponding coverage area may be defined by at least one threshold value, the threshold value corresponding to an upper limit or a lower limit of the range of possible times. The means for determining may be used to determine the direction of the object based on the number of times a signal is received from a tag associated with the given object when the given object passes through the coverage area. The means for determining may be used to determine the direction of the object based on information for mapping each of a plurality of possible directions to a respective range of possible times a signal will be received from a tag associated with the object when the object passes through a corresponding coverage area.

[0019] The apparatus may also include means for reading information carried by signals received from respective tags associated with each of the plurality of objects, and means for distinguishing a given object from other objects passing through the locating area along the direction of travel based on information carried by signals received from respective tags associated with each object. The means for determining is also used to determine a respective position of each of the plurality of objects, and wherein the apparatus further includes means for generating a control signal to classify the plurality of objects based on respective information carried by signals received from respective tags associated with each object and read by the reading means, and respective positions determined for each object. The apparatus may also include means for selectively separating the given object from at least one other object passing through the locating area along the direction of travel based on the distinction.

[0020] The tag may be a radio frequency identification (RFID) tag. The means for receiving may be used to receive an RFID signal from the RFID tag. The tag may be a passive RFID tag. The means for receiving may be used to provide each of the plurality of coverage areas by illuminating the coverage area with the RFID signal to activate the passive RFID tag.

[0021] The means for receiving may include a plurality of antennas, each antenna being configured to provide a corresponding coverage area of ​​the plurality of coverage areas.

[0022] In one aspect, the present invention includes a method for identifying the position of a given object among a plurality of objects conveyed through a positioning area along a direction of travel, each object having an associated tag, the apparatus comprising: receiving a signal from a corresponding tag associated with the object at a device for receiving as each object is conveyed through the positioning area, wherein the device for receiving is used to provide a plurality of coverage areas, and is used to receive a signal from a corresponding tag associated with the object as the object travels along a path among a plurality of possible paths through the positioning area that passes through at least one of the plurality of coverage areas; identifying at least one of the plurality of coverage areas that has received a signal respectively from a tag associated with the given object; and determining the position of the given object as a position corresponding to a path among the plurality of possible paths through the positioning area that passes through at least one coverage area identified by the identification device; wherein at least two of the plurality of possible paths pass through each of the plurality of coverage areas respectively, and wherein the device for determining is used to distinguish at least two paths that pass through each of the at least one coverage area identified by the identification device respectively, to determine the position of the given object.

[0023] Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0024] Figure 1 is a simplified illustration of a system for separating objects;

[0025] Figure 2 Yes, you can Figure 1 A simplified illustration of a possible exemplary arrangement of a reader array for use in a system of;

[0026] Figure 3 (a) to Figure 3 (d) shows the Figure 1 Different patterns of localized coverage areas provided by specific arrangements of reader antennas used in the system;

[0027] Figure 4 is through Figure 1 A simplified illustration of the transmission of tags in different parts of the local coverage area in a system of FIG.

[0028] Figure 5 Shown in Figure 1 An idealized example of how additional resolution can be achieved for a given arrangement of reader antennas in a system;

[0029] Figure 6 yes Figure 5An exemplary decision matrix for the example shown;

[0030] Figure 7 It shows that it can be Figure 1 The calibration process used in the system;

[0031] Figure 8 Yes, you can Figure 1 A simplified block diagram of a tag 18 used in a system of; and

[0032] Fig. 9 Yes, you can Figure 1 A simplified block diagram of a control device 22 used in a system.

[0033] Overview

[0034] We will now refer to this by way of example only Figure 1 and Figure 2 A system incorporating the present invention is described in a general overview.

[0035] Figure 1 is a simplified illustration of a system for separating objects, generally shown as 10. The system 10 includes: a conveyor belt 12 for transporting objects 14 to be sorted in the direction shown by arrow A; an array or "cluster" of readers 16 for reading tags 18 attached to the objects 14; a sorting station 20 for sorting the objects 14 based on information read from the tags 18 by the reader array 16; and a control device 22 for controlling the sorting station 20 based on the information read from the tags 18.

[0036] In the described example, objects 18 include items of discarded packaging, and system 10 is a system for sorting discarded packaging for efficient recycling. In such a system, it is beneficial to be able to quickly and efficiently accurately identify and determine the location of each object in order to maximize the throughput of the system and therefore maximize the capacity of the system.

[0037] In the described example, the corresponding tag 18 attached to each object 14 transported by the conveyor belt includes a passive radio frequency identification (RFID), a tag talk only (TTO), a tag, etc. It should be understood that although a passive RFID TTO tag is described by way of example, the tag 18 can include any suitable form of RFID or other type of machine-readable tag. It is also possible that different types of tags 18 can be used on different objects or even the same object.

[0038] The reader array 16 is arranged to read tags 18 attached to objects 14 transported by the conveyor. Thus, in the described example, the reader array 16 is used to read passive RFID TTO tags 18. However, it should be understood that the reader array 16 can alternatively or additionally be used to read other types of tags 18 as well, as desired.

[0039] like Figure 1 As shown, in this example, the reader array 16 includes an array of reader antennas arranged relative to the conveyor belt 12 to illuminate the entire or at least a major portion of the lateral width of the conveyor belt 12 with RF radiation. The reader antennas are arranged to provide a combined coverage area 26, wherein each object 14 on the conveyor belt 12 will pass through the combined coverage area 26 when transported to the sorting station 20. This enables the information stored in the corresponding tag 18 of each object 14 (e.g., a tag identifier associated with the type of object to which it is attached) to be successfully read.

[0040] The control device 22 controls the reader / writer antenna of the reader / writer array 16 to read the information (e.g., item-specific identifier or code) stored in the corresponding tag 18 of each object 14. The control device 22 then distinguishes different objects 14 based on the information read via the reader / writer antenna and received at the control device 22. The control device 22 also determines the corresponding position of each object on the conveyor belt 12 based on the information obtained via the reader / writer antenna of the reader / writer array 16. The control device 22 controls the sorting station 20 to appropriately separate each object 14 based on the corresponding position determined for each object 14 and the information read from the object 14.

[0041] In the example described, the control device 22 is therefore used to provide a reader / writer function to read information carried by the signal received via the antenna. However, it should be understood that each reader / writer antenna can form part of a corresponding local reader / writer, which has its own reader / writer circuitry and logic and provides information read from the received signal to the control device 22.

[0042] The sorting station 20 is shown for illustrative purposes only as a relatively complex sorting station having a robotic arm that, under the control of a control device 22, picks up objects 14 and sorts them into associated bins, etc. based on feedback from the reader array 16. However, it should be understood that the sorting station 20 may be any suitable type of sorting station, such as an air-jet sorting station.

[0043] Advantageously, as will be described in greater detail below, the arrangement of the reader antennas in the reader array 16 is designed to simplify and streamline the determination of the respective position of each object passing through the combined coverage area 26. Specifically, each reader antenna is arranged to provide a respective localized coverage area at a known position relative to the conveyor belt 12, the localized coverage area forming a portion of the combined coverage area 26. This enables the control device 22 to determine the lateral position of each object 14 relative to the conveyor belt 12 based on which (or which) reader antennas have detected and read the tag 18 of that object 14 (combined with information corresponding to the lateral position of the portion of the combined coverage area 26 provided by the corresponding reader antenna).

