1. Field of the Invention
The present invention relates to an electronic tag and an electronic tag system constituted by an electronic tag and by a reader/writer, and specifically to an RFID tag system comprising devices such as a radio frequency identification (RFID) tag adopting a data transmission/reception via radio, and a reader/writer that transmits and receives data to and from the RFID tag.
2. Description of the Related Art
Electronic tags have been widely used in recent years for product management and the like, by being attached to, for example, a commercial product. Among the commercialized products, there exists a specific RFID tag having a sensor capable of detecting, for example, the temperature, humidity, acceleration, electric resistance, and such, of the environment where the tag is equipped, so that the RFID tag system is capable of performing a process in response to the environment on the basis of the information obtained from such a sensor.
The sensor-equipped RFID tag 1 comprises a sensor 5 for receiving the external information 4, an analog/digital (A/D) converter 6 for converting sensor input data into digital data, a tag LSI control logic circuit 7 for outputting the sensor input data converted to the digital data as response data to the R/W 2 in response to a command from the R/W 2, an RF unit 8 for transmitting and receiving data to and from the R/W 2, and memory 9. Here, the RF unit 8, being constituted by a transmission unit and a reception unit, comprises a rectification circuit for rectifying the alternating current (AC) power given from the outside if the tag is a passive tag receiving a provision of an operating power from the outside. Meanwhile, the configuration is such that the memory 9 in this comprisal is not capable of reading or writing response data from or to the R/W 2 for which the sensor input data is digitized.
Referring to
In
Then the R/W 2 recognizes tags which have sent the data indicating 30° C. and higher from among the pieces of data sent from all tags, and it sends, for example, the sensor data, temperature data, e.g., from a plurality of RFID tags 1 to a host system as a discretionary continuation process, which results in the host system executing a process related to an environment in which the temperature sensor-equipped RFID tag 1 is installed, by way of a temperature control for an air conditioning machine in step S7.
Next is a description of the anti-collision process in detail. In the anti-collision process, although its algorithm is different depending on the standard, what is basically performed is the process for obtaining the respective UIDs of a plurality of RFID tags 1 which have responded back when the responses from the plurality thereof which have responded back as described above collide with one another.
Next is the description of the algorithm by exemplifying the ISO/IEC18000-6 described later. In this process, a group_select command is first transmitted from the R/W 2 as a broadcast (i.e., a broadcast type) command to all RFID tags 1 in step S10. The assumption here is that the group_select command is sent to all the RFID tags existing in the communication zone of the R/W 2 so that the RFID tags 1, having received the command in step S11, transmit the respective UIDs of the tags per se, as the responses, to the R/W 2, for simplicity of description.
In step S12, while the UIDs are transmitted from, for example, all the RFID tags 1 existing within the communication zone, there are generally plural pieces of such tags, and therefore the R/W 2 performs a screening process by detecting the collisions in step S13. In the screening process, what is repeated is that the plural RFID tags which have transmitted the respective UIDs as described above are screened and culled to eventually one RFID tag 1 and that the UID of the one RFID tag 1 is received.
According to the standard specified in the aforementioned ISO/18000-6, for example, the next broadcast command is first sent from the R/W 2 as a screening process. The RFID tags 1, which have transmitted the respective UIDs in step S12, each perform the process of generating, for example, a one-bit random number and transmitting the UID if the value of the random number is “0” while not transmitting the UID if it is “1”. This process reduces the number of tags transmitting the UIDs, that is, sending responses.
If there are plural tags responding in this event, collisions occur again. The R/W 2 accordingly transmits a broadcast command again so that the RFID tags 1 that transmitted the UIDs previously each repeat the process of generating a one-bit random number and transmitting the UID if it is “0”. This process enables the R/W 2 to obtain the UID of one RFID tag 1 as a result of only the aforementioned RFID tag 1, eventually transmitting the UID thereof. After obtaining the UID of one RFID tag 1, a repetition of the similar process from the beginning makes it possible to obtain the respective UIDs of the other RFID tags 1. Note that if the number of RFID tags 1 sending responses suddenly becomes “0” during the above described process, the process returns to the previous for repeating the above described process.
As such, the conventional example shown in
In the actual data collection, it is necessary to judge whether or not the temperature detected by the thermal sensor exceeds a predefined value in order to control, for example, an air conditioner. It is necessary to issue an alarm from a host system and/or to record the clock time in accordance with the result of judging whether or not there is a sensor-equipped RFID tag which has detected a temperature being, for example, no less than 30° C.; and necessary to obtain the respective pieces of sensor data simultaneously for all sensor-equipped RFID tags. Even if it is possible to carry out the processes in, for example, 0.5 seconds, to obtain sensor data from one RFID tag and processing the result of obtaining the data, it takes 100 seconds to obtain, sensor data for 200 tags, thus one is faced with the problem of being unable to obtain data simultaneously.
