EP2310979A1

EP2310979A1 - Sequence recognition of rfid transponders

Info

Publication number: EP2310979A1
Application number: EP08785389A
Authority: EP
Inventors: Thomas Bleisteiner
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2008-08-06
Filing date: 2008-08-06
Publication date: 2011-04-20
Also published as: WO2010015266A1; CN102112994A

Abstract

The invention relates to a method for detecting the sequence of RFID transponders (T) captured by an RFID reader (L), wherein objects (O) are associated with the RFID transponders (T), wherein the objects (O) are moved past the RFID reader (L) on a conveyor (f), wherein all RFID transponders (T) captured during the movement of the object (O) between two defined points (A, E) of the conveyor (f) are associated with the object (O), wherein a quality value (Q) is determined for the probability that the RFID transponder is present at the object (O) and wherein the association of an RFID transponder (T) to the object (O) is removed if the determined quality value (Q) is less than a previously determined threshold value (Sabs).

Description

description

Sequence recognition of RFID transponders

The invention relates to a method for detecting the order of detected by an RFID reader RFID transponders.

Today, RFID readers for reading RFID transponders are used wherever it is necessary to sort and distribute objects, such as general cargo. Increasingly, such RFID readers are therefore used in baggage sorting or postal distribution centers to ensure rapid sorting and speedy transport of luggage or packages. Here are the transponders, which are applied to the cargo, stored data about its destination. This information is read out of the transponders at certain reading stations via the RFID readers, so that the luggage or packages with the transponders attached to them can be distributed on the basis of the information or passed through the baggage sorting system. Thus, a path decision is made for the corresponding items of luggage or packages on the basis of the data on the RFID transponders.

For the smooth transport process, the correct identification of the order of the piece goods guided through the RFID reading cabin is therefore essential when reading and writing the RFID transponder. Especially with fast-moving and tightly packed general cargo, it is important that the conveyed objects are detected correctly in their order. If this does not happen, it may happen that the cargo is transported in the wrong direction or to a wrong destination. Particularly in the case of baggage handling systems or in mail distribution centers, where speed of transport is important, pieces of luggage or parcels are guided through the RFID reader at high speed and at a suitable distance. It may therefore happen that the RFID reader device simultaneously detects several transponders that belong to different packages or pieces of luggage and thus a unique recognition is lost, so that there is a faulty sorting.

In order to avoid these errors, nowadays particularly shielded reading cabins are used, so that as far as possible only the object located in the cabin is recognized by the RFID reader. In addition, to ensure error-free recognition of the sequence of objects moved one after the other through the cabin, a certain minimum distance must be maintained between the objects, depending on the speed of the objects. However, it is desirable that this distance is reduced and still a secure detection of the RFID transponder and thus a secure assignment of the transponder and thus the RFID reader passing objects is guaranteed.

The object of the present invention is therefore to provide a method which enables a secure order sequence identification of RFID transponders and thus of the objects.

The object is achieved by a method for detecting the order of RFID transponders detected by an RFID reader, in which the RFID transponders are assigned to objects, the objects being moved past the RFID reader on a conveying path during which the movement of an object between two defined points of the conveyor line all detected RFID transponders are assigned to the object, in which for each RFID transponder a quality value for the probability that the RFID transponder is located on the object, and in the the assignment of an RFID transponder to the object is canceled if the determined quality value falls below a first defined threshold value. The invention is based on the finding that a measure for the correct assignment of this corresponding transponder to the object can be given by the formation of a quality value which reflects the frequency of detection of a transponder for a specific object. Here, the quality value is an absolute measure, since it is determined from the sum of the detection of a transponder for a particular object. Each transponder detected in the reading booth by the RFID reader can be assigned a value in this way, and a simple comparison with a given threshold value allows a statement as to how good the detection of the transponder is with respect to the object. The assignment to the object takes place here in a simple manner, in which the detection of the transponder for determining the quality value takes place during a defined period of time, which takes place via the movement of the object on the conveyor belt between a fixed start and a fixed end. It is thus precisely recorded how often the transponder was read in, while the object moves from a defined starting point to a defined end point. A simple assignment of the detection of the transponder to the object is guaranteed.

The calculation of this quality value is simple and can be carried out directly during the transport of the luggage or packages with the appropriate transponders by the RFID reader. Thus, a quality value for the assignment of the transponder to the objects is already determined during the transport.

In this case, the ascertained quality value is preferably determined from the sum of all detections of a transponder. This is a simple rule that leads to a speedy and safe result for the transponder's quality value. Several detections occur when several antennas of the RFID reader arranged in the cabin detect the transponder at the same time, or if the object is the reading cabin in this way durchfährt that the transponder is detected during several scanning cycles of the RFID reader.

An advantageous embodiment of the invention is characterized in that the determined quality value of a first RFID transponder during the movement of the object between the two points with the determined quality value of a subsequent RFID transponder during the movement of the object between the two Points is compared.