[0044] Similarly, the relative longitudinal position of each object 14 (e.g., relative to the sorting station 20) can be determined by the control device 22 (and tracked as the conveyor belt 12 moves). This determination can be based, for example, on which reader antenna(s) has detected and read the tag 18 of the object 14, and the time at which the tag 18 was detected. This information can be used in conjunction with, for example, information corresponding to the longitudinal position of a portion of the combined coverage area 26 provided by the corresponding reader antenna and information indicating the speed at which the object 14 is moving. It should be understood that while the relative longitudinal position can be expressed in space (e.g., as a distance from the sorting station 20 or some other fixed point), the relative longitudinal position can additionally or alternatively be expressed in time (e.g., as a period of time before the object arrives at the sorting station 20 or some other fixed point).

[0045] We will now refer specifically to Figure 2 Describes a possible advantageous arrangement of reader antennas in the reader array 16, Figure 2 Yes, you can Figure 1 FIG. 2 is a simplified illustration of one possible exemplary arrangement of a reader array 16 for use in the system 10 .

[0046] like Figure 2 As shown, the reader array 16 includes two banks 16-1, 16-2 of reader antennas 30-1 to 30-6. Each reader antenna 30-1 to 30-6 is arranged to illuminate a corresponding portion of the conveyor belt 12 with RF radiation to provide a corresponding local coverage area R1 to R6 (forming part of a wider combined coverage area 26 that extends the entire lateral width of the conveyor belt 12). Figure 2 As shown, for illustrative purposes, each local coverage area R1 to R6 is shown as a circle and has an inner portion (cross-hatched) and an outer portion (no shading). In practice, the shape of the coverage area may deviate from a circle, depending on, for example, the antenna arrangement, any electronic beam steering applied, and / or other implementation-specific factors.

[0047] The two groups 16-1, 16-2 are separated in the longitudinal direction relative to the conveyor belt 12 to form a first (or "upstream") group 16-1, which is located closer to the upstream end of the conveyor belt 12 than the second (or "downstream") group 16-2. The two groups 16-1, 16-2 are separated by a distance sufficient to avoid interference and / or coupling between the corresponding reader antennas 30-1 to 30-6 of each group 16-1, 16-2. Similarly, the corresponding reader antennas 30-1 to 30-6 of each group 16-1, 16-2 are separated in the transverse direction relative to the conveyor belt 12 by a distance sufficient to avoid interference and / or coupling between those reader antennas 30-1 to 30-6.

[0048] exist Figure 2 In the arrangement shown, the reader antennas 30-1, 30-3, 30-5 of the upstream group 16-1 and the reader antennas 30-2, 30-4, 30-6 of the downstream group 16-2 are arranged relative to each other in a manner that ensures that the entire width of the conveyor belt 12 through which the object 14 may pass is covered by at least one (sometimes two) local coverage areas R1 to R6. The reader antennas 30-1 to 30-6 are arranged relative to each other to provide an arrangement of local coverage areas R1 to R6, in which each local coverage area R1, R3 and R5 of the upstream group is separated from each other; and is separated from but partially aligned with at least one coverage area R2, R4 and R6 of the downstream group 16-2 in the longitudinal direction relative to the conveyor belt 12.

[0049] Specifically, Figure 2 The reader / writer antennas 30-1 to 30-6 shown in the figure are arranged in a pattern that provides partial coverage areas R1 to R6, in which the inner portions of the partial coverage areas R1, R3, R5 provided by the upstream group 16-1 are not aligned with any portion of the partial coverage areas R2, R4, R6 provided by the downstream group 16-2 in the longitudinal direction relative to the conveyor belt 12. In contrast, at least a portion of the outer portion of each partial coverage area R1, R3, R5 provided by the upstream group 16-1 is aligned in the longitudinal direction relative to the conveyor belt 12 with at least a portion of the corresponding outer portion of at least one partial coverage area R2, R4, R6 provided by the downstream group 16-2.

[0050] In more detail, the corresponding reader / writer antennas 30-1 to 30-6 of each group 16-1, 16-2 are arranged at a certain distance, which makes the interval between adjacent local coverage areas R1 to R6 (relative to the transverse direction of the conveyor belt 12) smaller than the transverse width (e.g., diameter) of each coverage area R1 to R6. The reader / writer antennas 30-1, 30-3, 30-5 of the upstream group 16-1 are offset relative to the reader / writer antennas 30-2, 30-4, 30-6 of the downstream group 16-2 (in the transverse direction relative to the conveyor belt 12) to ensure that the entire width of the conveyor belt 12 through which the object 14 can pass is covered by at least one (sometimes two) local coverage areas R1 to R6.

[0051] exist Figure 2 In the exemplary arrangement shown, the reader antennas 30-1, 30-3 and 30-5 of one group 16-1 are arranged to be offset relative to the reader antennas 30-2, 30-4 and 30-6 of another group 16-2, the offset being such that the corresponding center (in the longitudinal direction relative to the conveyor belt 12) of each local coverage area R1, R3 and R5 provided by the upstream group 16-1 is substantially aligned with the center of the gap between two local coverage areas R2, R4, R6 provided by the downstream group 16-2.

[0052] Thus, in operation, due to this offset but partially aligned arrangement of the partial coverage areas of one group 16-1 relative to the partial coverage areas of the other group 16-2, as the tagged object 14 travels on the conveyor belt 12, the corresponding tag 18 will be read by one or possibly two reader-writer antennas 30-1 to 30-6. It can be seen that the particular reader-writer antenna 30-1 to 30-6 or combination of reader-writer antennas 30-1 to 30-6 that reads a particular tag 18 indicates the lateral position of the tag 18, and therefore the lateral position of the object 14 to which it is attached. Similarly, the timing at which each reader-writer antenna 30-1 to 30-6 begins / ends detecting a tag 18 indicates the longitudinal position of that tag 18, and therefore the longitudinal position of the object 14 to which it is attached.

[0053] In effect, the antenna arrangement divides the conveyor belt 12 into a set of overlapping longitudinal regions or antenna "streams" S1 to S6, each of which represents a respective portion of the conveyor belt 12 passing through a respective local coverage area R1 to R6. By overlapping the streams S1 to S6 in the lateral direction, the arrangement effectively divides the conveyor belt into a plurality of narrower "overlap-based" streams or "sub-streams" (which may also be referred to as reader channels or tracks). Thus, a higher spatial resolution or "granularity" is provided with respect to the position of the tagged items 14 (laterally relative to the conveyor belt 12) because the relative position of the items within each stream can be determined (e.g., in the case of the local coverage areas 30-2 to 30-5, as one of three relative positions ("top", "middle" or "bottom")).