In reference non-patent document 1, as one of the conventional techniques related to such an RFID tag, the anti-collision process is specified in detail as described above. Meanwhile, in reference non-patent document 2, the characteristics of a 13.56 MHz, CMOS RFID tag having FRAM as ferroelectric memory are described in detail.
The use of such a conventional technique has not been able to solve the problem of being unable to collect the sensor data rapidly from the sensor-equipped RFID tags which have detected, for example, a temperature exceeding no less than a predefined temperature.
An electronic tag according to the present invention comprises a data storage unit for storing transmission-use data converted into digital data; and a tag identifier transmission-necessity judgment unit for comparing between comparison data transmitted from an R/W and data stored in the data storage unit and determining whether or not the identifier of the tag per se is to be transmitted to the R/W in order to participate in an anti-collision process carried out between the electronic tag and R/W as a necessary process prior to transmitting data to the R/W.
Referring to
The tag identifier transmission-necessity judgment unit 14 is for comparing between comparison data transmitted from an R/W, e.g., a threshold value, and data stored in the data storage unit 13 and determining whether or not the identifier of the tag per se is to be transmitted to the R/W in order to participate in an anti-collision process carried out between the electronic tag and R/W as a necessary process prior to transmitting data to the R/W corresponding to the condition shown from the R/W.
Next, the R/W 12 comprises a data-obtainment request transmission unit 15 and a comparison data transmission unit 16. The data-obtainment request transmission unit 15 is for sending a command that requests transmission-use data from the that the electronic tag 11, and the comparison data transmission unit 16 is for sending the comparison data to an electronic tag 11 to be compared with the transmission-use data stored in the data storage unit 13 comprised by an electronic tag 11.
That is, a third preferred embodiment described later is configured to transmit a data-obtainment request, e.g., a sensor reference command, from the R/W 12, and to store, for example, sensor data in the data storage unit 13 comprised by the electronic tag 11 in response to the reception of the aforementioned command.
Then, comparison data, for example a threshold value, is sent from the R/W 12 to the electronic tag 11, so that the electronic tag 11 determines whether or not to participate in an anti-collision process by using the comparison data and, for example, a judgment condition sent simultaneously, and the tag transmits the unique identifier UID of the tag per se if the electronic tag is to participate.
Next, in the electronic tag system corresponding to a first preferred embodiment of the present invention, an electronic tag comprises a threshold value judgment unit for comparing between transmission-use data converted into digital data and a threshold value and for judging whether or not a threshold value judgment condition is satisfied; a data storage unit for storing the transmission-use data if the judgment condition is satisfied; and a tag-identifier transmission unit for transmitting the identifier of the tag per se in order to participate in an anti-collision process carried out between the electronic tag and the R/W as a necessary process prior to transmitting data to the R/W if the judgment condition is satisfied.
Corresponding to the above described configuration, the R/W is equipped with a data-obtainment request transmission unit similar to the configuration shown in
Furthermore, in the electronic tag system corresponding to a second preferred embodiment of the present invention, an electronic tag comprises a threshold value judgment unit and a data storage unit, which are similar to the first embodiment, and further comprises a tag identifier transmission-necessity judgment unit for determining whether or not the identifier of the tag per se is to be transmitted in order to participate in an anti-collision process as necessary prior to transmitting data, as in the above description, in accordance with a condition sent from the R/W after the data is stored.
The R/W is equipped with a data-obtainment request transmission unit similar to the above described configuration and additionally equipped with a judgment-request transmission unit for sending the condition data necessary for the electronic tag to determine the presence or absence of a need to participate in the above described anti-collision process so that the electronic tag judges a threshold value at the time of receiving, for example, a sensor reference command in the same manner as the above description and, if the judgment condition is satisfied, writes the transmission data to the memory; thereafter followed by determining the need or not of participating in the anti-collision process at the same time as receiving the above described condition data as, for example, a group_select command and transmitting the unique identifier UID to the R/W if participating in the anti-collision process.
Such is the description of the outline of the present invention. The following is the description of the preferred embodiments of the present invention in detail, described by using the drawings of the system configuration, tag configuration, and a sensor data collection process sequence.
The R/W 2, comprising an antenna 17, a transmission/reception unit 18 and a control unit 19, is connected to a computer or a backend system 20 as a host system, with, for example, the computer 20 being connected to a database 22 by way of a network 21.
Note that although the sensor 5 and A/D converter 6 are comprised within the RFID tag in
In the sensor reference process and response process of S17, first a sensor reference command from the R/W (R/W) 2 is transmitted to, for example, all RFID tags 1 within the communication range as a broadcast command.