In this case, it is made use of in a simple manner that a quality value is determined for each transponder during the passage of an object. This quality value can be compared with the quality value of another transponder which is read during the transit of the object. If, for example, during the movement of an object between the two points (beginning and end) for the measurement, a first transponder is detected four times and a second transponder detected only twice, the quality value of the first transponder is higher than that of the second transponder. If these two are set in relation, the result is a value that serves as a measure of the correct assignment of the transponder to the object. Here, the value is most easily formed from the quotient of the two quality values of the detected transponder. If the quotient exceeds a defined threshold value, the assignment of the first detected transponder to the object is canceled. There is thus an evaluation function for each transponder, which makes it possible to determine whether a transponder belongs to an object. This method or the calculation is carried out until all transponders detected at a time when the object was located between the beginning and the end of the measuring section are compared with one another. As a result, the transponder is then assigned to the object that had the better quality value.

A further advantageous embodiment is characterized in that that for an RFID transponder for a first Ob- jekt quality value is compared with the quality value determined for the same transponder for a subsequent object. With these methods, it is possible cases in which there is still an uncertainty about the assignment of the transponder to the object to assign, characterized in that the quality for the detection of the transponder over several successive objects is determined and compared. Here, the transponder is evaluated for a number of predecessor objects and a number of subordinate objects. This evaluation is done via all transponders which have been assigned to the current object. For example, it is counted how often a first transponder for a first object has been detected. This value is compared to how many times the same transponder has been detected for a subsequent object. In this case, an evaluation function is again defined, which bases on the quotient of the quality of the detection of the first transponder in the current object and the detection of the same transponder in the comparison object. If a defined threshold value is exceeded by the quotient of the evaluation function, the assignment of the checked transponder from the current object is deleted. This evaluation is carried out for all transponders recorded for a current object. This evaluation can also be carried out for all subsequent properties. Overall, in this way, by evaluating the quality of the individual transponders within an object, as well as the quality of a specific transponder over several objects, a reliable determination of the order in which the transponders are moved by the RFID reading unit is ensured.

It is also possible first to compare the quality of a specific transponder over several objects, and then to evaluate the transponders within an object. This is especially relevant if the reception quality of individual consecutive transponders, eg due to unfavorable position of the transponder on the object, strongly fluctuates. For example, would a transponder be read very frequently? and the following very rare, would be assigned by an evaluation of the two transponders, based on an object, the wrong.

The presented method can be used particularly well in environments in which many objects, to which transponders are assigned, are moved past an RFID reader at high speed and in which the information on the transponders is read out to the object as a function of to transport the data read out in a certain direction. The method is thus applicable to any form of single-piece sorting equipment. It is therefore equally applicable to manufacturing plants in which workpieces are to be transported in different ways depending on their property or be processed differently. The method can also be used for the sorting of material or workpieces in high-bay warehouses.

A secure assignment of the objects despite high transport speed and small distance between the objects is ensured by means of the method. This security is set via the quality rating functions and the corresponding thresholds. With the method, random transponder captures of other objects, which result from reflections due to the structural conditions, are reliably filtered out. The comparison of the transponders of different objects leads to an increase in the probability that a transponder is reliably assigned to an object. This is especially noticeable when there are small distances between the objects to be detected.

The invention will be described and explained in more detail below with reference to the figures. Show it:

1 shows a schematic representation of a transport system, FIG 2 is a representation of the method in a flowchart. 1 shows a transport system for objects O, which may be piece goods, such as parcels or items of luggage or workpieces or workpiece carriers. The objects are conveyed on a conveyor line f, in which case they are moved through a reading cabin with an RFID reader L. Each object O is assigned an RFID transponder T. In the reading cabin, the transponders T are detected by the RFID reader L, which has several antennas LG here. Here, the order in which the objects O and thus the transponder T are moved on the conveyor line f, determined. The objects O are then transported on the basis of the ascertained sequence on different paths, for example to two different destinations Z1, Z2.

2 shows a flowchart indicating the steps of the method for sequence detection of RFID transponders.

1st step: Assignment of all recorded transponders within a defined reading range:

While the object O is moving on a conveyor line f, between a defined start and a defined end all detected transponders are assigned to this object 0. The following is defined: f _Λ = start of conveyor area f _E = end of conveyor area

2nd step: Determining the quality of a transponder per object: A quality Q is determined for each transponder T, which establishes a relation to the probability that the transponder T is located at the object:

Q (T ₁ ) = quality of the transponder T ₁ .

In the simple case, the quality is the summation of all detections of the transponder T ₁ :

If Q (T ₁ ) falls below a defined threshold value S, the assignment of transponders to an object is resolved.

3rd step: Evaluation of the transponder for different objects:

After the second step, there are still cases in which there is uncertainty about whether all assigned and evaluated transponders actually belong to the object.

For this purpose, the transponders and their quality are determined in the third step over several successive objects. A rating function B _{01 is} defined, which refers to a specific transponder T ₁ over several objects. In the generalization, this means that the

Transponder T _{1 is} evaluated for m precursor objects and n successor objects. The evaluation is made via all transponders which have been assigned to the current object. Step 3 may begin for a particular object if the n successor objects have left the defined read range of step 1. In the simple case, the evaluation function B _{oi is} the quotient of the quality Ti in the current object 0 _A , and in the comparison object O _v : ^' If one evaluates the comparison object, the result is: a _* (o .. <w,) - Uθy VI}).