[0054] For example, a first tagged item 14 located near the middle of the stream S1 and passing through the local coverage area R1 of the antenna 30-1 will only pass through the inner portion (cross-hatched area) of the local coverage area R1. Conversely, a portion of the stream S1 that passes through the portion farthest from the far edge of the conveyor belt 12 (i.e., closest to the middle) (e.g., Figure 2 The second labeled article 14 of the outer portion (without cross-hatching) of the partial coverage area R1 of the conveyor belt 12 will also pass through the outer portion (as shown) of the partial coverage area R2 closest to the far edge (i.e., farthest from the middle) of the conveyor belt 12. Figure 2 ). Therefore, the first item will be detected by antenna 30-1 only, while the second item will be detected by antennas 30-1 and 30-2. Therefore, control device 22 can determine that the position of the first item is within the reader track corresponding to the non-overlapping portion of stream S1, and the position of the second item is within the reader track corresponding to the overlapping portion of stream S1 and stream S2.

[0055] Thus, the control device 22 can use the information received from the different antennas 30-1 to 30-6 to determine which antenna or antennas have detected the tag 18 of a given object 14, and thereby determine the lateral position of the object 14 relative to the conveyor belt with reasonable spatial resolution.

[0056] Antenna placement / coverage pattern

[0057] It should be understood that while a particular arrangement of reader / writer antennas has been described that provides a localized coverage area pattern having particular advantages, other arrangements of reader / writer antennas that provide different advantages are possible. Reference will now be made by way of example only. Figure 3 (a) to Figure 3 (d) Description can be Figure 1 Some arrangements of reader antennas used in the system, Figure 3 (a) to Figure 3Each of the graphs in (d) shows a different pattern of local coverage area provided by a particular arrangement of antennas.

[0058] Figure 3 (a) shows a particularly simple pattern of local coverage areas R1 to R3 that can be provided by a single group of adjacent reader antennas. In this example, there are three reader antennas arranged to provide three corresponding adjacent local coverage areas R1 to R3 (and therefore three associated antenna streams S1 to S3) extending across the width of the conveyor belt 12.

[0059] In this example, the streams S1 to S3 do not overlap, and therefore the conveyor belt 12 can be physically divided into lanes corresponding to each stream, thereby allowing a relatively simple classification mechanism to be used. Specifically, the conveyor belt 12 can be provided with a physical divider that divides the conveyor belt into separate lanes, wherein a different corresponding lane corresponds to each antenna stream S1 to S3 to ensure that each item passes through the RF field of only one antenna, so that its position can be determined in the relevant stream S1 to S3.

[0060] However, while this arrangement has certain advantages in terms of simplicity and the ability to cover the width of the conveyor belt with a minimum number of reader antennas, the proximity of the reader antennas to each other can result in coupling between adjacent antennas (and / or overlapping RF fields). When the reader antennas are sufficiently separated to avoid such coupling and / or overlap, there may be "blind spots" where tagged items cannot be detected.

[0061] Figure 3 (b) shows another pattern of local coverage areas R1 to R6 that can be provided by two groups of receiver antennas. In this example, six reader antennas (three reader antennas in each group) are arranged to provide six corresponding adjacent local coverage areas R1 to R6 (and therefore six associated antenna streams S1 to S6) extending across the width of the conveyor belt 12.

[0062] Similar to reference Figure 2 The example discussed in Figure 3 In the example of (b), the two groups are separated in the longitudinal direction relative to the conveyor belt 12 to form an upstream group, which is located closer to the upstream end of the conveyor belt 12 than the downstream group. The two groups are separated by a distance sufficient to avoid interference and / or coupling between the corresponding reader / writer antennas of each group. Similarly, the corresponding reader / writer antennas of each group are separated by a distance sufficient to avoid interference and / or coupling between those reader / writer antennas in the transverse direction relative to the conveyor belt 12.

[0063] exist Figure 3In the arrangement shown in (b), the reader / writer antennas of the upstream group and the reader / writer antennas of the downstream group are offset from each other in an arrangement to ensure that the entire width of the conveyor belt 12 through which an object can pass is covered. Figure 2 Unlike the example discussed, the reader antennas are arranged relative to each other to provide a pattern of local coverage areas R1 to R6 in which the antenna streams corresponding to the local coverage areas R1, R3 and R5 of the upstream group do not significantly overlap with the local coverage areas R2, R4 and R6 of the downstream group.

[0064] Therefore, similar to reference Figure 3 (a) The example discussed, the antennas of this example are arranged so that the streams S1 to S6 corresponding to the local coverage areas do not overlap significantly. Therefore, the conveyor belt 12 can be provided with a physical divider that divides the conveyor belt into independent lanes, wherein a different corresponding lane corresponds to each antenna stream S1 to S6 to ensure that each item passes through the RF field of only one antenna, so that its position can be determined in the relevant stream S1 to S6.

[0065] This arrangement avoids Figure 3 The example of (a) has some benefits in terms of the risk of mutual antenna coupling associated with it, and is relatively simple (although more Figure 3 (a) is a little more complex). This arrangement also allows the width of the conveyor belt to be covered using a minimum number of reader antennas.

[0066] Figure 3 (c) shows another pattern of local coverage areas R1 to R6 that can be provided by two sets of receiver antennas. This example corresponds essentially to reference Figure 2 The examples described are therefore not described in detail.

[0067] As reference Figure 2 As stated in Figure 3 In the example of (c), the two groups are separated in the longitudinal direction relative to the conveyor belt 12 to form an upstream group, which is located closer to the upstream end of the conveyor belt 12 than the downstream group. The two groups are separated by a distance sufficient to avoid interference and / or coupling between the corresponding reader / writer antennas of each group. Similarly, the corresponding reader / writer antennas of each group are separated by a distance sufficient to avoid interference and / or coupling between those reader / writer antennas in the transverse direction relative to the conveyor belt 12.

[0068] exist Figure 3 In the arrangement shown in (c), the reader / writer antennas of the upstream group and the reader / writer antennas of the downstream group are offset from each other in an arrangement to ensure that the entire width of the conveyor belt 12 through which an object can pass is covered by the local coverage areas R1 to R6. Figure 3(b) Unlike the example discussed, the reader / writer antennas are arranged relative to each other to provide a pattern of local coverage areas R1 to R6, in which the antenna streams S1, S3, S5 corresponding to the local coverage areas R1, R3 and R5 of the upstream group overlap with the antenna streams S2, S4, S6 corresponding to the local coverage areas R2, R4 and R6 of the downstream group in the longitudinal direction relative to the conveyor belt 12.

[0069] Specifically, the inner portion of the partial coverage areas R1, R3, R5 provided by the upstream group 16-1 is not aligned with any portion of the partial coverage areas R2, R4, R6 provided by the downstream group. However, at least a portion of the outer portion of each partial coverage area R1, R3, R5 provided by the upstream group is aligned in the lateral direction with at least a portion of the corresponding outer portion of at least one partial coverage area R2, R4, R6 provided by the downstream group.

