WO2010097822A1

WO2010097822A1 - Method and station for reading a plurality of rfid tags

Info

Publication number: WO2010097822A1
Application number: PCT/IT2009/000072
Authority: WO
Inventors: Stefano Bergonzi
Original assignee: Actvalue Consulting & Solutions S.R.L.
Priority date: 2009-02-26
Filing date: 2009-02-26
Publication date: 2010-09-02

Abstract

A method for the automatic reading of a plurality of RFID tags in a limited volume, comprising the sliding according to an axis (26) along the volume of a tilted circular antenna (27) that embraces the volume while a relative rotation is applied around said axis between antenna and plurality of tags in the volume, in which the scanning speed of the antenna along the axis is automatically varied according to the density of the tags detected during the scanning. A reading station (10) is also described.

Description

"METHOD AND STATION FOR READING A PLURALITY OF RFID TAGS"

The present invention relates to an innovative method and to a station for the automatic reading of a high number of identification tags of the RFID (Radio Frequency IDentification) type present inside a limited volume. The tags can, for example, be inside articles in containers of the ROLL-CONTAINER type. The roll-container is a container widely used in the logistics field to transport different types of articles. Such container is typically a parallelepiped, of varying dimensions, with two or more side panels and wheels for moving . A growing demand exists to be able to carry out a scan and identify the contents of the containers, envisaging that the contained articles have RFID tags permitting automatic and univocal identification of the single articles. Depending on the type of articles (size, packaging possibilities, etc.), the number of tags that can be present inside a scanning volume can vary from a few dozen to many thousands. A typical case occurs in industrial laundries where the articles to be washed (including small ones, such as, for example, napkins) , each identified by a tag, arrive from clients in bags that are placed in roll-containers, so that one roll-container can contain a really large number of tags, with the tags arranged mixed up in the entire roll-container volume.

This makes it really hard to be able to automatically process the roll-containers to perform the reliable reading 000072

of all the tags. Attempts have been made in prior art, but the roll-container often has to be emptied to pass the single articles (or a more reduced number of articles) sequentially through a reading station before again introducing them into the roll-container.

It is always also extremely hard to make a scan that manages to reliably identify, in the least possible time, a very large number of tags in a limited volume. In the known systems, the reading of the articles is therefore nearly always done individually or in groups with tunnel type reading systems that have a conveyor belt or similar systems of smaller dimensions and which in any case call for such reading times that the identification of the contents of a single roll-container or of another equivalent volume implies an excessively high amount of time. Such known process obviously calls for the articles to be handled, with consequent operating inefficiencies. Reading systems have also been, presented (e.g., in WO 2004/074873) that envisage the use of a circular antenna that embraces a container that is made to rotate and covers it from top to bottom to read the tags contained in it . Such systems do not however solve the problem of the automatic processing of roll-containers and/or of a large number of tags in a limited volume . EP 1376446 describes a method and an apparatus with a cylindrical antenna into or from which containers containing tags are dropped or lifted. In the case of lifting, an entire section of a conveyor with on it the container to be scanned is moved towards the cylindrical antenna. Such system cannot in fact obtain good results, especially when scanning occurs near the bottom of the container. Furthermore, it is unsuitable for moving roll-containers . EP 1139277 describes a scanning of objects with tags in pallets by means of one or more antennas, including ring shaped. No solution to the automatic treatment of roll- containers is suggested.

A fault of the mentioned known systems is also that in order to be able to identify a relatively high number of tags, the scanning speed must be very low and the scanning times are therefore unsatisfactory, especially for automated applications .

Furthermore, the tags are often arranged mixed up in the volume to be scanned and scanning areas are therefore found with an accumulation of many tags and others with only a few tags. This is often confusing and makes the above-mentioned known systems even more inefficient. The general object of the present invention is to overcome the above-mentioned drawbacks by providing an optimized method for detecting a large number of tags arranged in a limited volume, in particular mixed up and with even big variations in density. A further object is to provide a station that applies the method in an efficient way in the automatic processing of roll-containers. In view of such object, the idea occurred to realize, according to the invention, a method for the automatic reading of a plurality of RFID tags in a limited volume, comprising allowing a tilted circular antenna to slide according to an axis along the volume and which embraces the volume while a relative rotation is applied around said axis between antenna and plurality of tags in the volume, in which the scanning speed of the antenna along the axis is automatically varied according to the density of the tags detected during scanning.

Furthermore, the idea also occurred to realize a station for the automatic reading of a plurality of RFID tags in a limited volume, comprising a tilted circular antenna that is motorized to slide according to an axis along the volume to embrace the volume and motorized means for the relative rotation, around said axis, of antenna and plurality of tags in the volume, characterized in that it comprises a control unit which during scanning commands the variation of the scanning speed of the antenna along the axis according to the density of the tags detected during scanning.