Looking at the simple case of quality determination from step 2, the following results for the current object:

For the comparison object:

In the simplest case, this compares only with the predecessor and the successor object.

Step 3.1: An evaluation of a transponder with respect to the predecessor object O _{v takes place} :

If the evaluation function B ₀ (θ _A , O _v , T _l ) exceeds a defined threshold value S with respect to the current object O _A , the transponder T _{1 is} removed from the current object. This evaluation is carried out for all transponders of the current object.

If the evaluation function B _Oy (θ _A , O _v , T _ι ) exceeds a predefined threshold value S with respect to the preceding object, then the transponder T ₁ , from the preceding object, becomes removed. This evaluation is carried out for all transponders of the current object.

Step 3.2: An evaluation of a transponder with respect to the successor object O _{N takes place} :

Exceeds evaluation function B _o ^ (O _A, O, _N, T _t) with respect to the current object O _A, a fixed threshold value S, the transponder T will ± removed from the current object. This evaluation is carried out for all transponders of the current object.

If the evaluation function B _N (θ _A , O _N , T _j ) exceeds a defined threshold value 5 with respect to the subsequent object O _N , then the transponder T ± is removed from the following object. This evaluation is carried out for all transponders of the current object.

4th step: Evaluation of the transponders left over from step 3:

In order to determine whether a transponder actually also belongs to an object, an evaluation function B can finally be defined for each transponder Ti, which evaluates this with respect to a second transponder T _j . If the evaluation function exceeds a specific threshold value S, the transponder Ti is removed.

B _T {Γ ,, T _J ) = evaluation function b with respect to Ti, depending on Tj, B _τ [T ₁ , T _J )> S: Transponder is removed from object Ti.

In the simple case, the evaluation function is the quotient of the quality of T _j and Ti B (TT) - ^Q ^ τ ^λ " ^jh Q (T ₁ )

Considering the simple case of the quality determination from step 2 results:

If the threshold value S is set to two, for example, then the transponder T _{1 is} removed if the number of detections of the transponder T ₃ is higher by more than a factor of two.

Step 2 is ended when all transponders detected at a time are compared with each other.

For the present invention, it is immaterial whether the sequence of the method steps according to the invention described above is maintained exactly. The secure detection of the RFID transponder and thus the moving objects can also be achieved by a method in which, after the first and second step, first the fourth step described above and then only the third step.

Claims

claims

A method for detecting the order of RFID transponders (T) detected by an RFID reader (L), in which the RFID transponders (T) are assigned to objects (O), the objects (0) being located on a conveyor line (f) are moved past the RFID reader (L),

in which during the movement of an object (0) between two defined points (A, E) of the conveying path (f) all detected RFID transponders (T) are assigned to the object (0),

- For each RFID transponder (T) a quality value

(Q) for the probability that the RFID transponder (T) is located on the object (0), and - in which the assignment of an RFID transponder (T) to the object (0) is canceled if the determined quality - Value (Q) falls below a first defined threshold (Sabs).

2. The method of claim 1, wherein the determined quality value (Q) from the sum of all detections of the RFID transponder (T) is formed.

3. The method of claim 1 or 2, wherein the determined quality value (Q) of a first RFID transponder (T) of a first object (0) during the movement of the object (0) between the two points (A, E) is compared with the determined quality value (Q) of a subsequent RFID transponder (T) during the movement of the object (0) between the two points (A, E).

4. The method of claim 3, wherein the quotient of the quality value (Q) of the subsequent RFID transponder (T) and the first RFID transponder (T) is formed.

5. The method of claim 4, wherein the assignment of the first transponder (T) to the object (0) is canceled when the quotient formed exceeds a second set threshold (Srei).

6. The method according to any one of the preceding claims, wherein the for a RFID transponder (T) for a first object (O _A ) determined quality value (Q) with the for the same transponder (T) for a subsequent object ( O _N ) quality value (Q) is compared.

7. The method of claim 6, wherein a quotient of the for the RFID transponder (T) for the first object (O _Ä ) determined quality value (Q) and for the same transponder (T) for the subsequent object (O _N ) determined quality value is formed.

8. The method of claim 7, wherein the assignment of the transponder (T) to the first object (OA) is canceled if the quotient formed exceeds a third predetermined threshold.

A method according to any one of the preceding claims, wherein the objects (0) are pieces of luggage in a baggage handling system.

10. The method according to any one of the preceding claims, wherein the objects (0) are assigned to certain destinations based on the order of the RFID transponder.

11. sorting system for sorting piece goods as objects, with at least one RFID reader for sorting the piece goods with the method according to one of claims 1 to 10.

The sorting system of claim 11, wherein the parcels are parcels in a mail distribution center.

13. A sorting system according to claim 11, wherein the parcels are pieces of luggage in a baggage handling system.