[0070] This arrangement avoids Figure 3 (a) has advantages in terms of the risk of mutual antenna coupling associated with the example and, as described above, with Figure 3 (a) and Figure 3 (b) provides additional positioning resolution compared to the example, although this requires some additional complexity and may require more antennas and / or larger antennas for a given width of the conveyor belt 12. However, the additional spatial resolution provided by the narrower overlap-based reader tracks formed by the overlapping streams is not completely uniform across the conveyor belt, with the reader tracks formed at the edges of the conveyor belt being wider than the reader tracks in the middle. It should be understood that although in the example shown, the reader tracks corresponding to the outer portions of the local coverage area are narrower than the reader tracks corresponding to the center of the local coverage area, the widths of these tracks can be made substantially the same by adjusting the relative offsets between the antennas of each group and the lateral spacing between the antennas.

[0071] Figure 3 (d) shows another pattern of local coverage areas R1 to R6 that can be provided by two sets of receiver antennas. Figure 2 and Figure 3 (c) The examples described have some similarity. For example, Figure 3 The local coverage areas R1 to R6 in (d) are provided by a reader array comprising an upstream group of receiver antennas and a downstream group of receiver antennas, wherein the reader antennas of the upstream group and the reader antennas of the downstream group are offset from each other in the lateral direction in an arrangement to ensure coverage of the entire operating width of the conveyor belt 12.

[0072] In addition, Figure 2 and Figure 3As in the example of (c), the longitudinal distance between the two groups is sufficient to avoid interference and / or coupling between the corresponding reader antennas of each group. Similarly, the distance between the corresponding reader antennas of each group in the transverse direction relative to the conveyor belt 12 is sufficient to avoid interference and / or coupling between those reader antennas.

[0073] However, with Figure 2 and Figure 3 Unlike the example of (c), the placement of the downstream antenna group is somewhat asymmetric relative to the placement of the upstream antenna group. Figure 3 (c) Compared to the antennas providing local coverage areas R2, R4 and R6, the antennas are shifted "upwards" (e.g. Figure 3 (d)), so that the antenna streams S1 to S6 corresponding to each local coverage area R1 to R6 of one group overlap with only one antenna stream S1 to S6 corresponding to one of the local coverage areas R1 to R6 of another group.

[0074] In more detail, the respective antennas of each group are arranged to provide a localized coverage area, wherein approximately half of each coverage area R1, R3 and R5 provided by the upstream group of reader / writer antennas (e.g., Figure 3 (d)) and approximately half of each coverage area R2, R4 and R6 provided by the downstream group of reader antennas (e.g., as shown in Figure 3 (d) The “upper” half shown) is aligned in the longitudinal direction relative to the conveyor belt 12.

[0075] More specifically, the lateral offset between the coverage areas R1, R3 and R5 provided by the upstream group of reader antennas and the coverage areas R2, R4 and R6 provided by the downstream group of reader antennas is substantially equal to half the lateral width of the coverage area (i.e., half the diameter in the case of a circular coverage area).

[0076] Thus, the antennas of this example are arranged so that approximately half of each antenna stream S1, S3 and S5 corresponding to the respective upstream local coverage areas R1, R3 and R5 overlaps approximately half of one of the antenna streams S2, S4 and S6 corresponding to the downstream local coverage areas R2, R4 and R6. Figure 3 In the example shown in (d), this results in the formation of nine independent narrower overlapping reader tracks T01 to T09 of substantially equal width, within which objects transported via the conveyor belt 12 can be positioned.

[0077] For example, using this asymmetric arrangement: labeled items positioned in substream T01 will only pass through local coverage area R1; labeled items positioned in substream T02 will pass through local coverage areas R1 and R2; labeled items positioned in substream T03 will only pass through local coverage area R2; and so on.

[0078] For all of these antenna arrangements, the response of the antenna array to the distribution of items on the conveyor belt can be optimized by adjusting the area of ​​each antenna field and / or the number of antennas in a row that spans the lateral width of the conveyor belt 12. For arrangements in which individual antenna streams overlap, the response of the antenna array to the distribution of items on the conveyor belt can be further optimized based on adjusting the following factors: the number of groups of antennas; the spacing of the antennas and / or the spacing of the fields produced by the antennas in the lateral and / or longitudinal directions relative to the conveyor belt 12; and / or the extent of any overlap between antenna streams (i.e., the extent to which any portion of the local coverage area in one group is aligned in the longitudinal direction with a corresponding portion of the local coverage area of ​​another group). It can therefore be seen that any suitable number of antennas, antenna spacing, and groups of antennas can be used as required to provide an appropriate optimization between lateral positioning resolution and system complexity.

[0079] Furthermore, while all of the arrangements shown employ uniformly distributed antennas for providing uniformly distributed localized coverage areas of similar size, in certain applications, a non-uniform distribution may be beneficial. For example, if the objects being sorted tend to be distributed on the conveyor belt in approximate order of size (e.g., larger objects tend to be at one edge, both edges, or in the center), it may be beneficial to arrange the antennas to have smaller streams (or sub-streams) to cover portions of the conveyor belt 12 where smaller objects are expected.

[0080] Additional spatial resolution

[0081] While the above-described antenna arrangements may be used to provide additional lateral spatial resolution through appropriate placement of the reader antennas, additional lateral positional spatial resolution may also be achieved in any of the above-described arrangements through effective utilization of an appropriate RFID protocol. For example, a protocol that will detect multiple transmissions from a given tag as the tag passes through each local coverage area and is thereby powered by RF radiation from a corresponding antenna may be used to provide additional spatial resolution based on the number of transmissions detected during the passage of a tagged item through a local coverage area.

[0082] Specifically, if in the RFID protocol used, each tag provides a regularly repeating pattern (which encodes a unique identifier associated with the tag) when powered by a reader antenna, then the repeat period, the conveyor speed, and the longitudinal distance that a given tag must travel when passing through the local coverage area will determine the typical number of detections for that tag. Thus, as the tag passes through the local coverage area, the number of times the repeating pattern is read provides a measure of the distance that the tag has passed through the RF field. This distance will be greater near the center of the local coverage area than at the edges, so the number of detections indicates the portion of the coverage area through which the detected item has passed.

[0083] This is only by way of example. Figure 4 It is shown in Figure 4 is a simplified illustration of the transmission of a tag through different parts of the local coverage area. Figure 4 , arrow X shows the transmission of a tag as it passes through an edge portion of the local coverage area, and arrow Y shows the transmission of a tag as it passes through a center portion of the local coverage area. In each case, the transmission of the tag is represented in a square wave type pattern, where each peak represents a corresponding tag transmission of a repeating pattern, and the spaces between the peaks represent delay periods between transmissions of the repeating pattern.

[0084] Thus, a tag in the position indicated by arrow X will make 14 transmissions during its transmission period in the RF field of the reader antenna. Conversely, a tag in the position indicated by arrow Y will make 24 transmissions during its transmission period. Thus, the number of transmissions detected from a particular tag by a reader antenna indicates the location of that tag in the RF field of that reader antenna.

[0085] This can be combined with the overlapping antenna streams described above to provide even higher spatial resolution. Figure 5 shows (in idealized form) how additional spatial resolution can be achieved for one such arrangement in which the antennas are arranged to provide a signal similar to Figure 3 The pattern of the local coverage area shown in (d).