To make the explanation of the innovative principles of the present invention and its advantages with respect to prior art clearer, a description will be provided below, with the aid of the attached drawings, of a possible exemplary embodiment applying such principles. In the drawings:

- figure 1 represents a schematic view of a possible reading station applying the method according to the invention;

- figure 2 represents a schematic view in cross section of a part of the station in figure 1; - figure 3 represents a side view, schematic and partial, of an area of the station in figure 1;

- figures 4 and 5 represent perspective views, from above and below respectively, of a container for the articles to be introduced in the station of figure 1; - figure 6 represents a view from below of a wheeled platform that can be associated with, or which can represent the bottom of a container similar to that shown in the figures 3 and 4. With reference to the illustrations, figure 1 shows a reading station, generically identified by 10.

The station comprises a linear transfer section 11, or horizontal conveyor, for moving one or more stacked roll- containers 12 from an entrance area 13 to an exit area 14. For the sake of convenience, hereinafter reference will also be generically made to a roll-container when this is in fact formed of several containers, one on top of the other. Slides or other known manual or automatic access systems, can be provided to sequentially convey the roll-containers to the entrance area and remove them from the exit area.

Between entrance and exit, the transfer section 11 crosses a reading chamber 15 which is advantageously identified by a metal wall structure (continuous, cage, mesh, etc.), indicated by a broken line, which provides both physical protection to the reading area, to prevent for example any risks to persons, and screening against excessive electromagnetic interferences.

Inside the reading chamber 15 is a lifting and rotation unit 16 and a reading unit 17. The entire station 10 is governed by an electronic control unit 18 substantially known to prior art, e.g., with a suitably programmed micro- controller, easily imaginable by the technician from the following description, and not therefore further described or shown here. As can also be seen in 2, the transfer section 11 comprises a pair of rails 20, 21 for the guided sliding of the lower wheels 19 of the roll-container and a corresponding chain conveyor for fastening onto and dragging the roll-container along the rails. In particular, the chain conveyor advantageously comprises a pair of motorized chains 22, 23 that slide parallel and close to the rails 20, 21 to engage the containers close to the wheels with an engagement protrusion 24, 25 of a plurality of engagement protrusions arranged at intervals along the chains. This way, once the roll-container has been at least partially pushed on the rails, its movement becomes automatic, controlled by the control unit 12 which operates the conveyor motor. Known sensors (e.g., with photocell, proximity, etc.), not shown, can be present to detect the position of the roll-container along the rails (e.g., at the start, in the correct position in the reading chamber, and at the exit of the transport section) and help control movement. As will be clear later on, the lifting and rotation unit 16 present in the reading chamber, lifts the container on command from the transport system and rotates it according to a vertical axis 26. The reading unit 17 comprises a tilted circular reading antenna 27 with its centre coaxial with the axis 26 and which is moved vertically by means of a motorized carriage 28 that runs along vertical guides 29.

Advantageously, the ground impression of the antenna 27 inscribes with little play the plan of the roll-container. The rotation of the container and the sliding of the antenna are synchronous so as to couple all the RFID tags in the container and receive their data to be read. The operation and the structure of the electronic RFID reading system is of the type substantially known to prior art and will not be further shown or described here. The lifting of the container is such as to allow minimizing the reading interferences caused by the metallic masses underneath the roll-container, so as to also obtain a reliable reading of the tags close to the bottom of the container. Figure 3 shows the lifting and rotation unit 16 in greater detail. This unit is advantageously made with a pantograph lift 30 (also called "scissors type") . In particular, the lift comprises two pairs of arms pivoted X fashion and which support a horizontal platform 31. A motorization 32, with nut screw brings the lower extremities of the arms of each X closer together (thanks to a carriage sliding along guides 33) so as to move the platform 31 vertically and keep it horizontal (thanks to a carriage sliding of the upper extremities of the opposite arms along guides 34 on the platform) .

On the platform 31 is fitted a vertical shaft 35, coaxial with the axis 26 and motorized with a gearmotor 36 to turn around the axis. At the upper extremity of the shaft 35 is a horizontal plate 37 for supporting and lifting the roll-container. The shaft 35 is long enough to allow suitably separating the roll-container from the underlying masses when the lift 30 is operated, so as to reduce their interferences during the readings. Furthermore, thanks to the lifting, the antenna 27 can reach a lower height such T/IT2009/000072

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as to also be able scan the tags on the bottom of the container without encountering obstacles . To reduce the interferences, the plate is advantageously made of plastic material . The figure 3 shows, by means of a broken line, the lifting effect of the plate 37 when the lift is operated. Advantageously, the plate is round in shape, slightly tapered upwards, with an upper engaging groove 38 that extends along a diameter to be accommodated in a complementary impression on the bottom of the roll-container. This structure has been found advantageous for a rapid and reliable lifting and rotation of a roll-container keeping it centered. The use of a plate of small diameter with respect to the size of the container base permits minimizing the masses of interference underneath the container during rotation and reading .