[0086] like Figure 5 As shown, antenna streams S1 to S6 (i.e., corresponding to Figure 3 Each overlapping portion and each non-overlapping portion of the narrower overlapping reader / writer tracks (T01 to T09) shown in (d) respectively has a first ("high tag transmission") portion passing through the center portion of the corresponding local coverage area R1 to R6 and a second ("low tag transmission") portion passing through one of the edge portions of the corresponding local coverage area R1 to R6.

[0087] Thus, in practice, each of the overlap-based reader tracks T01 to T09 can be considered to include multiple (two in this example) even narrower "transmission-occurrence"-based streams or "substreams" (also called reader channels or tracks) V01 to V18, depending on the number of times a transmission from a given tag is detected when the given tag passes through the corresponding local coverage area. Therefore, in order to provide additional spatial resolution in this example, the control device 22 distinguishes between different longitudinal portions of each overlap-based reader track T01 to T09 based on a corresponding comparison of the number of transmissions exhibited by the tag of the tagged item to one or more threshold values ​​when the tagged item passes through the corresponding local coverage area R1 to R6.

[0088] For example, a tagged item within the overlap-based reader track T01 that exhibits a high transmission number (i.e., exceeds the corresponding threshold) during the passage through the local coverage area R1 is considered to be in the lower part of the overlap-based reader track T01 (e.g., Figure 5 ). Therefore, such tagged items are determined to be within the corresponding transmission-based reader track V02. Similarly, tagged items within the overlap-based reader track T01 that exhibit a low number of transmissions (i.e., not exceeding the corresponding threshold) during passage through the local coverage area R1 are considered to be within the upper portion of the overlap-based reader track T01 (e.g., Figure 5 As shown). Therefore, such a tagged item is determined to be within the corresponding reader track V01 based on the transmission occurrence.

[0089] In another example, based on the tagged items within the overlapping reader track T02: exhibiting a high number of transmissions (ie exceeding a corresponding threshold) during passage through the local coverage area R1; and exhibiting a low number of transmissions (i.e. not exceeding the corresponding threshold) during passage through the local coverage area R2; is considered to be located on the upper part of the reader track T02 based on the overlap (such as Figure 5 As shown). Therefore, such a tagged item is determined to be within the corresponding reader track V03 based on the transmission occurrence.

[0090] Similarly, based on the overlapping tag items in reader track T02: exhibiting a low number of transmissions during passage through the local coverage area R1 (ie, not exceeding the corresponding threshold); and exhibiting a high number of transmissions (i.e. exceeding the corresponding threshold) during passage through the local coverage area R2; is considered to be located at the lower part of the reader track T02 based on the overlap (such as Figure 5As shown). Therefore, such a tagged item is determined to be within the corresponding reader track V04 based on which the transmission occurs.

[0091] Thus, it can be seen that the number of transmissions detected by the reader from a particular tag indicates the lateral position of that tag in the RF field of each reader antenna relative to the conveyor belt. By combining the number of transmissions with the overlap-based reading tracks, even higher spatial resolution can be achieved. For example, in Figure 5 In the arrangement shown, this enables the tagged item to be located to a lateral positional accuracy of approximately one quarter of the lateral width (diameter) of the local coverage area of ​​the antenna.

[0092] It will be appreciated that further spatial resolution may be achieved by introducing additional thresholds, effectively dividing the local coverage area into a greater number of smaller lateral regions, where sufficient accuracy may be achieved by counting the number of different transmissions. For example, thresholds may be defined to delimit the expected number of transmissions from tagged items passing through: the central third of the local coverage area (laterally); one of the two outermost sixths of the local coverage area (laterally); and one of the two remaining sixths between the central third and the outermost sixth).

[0093] It will also be appreciated that while the same threshold may be used for each local coverage area, different local coverage area / antenna specific thresholds may be defined, for example, to calibrate for local antenna-to-antenna variations caused by differences in associated local coverage areas. In addition, rather than determining whether a given transmission count is "high" or "low" based solely on a comparison of the transmission count to a single threshold, each transmission count may be compared to one or more ranges of possible transmission count values. For example, a range of values ​​may be defined (e.g., by defining a minimum expected value and / or a maximum expected value) within which any valid transmission count is expected to fall. If the transmission count is below the minimum value (or above any maximum value), then the transmission count may be considered out of range and therefore invalid. Similarly, one range may be defined in which transmission counts are considered high, and another range may be defined in which transmission counts are considered low.

[0094] It should also be understood that while the additional spatial resolution based on the number of detections is important for Figure 3 (c) and Figure 3 Those patterns where the antenna streams shown in (d) overlap are particularly beneficial, but the principles described can be applied to any other pattern of local coverage areas. If desired, the distance between the two outer edges of a given antenna stream (e.g., for Figure 5Any ambiguity in the local coverage area R1 in the conveyor belt (between V01 and V04) may be resolved in other ways. For example, the ambiguity may be resolved by using local coverage areas of different shapes (e.g., elliptical) arranged at a certain angle to the longitudinal axis of the conveyor belt, combined with the time when the item was detected (e.g., relative to a reference time when the tagged item / tag was detected by another sensor before, during, or after the transmission of the local coverage area). It should be understood that the use of multiple readers to provide diagonal coverage areas covering the same track area may also help to improve the positioning accuracy with respect to tags placed in various non-parallel orientations relative to the conveyor belt. Tags placed at a certain angle to the conveyor belt may significantly skew the assumed position (e.g., up to 50% of the reading range at 45°). Therefore, understanding the tag field of view and angle of readers placed at different angles to the conveyor belt may alleviate such problems.

[0095] Decision matrices

[0096] Any suitable method may be used to determine within which antenna stream S1 to S6 a tagged item is located based on transmissions detected from the tagged item, based on overlapping tracks T01 to T09, and / or based on tracks V01 to V09 where transmissions occurred.

[0097] In can Figure 1 In one particularly advantageous method implemented in the system, the control device 22 uses one or more decision matrices to determine the position of a detected tagged item.

[0098] We will now refer to this by way of example only Figure 6 Describe a decision matrix like this, Figure 6 is used for Figure 5 An exemplary decision matrix combining transmission occurrence and overlap-based examples is shown in .

[0099] refer to Figure 6 , when a tagged item is detected within a particular local coverage area R1 to R6, the number of transmissions detected for the tagged item is counted for each local coverage area that the tagged item passes through. The counts for each local coverage area R1 to R6 are then compared with the corresponding antenna-specific thresholds (th1 to th6) or common thresholds to determine whether the number of transmissions is "high" (i.e., greater than or not less than the threshold) or "low" (i.e., less than or not greater than the threshold). The results of the above determinations are then used together with the decision matrix to identify which reader track based on the occurrence the result corresponds to (or most corresponds to).

[0100] Specifically, in Figure 6In the illustration of the decision matrix in , each “X” in a given row and column indicates a corresponding condition (indicated by the header of the column) to be satisfied to identify the tagged item as being within the corresponding occurrence-based reader track V01 to V18 (indicated by the label at the beginning of the row).

[0101] For example, tagged items detected in local coverage areas R5 and R6: Determined to be within the occurrence-based reader track V15 when a detected tag is determined to exhibit a high transmission count in partial coverage area R5 and a detected tag is determined to exhibit a low transmission count in partial coverage area R6; and When a detected tag is determined to exhibit a low transmission count in partial coverage area R5 and a detected tag is determined to exhibit a high transmission count in partial coverage area R6, it is determined to be within the occurrence-based reader / writer track V16.

[0102] Similarly, tagged items detected only in the local coverage area R5: When a detected tag is determined to exhibit a low transmission count in the local coverage area R5, it is determined to be within the occurrence-based reader track V13; When a detected tag is determined to exhibit a high transmission count in the local coverage area R5, it is determined to be within the occurrence-based reader / writer track V14.

[0103] Similarly, tagged items detected only in the local coverage area R6: When a detected tag is determined to exhibit a high transmission count in the local coverage area R6, it is determined to be within the occurrence-based reader track V17; When a detected tag is determined to exhibit a low transmission count in the local coverage area R6, it is determined to be within the occurrence-based reader track V18.

[0104] It can be seen that similar logic also applies to the other occurrence-based reader tracks V01 to V18, and for the sake of brevity, it will not be elaborated in detail.

[0105] Compensation for changes in orientation

[0106] In real-world implementations, the effective shape and effective size of the local coverage area may vary depending on the direction in which a tag on a tagged item passes through the local coverage area. Therefore, the number of transmissions detected in a given reader track may vary over a range of values ​​depending on the direction.

[0107] In can Figure 1In a particularly advantageous method implemented in a system of the type described herein, orientation-induced variations are compensated in advance by a calibration process in which each reader track is systematically fed with tagged items in different orientations. The decision logic for identifying the reader track in which a tagged item is located is then adjusted based on the respective number of transmissions actually detected for each different orientation in each reader track.

[0108] For example, you can adjust Figure 6 The threshold(s) (or ranges) of the decision matrix shown in are set to account for the range of possible numbers of transmissions caused by such directional differences.

[0109] Figure 7 By way of example, it is shown that Figure 1 One of several possible calibration procedures used in the system. Figure 7 In the calibration process, first, at S710, an initial reader track is selected as the current reader track, and at S712, an initial direction is selected as the current direction, and then at S714, a tag item of the current direction is fed to the current track. Then, at S716, the number of transmissions performed in each local coverage area (or at least the local coverage area corresponding to the current reader track) during the transmission of the tag item is counted. Then, at S718, the result of each count is used to adjust (or possibly generate) one or more initial (e.g., default) or previously adjusted decision matrices. The process represented by S714 to S718 is iteratively repeated for each direction in a set of directions that is considered as the current direction (at S722) until it is determined that all directions in the set of directions have been tested (at S720). Then, the process represented by S712 to S718 is iteratively repeated for each reader track that is considered as the current reader track (at S726) until it is determined that all reader tracks have been tested (at S724). Then, the calibration is completed at S728. It should be understood that although a specific process is described for illustrative purposes, there are many possible variations of the process. For example, instead of testing every direction in a given reader track and then changing the reader track, each reader track may be tested for a given direction before changing direction.

[0110] In a particularly beneficial variation of the calibration process, a set of decision matrices may be defined, including a respective decision matrix for each of a plurality of different orientations. In operation, the control device 22 may then select for a given tagged item the decision matrix to be used that best matches the transmission count exhibited by the tagged item. This variation is particularly beneficial because, in addition to being able to more reliably determine lateral position with high precision and accuracy, it also allows for other potentially beneficial features. For example, the control device 22 may infer the orientation of the tagged item based on finding which of the set of decision matrices best matches the measured transmission counts, and control the sorting station to take into account the inferred orientation.

[0111] In another advantageous variation of the calibration process, a set of decision matrices may be defined, including a respective decision matrix for each of a plurality of different conveyor belt speeds (these speed-specific decision matrices may be used in place of or in combination with the direction-specific decision matrices). Thus, transmission counts seen in operation may be compared to one or more of the decision matrices as appropriate to identify the reader track (and possibly tag orientation) based on the reader antenna detecting the tagged item, the number of transmissions counted, and the known conveyor belt ("line") speed.

[0112] By using an extended reader array with additional reader antennas (or antenna groups) or in reference Figure 2 or Figure 3 (a) to Figure 3 Additional benefits can also be achieved by using the antenna array described in (d) with reader antennas at different angles to the "unknown" tag location. The system can then calculate the tag direction using a decision matrix that includes data from all of these different directions and provide additional accuracy to the estimated tag location.

[0113] Further benefits may be achieved by incorporating signal amplitude and / or signal phase thresholds or ranges into the decision matrix and by comparing measurements of actual signal amplitude and / or signal phase to the corresponding thresholds or ranges during operation to provide additional accuracy in the estimated tag position and / or orientation.

[0114] In another advantageous variation, the reader antenna can be moved between read operations. Specifically, in the above method, the article is moved relative to a plurality of static reader groups. It should be understood that the reader groups can alternatively be moved relative to the static article. For example, the method can be used for a scanning process intended to identify the location of certain "contaminated" articles within a group of articles without moving the group of articles. Uncontaminated articles can be moved after the contamination is eliminated.

[0115] Label

[0116] We will now refer to this by way of example only Figure 8Describing the exemplary tag 18 in more detail, Figure 8 Yes, you can Figure 1 A simplified block diagram of a tag 18 used in a system.

[0117] The tag 18 in this example is a radio frequency identification (RFID) integrated circuit for a passive, tag-only (TTO), RFID tag, or the like.

[0118] The RFID tag 18 includes an integrated circuit 810 having a memory 814 having stored therein an identifier 812 that may be unique to the tag 810 or to an item or type of item (eg, a type of packaging) to which the tag 810 is attached.

[0119] Integrated circuit 810 also includes control circuitry 816 for controlling the overall operation of RFID tag 18, and clock 818 for providing timing signals for coordinating the operation of control circuitry 816 and, therefore, the various functions of the tag. In this example, memory 814 includes read only memory (ROM).

[0120] The integrated circuit 810 also includes a transceiver circuit 820 for receiving a radio frequency (RF) excitation signal from an associated RFID reader via one or more external antennas 822 of the tag 18, and for transmitting information from the RFID tag 18 to the RFID reader via the antenna 822 under the control of the control circuit 816. In this example, the transceiver circuit 820 includes an energy harvesting circuit 824 for harvesting energy from the received excitation signal to power the RFID tag 810, and a modulator 826 for modulating a signal carrying information to be sent to the RFID reader. The RFID tag can use load modulation technology to transmit the information to be sent to the RFID reader.

[0121] Control Equipment

[0122] We will now refer to this by way of example only Fig. 9 Describing the control device 22 in more detail, Fig. 9 is a simplified block diagram of the control device 22 .