The figures 4 and 5 show a container for use in the machine. It is made of plastic, to prevent interferences during reading, and is suitably ribbed for the required sturdiness.

The container can have on the bottom an impression 39 substantially specular to the plate 37 (so the plate is accommodated with little play in the impression during lifting) and have the castor wheels 19 constrained. Several containers can be stably placed one on the other until a maximum height is reached for entrance to the reading chamber .

Alternatively or in addition to equipping the container directly with the wheels and with the impression 39, a platform 40 can be envisaged, shown in the figure 6, it too pressed in plastic, having underneath the impression 41 specular to the plate 37 and castor wheels 19. This way, the station 10 can also accommodate different containers, by simply placing them on the platform 40 to make "roll- containers" . Furthermore, the containers can thus be without the dimensions of the wheels, making them easier to stack. Of course, it can also be envisaged that only the lowermost container have wheels, and the platform be avoided.

In one way or the other, during the use of the reading station, the roll-containers are moved to the entrance 13 until at least the front wheels are engaged in the horizontal conveyor. The control unit 18 controls the conveyor to move the roll-container until this is in the correct position in the reading chamber. After this, the conveyor is stopped and the lift 30 is operated to engage the plate 37 on the bottom of the roll-container and lift it into the reading position. In this position, the wheels no longer interfere with the guides of the horizontal conveyor and the motor 36 can be operated to continuously turn the roll-container around the axis 26. This axis passes substantially through the centre of gravity of the container. The lower engagement avoids swerving and ensures centering.

During the rotation of the roll-container, the antenna is moved vertically to cover the entire roll-container (or the stacked roll-containers) and to read all the RFID tags present in the scanned volume. The combination of container rotation and vertical movement of the tilted antenna permits the reliable coupling of the antenna with all the tags present in the volume . By making the containers turn instead of the antenna, power connection problems are avoided between the antenna and the transceiver apparatus of the unit 12, and these can thus be made using simple flexible wires instead of with sliding contacts. Once reading has terminated, the rotation is stopped in the departure position and the roll-container is placed on the horizontal conveyor, with the wheels in the sliding guides. The horizontal conveyor starts again and the roll-container is moved to the exit 14 where it is removed from the reading station by means of known means (manual, automatic or semiautomatic) . The station is ready to accommodate the next roll-container.

According to the method of the present invention, the scanning speed of the antenna along the axis 26 is varied repeatedly by the control unit 18 according to the density or tag density variation determined from time to time. In particular, the speed is advantageously varied inversely according to the number of tags detected in a previous scanning section.

This way, if the number of tags tends to increase in a scanning section, the scanning of the antenna slows down while if the number of tags tends to drop, the scanning speed increases. The total scanning time is thus optimized and no risk exists of missing the detection of some of the tags, especially in areas of the container with a higher concentration or density of tags. The scanning speed follows the pattern of the density or concentration of tags in the scanning direction.

In particular, it has been found advantageous that the antenna be moved by steps along the axis 26 and at each step the detectable tags be counted to then use the resulting number to change the movement of the antenna at the next step. In an advantageous way of working, the detection of the tags occurs during a stop time of the antenna between one step and the next. After the detection, the antenna is moved by the next step and the new number of tags is read. The number of tags read at each step changes the length of the following step and/or the stop time between one step and another for the detection of the tags. In particular, the length of each step can be calculated by the control unit to be inversely proportionate to the number of tags detected at the previous step. In addition, or alternatively, the stop time between one step and the next can be calculated in a way directly proportionate to the number of tags detected at the previous step. The proportionality between number of tags and movement speed (as continuous speed or as a result of the length of the step and/or stop time) will depend on the performance of the electronic detection system, meaning the number of tags that can be detected with a high degree of reliability at that speed of movement. This can be calculated or verified experimentally according to the system and set in the control unit. Advantageously, the initial scanning speed is selected the same or below that associable with a reliable reading of an expected maximum number of tags readable in a scanning section of the antenna. For example, if the system is expected to detect at most 100 tags in a scanning section of the antenna (which can also be defined as the axis section 26 along which the antenna reliably detects tags without moving along the axis) in a certain time, the stop time for the first section will be this certain time

(and/or the initial step will be equal to such section) , so as to be certain of detecting all the tags that can be present. In the case of a smaller number of tags in the first section, there will be a waste of time, but such waste will go unobserved with respect to the total scanning time of the entire volume. After the first section the system will in any case adapt to the pattern of the number of tags in the subsequent sections and the time will become optimized.