[0123] like Fig. 9 As shown, the control device 22 includes at least one sorting station interface 910 , at least one reader array interface 911 , at least one network interface 912 , a transceiver circuit 913 , a controller 914 , and a memory 915 .

[0124] The software stored in the memory 915 includes an operating system 916, a communication control module 917, a reader / writer module 918, a positioning module 919, a classification module 920, a calibration module 921, and a decision logic 922. It should be noted that, although the controller 914 is described as operating under the control of multiple discrete software modules for ease of understanding, the functions attributed to these modules may be built into the entire operating system 916, or as separate codes, so that these modules may not be recognized as discrete entities.

[0125] The transceiver circuit 913 can send signals to the sorting station 20 via the sorting station interface 910, and receive signals from the sorting station 20; send signals to the antenna 30 of the reader array 16 and / or associated readers and writers via the reader array interface 911, and receive signals from the antenna 30 of the reader array 16 and / or associated readers and writers; and send and receive signals with an external data network (such as the Internet) via the network interface 912. The operation of the transceiver circuit 913 is controlled by the controller 914 according to the software stored in the memory 915.

[0126] The communication control module 917 controls communication with the antenna 30 and / or associated readers of the reader array 16 to control the reader antenna 30 (and / or associated readers) of the reader array 16 to read the information (e.g., item-specific identifier or code) stored in the corresponding tag 18 of each object 14. The communication control module 917 also controls communication with the sorting station 20, such as sending instructions to the sorting station 20 required to appropriately sort each tagged item.

[0127] The communication control module 917 also controls communications with external data networks, for example, to obtain information for a given tagged item (e.g., stored in a cloud-based database in association with a code corresponding to an item-specific code read from a transmission received from a tag attached to the item). For example, once a unique code associated with a particular RFID tag on an item (e.g., a discarded package, etc.) has been acquired, the code can be compared to an appropriate code database, such as via an Internet link to a cloud storage facility, and the identity of the product associated with the item and / or other relevant information can be determined (e.g., other information from which the tagged item's sorting destination can be derived, such as: information about the product / packaging type; information about the product / packaging recyclability; and / or information that simply identifies a particular sorting bin).

[0128] It should be understood that while cloud storage and access to product data has advantages, such as allowing convenient access from any web-enabled device (e.g., a web-based client or application that allows a user to visualize items that have been detected at a particular time and location), similar databases may also be provided locally without access to the Internet.

[0129] The reader module 918 controls the emission of RF radiation emitted from the reader antenna 30 to provide local coverage areas R1 to R6. The reader module 918 also processes data received from the reader array 16 to read information carried by transmissions from tagged items received via the antenna 30 of the reader array 16. The reader module 918 is also responsible for counting the corresponding number of transmissions received for each tagged item via each antenna 30. This processing may include, for example, reading a unique code associated with a tagged item and associating the code with information identifying each antenna 30 via which information is acquired and / or identifying the number of transmissions received for the tagged item via each antenna 30.

[0130] The positioning module 919 uses the information obtained from the transmission from the tagged items to determine in which antenna stream S1 to S6 and / or reader track T01 to T09 / V01 to V18 each tagged item is located. The positioning module 919 also identifies the position (time and / or space) of each tagged item in the direction of travel of the conveyor belt to ensure that the time of sorting performed by the sorting station 20 can be relatively accurately controlled to properly sort each tagged item at the correct time.

[0131] The classification module 920 is responsible for obtaining appropriate item / product related information (e.g., from an external network) based on the information read from each tagged item. Then, the classification module 920 controls the classification station 20 to classify the tagged items based on the positioning information and item / product related information obtained by the positioning module 919, so as to classify the tagged items appropriately.

[0132] The calibration module 921 is responsible for (for example, as reference Figure 7 and elsewhere described) calibration process control system 10.

[0133] The decision logic 922 includes logic for the positioning module 919 to determine in which antenna stream S1 to S6 and / or reader track T01 to T09 / V01 to V18 each tagged item is located (e.g., referring to Figure 6 and one or more decision matrices described elsewhere).

[0134] Modifications and Alternatives

[0135] Detailed embodiments and many possible variations have been described above. As will be appreciated by those skilled in the art, many modifications and substitutions may be made to the above-described embodiments and variations while still benefiting from the inventions embodied therein.

[0136] For example, it should be understood that, while two or more reader antenna groups may be arranged as described above to provide overlapping antenna streams and associated additional spatial resolution, a similar effect may be achieved by temporally modulating the lateral position of the coverage area provided by the antenna of a single group. For example, the reader array may be used to mechanically reciprocate a single group of antennas between two or more corresponding configurations, in which the lateral position of the antenna and thus the associated coverage area may also move. In this example, the antenna stream associated with one of the corresponding configurations will be longitudinally "overlapped" with the antenna stream associated with one or more of the other corresponding configurations to provide a narrower reader track as described above. Then, substantially as described above, by processing the corresponding group of antenna streams associated with each configuration in the same manner as the corresponding group of antenna streams associated with each group in the previously described example, the control device in the system implementing this time-division multiplexing configuration may identify the narrower reader track where the tag item is located. In addition, this time-division multiplexing configuration may be achieved by electronically manipulating the local coverage area instead of mechanically moving them. Although this approach may add additional complexity, it may also be beneficial because reducing the number of antennas may make the implementation more compact and potentially more cost-effective.

[0137] In another variation, different groups of antennas (corresponding to the different groups described above) may be arranged to provide respective group coverage areas at the same longitudinal position relative to the conveyor belt, wherein the antenna stream associated with one of the above group coverage areas will longitudinally "overlap" with the antenna stream associated with one or more of the other group coverage areas to provide a narrower reader track substantially as described above. However, to avoid coupling, different antenna groups may be turned on or off in a time-multiplexed manner, or other forms of antenna group-specific signal modulation may be used to avoid coupling or interference.

[0138] It should also be understood that, although passive RFID tags offer certain advantages in terms of simplicity, efficiency, and ease of use, in some applications, the tag is not necessarily a passive RFID tag. For example, an active RFID tag may be used in some scenarios. In addition, the tag may be any other machine-readable tag, such as a quick response (QR) code, a barcode, or a tag readable using a different communication protocol (e.g., other near-field communication (NFC) protocols).

[0139] In one variation, the relative lateral position of a particular tag on the conveyor belt can be at least approximately determined based on the difference in transmission times calculated by each of the plurality of readers and the relative lateral positions of the readers on the conveyor belt.

[0140] For example, if the number of transmissions counted by the first reader (the lateral distance between the antenna centroid and the conveyor belt edge is d1) for a particular tag is x1, and the number of transmissions counted by the second reader (the lateral distance between the antenna centroid and the conveyor belt edge is d2) for the tag is x2, then it can be estimated that the distance of the tag from the second reader is x2 / x1 times that from the first reader (where x2>x1). Specifically, the position of the tag from the conveyor belt edge can be estimated as:

[0141] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

Claims

1. A device for identifying the position of a given object among a plurality of objects passing through a locating area along a direction of travel, each object having an associated tag, the device comprising: means for receiving a signal from a respective tag associated with each object as the object is conveyed through the location area, wherein the means for receiving is configured to provide a plurality of coverage areas and to receive the signal from the respective tag associated with the object as the object travels along one of a plurality of possible paths through the location area that passes through at least one of the plurality of coverage areas; means for identifying at least one of said plurality of coverage areas that has received a signal from said tag associated with said given object, respectively; and means for determining the position of said given object as a position corresponding to one of said plurality of possible paths through said location area passing through said at least one coverage area identified by said identifying means; wherein at least two of the plurality of possible paths pass through each of the plurality of coverage areas respectively, and wherein the means for determining is used to distinguish the at least two paths passing through each of the at least one coverage area identified by the identification means respectively, so as to determine the position of the given object.

2. The device according to claim 1, wherein: The means for receiving is used to provide the multiple coverage areas by the following arrangement: each of the at least two paths that pass through each coverage area respectively passes through an associated combination of one or more coverage areas among the multiple coverage areas; and wherein the means for determining is used to determine the position of the given object as one of the at least two paths that has an associated combination of one or more coverage areas that is the same as the at least one coverage area identified by the identification means.

3. The device according to claim 2, wherein: The means for receiving is configured to provide the plurality of coverage areas by arranging that at least one of the at least two paths passing through each coverage area respectively passes through an associated combination of at least two coverage areas.

4. The device according to claim 2 or 3, wherein: The means for receiving is configured to provide the plurality of coverage areas by arranging that at least one of the at least two paths passing through each coverage area, respectively, passes through an associated combination comprising a single coverage area.

5. Apparatus according to any one of the preceding claims, wherein: The means for receiving is configured to provide the plurality of coverage areas by arranging: a first at least one coverage area to be offset relative to a second at least one coverage area in a direction perpendicular to the direction of travel, the offset distance being smaller than a dimension of the first at least one coverage area in the direction perpendicular to the direction of travel.

6. The device according to claim 5, wherein: The means for receiving is configured to provide the first at least one coverage area and the second at least one coverage area in such a manner that the first at least one coverage area and the second at least one coverage area do not spatially overlap each other.

7. The device according to claim 6, wherein: The device for receiving is used to provide the first at least one coverage area and the second at least one coverage area in the following manner: the first at least one coverage area and the second at least one coverage area are provided by arranging the first at least one coverage area and the second at least one coverage area to be spatially separated in the direction of travel, so that the first at least one coverage area and the second at least one coverage area do not spatially overlap with each other.

8. The device according to claim 6 or 7, wherein: The means for receiving is configured to provide the first at least one coverage area and the second at least one coverage area by providing the first at least one coverage area and the second at least one coverage area separately in time so that the first at least one coverage area and the second at least one coverage area do not overlap each other in space.

9. The apparatus according to any one of claims 5 to 8, wherein: The means for receiving is configured to provide the plurality of coverage areas by the following arrangement: the first at least one coverage area comprises a plurality of coverage areas spatially separated from each other in a direction perpendicular to the direction of travel, the separation distance being less than the offset distance.

10. The apparatus according to any one of claims 5 to 9, wherein: The means for receiving is configured to provide the plurality of coverage areas by an arrangement in which the offset distance is approximately half a dimension of the first at least one coverage area in a direction perpendicular to the direction of travel.

11. Apparatus according to any one of the preceding claims, wherein: The means for determining is used to determine a corresponding position of each of the plurality of objects based on information mapping each of the plurality of possible paths through the positioning area to the at least one coverage area of ​​the plurality of coverage areas through which the path passes.

12. Apparatus according to any one of the preceding claims, wherein: The means for determining is used to respectively obtain information indicating the number of times a signal is received from the tag associated with the given object when the given object passes through a corresponding coverage area.

13. The device according to claim 12, wherein: The means for determining is for distinguishing the at least two paths passing through each of the at least one coverage area identified by the identification means based on the number of times a signal is received from the tag associated with the given object when the given object passes through the coverage area.

14. The apparatus according to claim 12 or 13, wherein: The means for determining is used to determine the respective position of each of the plurality of objects based on information for mapping each of the plurality of possible paths through the positioning area that passes through a corresponding coverage area to a respective range of possible times that a signal will be received from a tag associated with the object when the object passes through the corresponding coverage area.

15. The device according to claim 14, wherein: Each possible range of times a signal will be received from a tag associated with an object when the object passes through the corresponding coverage area is defined by at least one threshold value corresponding to an upper or lower limit of the range of possible times.

16. The apparatus according to any one of claims 12 to 15, wherein: The means for determining is for determining a direction of the object based on a number of times a signal is received from the tag associated with the given object when the given object passes through the coverage area.

17. The device according to claim 16, wherein: The means for determining is for determining the direction of the object based on information for mapping each of a plurality of possible directions to a respective range of possible times a signal will be received from a tag associated with the object when the object passes through a corresponding coverage area.

18. Apparatus according to any one of the preceding claims, wherein: The apparatus also includes means for reading information carried by the signals received from the respective tags associated with each of the plurality of objects, and means for distinguishing between the given object and other objects passing through the positioning area along a direction of travel based on the information carried by the signals received from the respective tags associated with each object.

19. The apparatus according to claim 18, wherein: The means for determining is used to determine the corresponding position of each object in the plurality of objects, and wherein the device also includes means for generating a control signal to classify the plurality of objects based on the corresponding information carried by the signal received from the corresponding tag associated with each object and read by the reading device and the corresponding position determined for each object.

20. The apparatus of claim 18 or 19, further comprising means for selectively separating the given object from at least one other object conveyed through the locating area along a direction of travel based on the differentiation.

21. Apparatus according to any one of the preceding claims, wherein: The tag is a radio frequency identification (RFID) tag, and wherein the means for receiving is for receiving an RFID signal from the RFID tag.

22. The apparatus according to claim 21, wherein The tag is a passive RFID tag, and wherein the means for receiving is used to provide each coverage area of ​​the plurality of coverage areas by illuminating the coverage area with an RFID signal to activate the passive RFID tag.

23. Apparatus according to any one of the preceding claims, wherein: The means for receiving includes a plurality of antennas, each antenna being configured to provide a corresponding coverage area of ​​the plurality of coverage areas.

24. A method for identifying the position of a given object among a plurality of objects passing through a locating area along a direction of travel, each object having an associated tag, the apparatus comprising: receiving, at the means for receiving, a signal from a corresponding tag associated with each object as the object is conveyed through the location area, wherein the means for receiving is configured to provide a plurality of coverage areas and to receive the signal from the corresponding tag associated with the object as the object travels along one of a plurality of possible paths through the location area that passes through at least one coverage area of ​​the plurality of coverage areas; identifying at least one of the plurality of coverage areas that has received a signal from the tag associated with the given object; and determining the position of the given object as a position corresponding to one of the plurality of possible paths through the positioning area that passes through the at least one coverage area identified by the identification device; wherein at least two of the plurality of possible paths pass through each of the plurality of coverage areas respectively, and wherein the means for determining is used to distinguish the at least two paths passing through each of the at least one coverage area identified by the identification means respectively, so as to determine the position of the given object.

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