At this point it is clear how the preset objects have been achieved. It has been found that with a method according to the invention, we have precise and reliable tag reading even in the presence of thousands of tags in the same reading volume. The reading volume can also be very high. Furthermore, the reading of a multitude of tags in a volume equal, for example, to an entire roll-container, can be performed at a high speed. The reading system described here allows the reliable scanning (100% reading rate) of a roll-container in a time below one minute, and therefore absolutely competitive compared to the known systems . The reading chamber which allows scanning more than one roll container at a time further reduces the time needed to process a large number of roll-containers . All this with a procedure that can be automatic or semiautomatic, with minimum labor requirements. With the method and the station according to the invention, the possibility is thus obtained of realizing completely automated identification processes, with the advantages of increasing operating efficiency, thanks to a reduction in the times needed for automatic identification. Furthermore, hygienic problems are avoided, for example in the case in which the contents of the roll container is contaminated and/or infected (e.g. hospital linen), the risks are eliminated of damaging the contents in the case of fragile articles or articles that deteriorate, spoil, etc., and the risks are eliminated of possible injuries in the case of heavy, cumbersome or hard-to-handle articles. Naturally, the above description of an embodiment applying the innovative principles of the present invention is shown by way of example of such innovative principles and must not therefore be considered as limitative of the patent right ambit claimed here. For example, the sliding annular antenna station can be different to how it has been shown to describe the method according to the invention and its parts can be missing or be varied, as easily imaginable by the expert technician in the light of the description given above, also in virtue of the type of articles or article containers to be processed. Entrance and exit buffers can also be envisaged that allow waiting lines to adapt the needs in the arrival and departure times imposed by the rest of the system to the processing time in the station according to the invention. If the container has to be lifted further in the reading chamber, the lift can be of different type, even with double or triple pantograph.

Claims

1. Method for the automatic reading of a plurality of RFID tags in a limited volume, comprising the sliding according to an axis along the volume of a tilted circular antenna that embraces the volume while a relative rotation is applied around said axis between antenna and plurality of tags in the volume, in which the scanning speed of the antenna along the axis is automatically varied according to the density of the tags detected during the scanning.

2. Method according to claim 1, in which the scanning speed of the antenna in a section along the axis is varied inversely according to the number of tags detected in a previous scanning section.

3. Method according to claim 1, in which the antenna is moved in steps along the axis.

4. Method according to claim 2, in which tag detection occurs during a stop time between one step and the next.

5. Method according to claim 2, in which the length of each step is inversely proportionate to the number of tags detected at the previous step.

6. Method according to claim 2, in which the stop time between one step and the next is directly proportionate to the number of tags detected at the previous step.

7. Method according to claim 1, in which the initial scanning speed is chosen the same or less than that associable with a reliable reading of an expected maximum number of tags detectable in a scanning section of the antenna .

8. Station for the automatic reading of a plurality of RFID tags in a limited volume, comprising a tilted circular antenna which is motorized to slide along an axis along the volume to embrace the volume and motorized means for the relative rotation, around said axis, of antenna and plurality of tags in the volume, characterized in that it comprises a control unit which during the scanning commands the change of the scanning speed of the antenna along the axis according to the density of the tags read during the scanning.

9. Station according to claim 8, characterized in that the control unit commands the movement of the antenna with a speed that is varied inversely according to the number of tags detected by the antenna in a previous scanning section.

10. Station according to claim 8, characterized in that the control unit commands the movement of the antenna in successive steps, at each step commanding a change in the stop time between the steps or the length of the step according to the number of tags detected by the antenna in the previous step.

11. Station according to claim 8, characterized in that it comprises a horizontal conveyor (11) for conveying roll- containers from an entrance area (13) to an exit area (14) of the station across a reading chamber (15) in which is present a lifting unit (16) that engages below a roll-container on the conveyor and lifts it to move it vertically away from the conveyor and start it rotating around said axis (26) arranged vertically, in the chamber being present the tilted circular antenna (27) for reading RFID tags and which is motorized to slide vertically to scan the rotating roll-container from top to bottom and read all the tags in the roll-container.

12. Station according to claim 9, characterized in that the horizontal conveyor (11) has guides (20, 21) for the guided accommodation of lower wheels (19) of the roll-container and motorized chains (22) parallel with the guides to engage the roll-container and drag it along the guides from the entrance area to the exit area stopping in said reading chamber .

13. Station according to claim 7, characterized in that the lifting unit (16) comprises a pantograph lift (30) with an upper platform (31) that comprises a horizontal plate (37) motorized to turn around said vertical axis (26) and which is ready for coupling with the bottom of the roll-container.

14. Station according to claim 1, characterized in that the reading chamber (15) has electromagnetic-screen metal walls.