At the RFID tags 1, each of the RFID tags 1 possessing the respective unique UIDs, e.g., UID0, UID1, UID2 and so on, receives the sensor reference command in S21, refers to each respective sensor, A/D-converts the sensor data in S22, compares them with the threshold value in S23, writes the data to the memory in S24 if the sensor data satisfies the judgment condition (such as that the data is larger or smaller than the threshold value), and transmits the unique identifier UID of each respective tag per se to the R/W 2 in S25. If the judgment condition is not satisfied as a result of judging the threshold value in S23, the RFID tag 1 possessing, for example, UID2 does not perform the memory writing in S24 or the UID transmission in S25, and instead ends the substantial process in S23.
In the anti-collision process carried out in the subsequent S18, collision detection and a screening process are carried out if the UIDs are transmitted from a plurality of RFID tags 1 in S25. This process is similar to the process according to the conventional example described for
Note that the configuration described here ends the sensor data collection process when the UID recognition process for RFID tags is completed; it is of course possible to send, thereafter, a common command for reading from R/W 2 the content of the memory of the RFID tags 1 that have transmitted the respective UIDs in a similar manner as the conventional example of
As described above, the present embodiment is configured to compare the sensor data with the threshold value stored in, for example, the specific address of the memory and also to write the data to the memory if the judgment condition is satisfied. It is also configured so that only the RFID tags 1 which have written the respective pieces of sensor data to the memory participate in the anti-collision process by those RFID tags 1 sending the respective UIDs.
For example, if the sensor data is temperature data and if the memory is written in the case of the temperature being no less than 30° C., a conversion of such sensor data into digital data easily comparable with the threshold value when the sensor data is converted into digital data makes the judgment process easy. In an example case of converting the temperature data between −40° C. and 87.5° C. into 8-bit digital data, setting, for example, a quantization step to 0.5° C. expresses the temperature data of 30° C. as hexadecimal data “8C”. The use of the hexadecimal data “8C” as a threshold value causes only the sensor-equipped RFID tags detecting the temperatures with values no less than 30° C. to participate in the anti-collision process. Further, in order to detect the existence of the sensor-equipped RFID tags detecting, for example, the temperatures being no less than 35° C., the use of hexadecimal data “96” as the threshold value enables a threshold value judgment.
As such, in the first embodiment since only the RFID tags storing temperature data with a value no less than 30° C. designated as the threshold value in the memory is returned, it possible to screen only the RFID tags with values no less than 30° C. as the target and also possible to obtain at a high speed the UIDs of the RFID tags respectively storing the sensor data indicating no less than 30° C. which the R/W desires to know. This high speed process capability is obtained by making a RFID tag that obtains the sensor data with a value less than 30° C. not participate in the RFID tag anti-collision process. At the R/W, it is possible to know how many RFID tags storing the respective pieces of sensor data with a value no less than 30° C. there are in the memory, or it is possible to know in which positions the RFID tags with data values no less than 30° C. exist, as a result of the process in S19, and thereby the data can be reflected to, for example, controlling an air conditioner. As described above, the process sequence shown in
Note that the memory 9 shown in
The next one-byte is a threshold value storage address which is used for a threshold value judgment by reading the threshold value stored in the aforementioned address of the memory 9 in
First, a sensor reference command from the R/W is received in S21, a threshold value used for a threshold value judgment is read from, for example, the address designated by the command of
The electric resistance detection sensor 25, being a sensor for detecting the electric resistance between sensor input terminals, is for sensing one-bit information to determine whether the input terminals are mutually short-circuited or open. Because the sensor input information is one-bit, the judgment of a threshold value is not required; therefore, the tag LSI control logic circuit 7, upon receiving a sensor reference command from the R/W, initiates the sensor 25, writes a detection flag to the memory 9, transmits the UID of the tag per se, and participates in an anti-collision process thereafter if the input terminals are mutually open. If the input terminals are mutually short-circuited, the tag LSI control logic circuit 7 does not write a memory detection flag to the memory 9, shifting the present tag to the state of no-response and additionally not participating in the anti-collision thereafter.
At the R/W, if a collision among the UID responses to the sensor reference command does not occur, it is possible to identify an RFID tag in which the sensor terminals are mutually open. If a collision among the UID responses occurs, performing the screening process in a similar manner as
Next, while volatile memory, such as static random access memory (SRAM), can be used as, for example, the memory 9 shown in
In the sensor reference process of S27 shown in
In the anti-collision process of S28 shown in
If the UID transmissions from a plurality of RFID tags 1 collide with one another, a screening process as an anti-collision process is carried out in steps S13 and S14 in a similar manner to the above description, and a recognition process for the UID of a tag(s), in which the sensor data is within a specific range, is carried out by the R/W 2 in S19 and then the process ends.
Incidentally, while the correlation of
The configuration of the sensor-equipped RFID tag in the second embodiment is the same as that shown in
Further in
Note that, if the respective pieces of sensor data sent from a plurality of sensors are stored in the respectively corresponding addresses within the memory as described above, the designation of a storage address within the memory of the sensor data as a target, in, for example, a group_select command possessing a format similar to
Lastly, a description is provided for a third preferred embodiment.
That is, the third embodiment is configured to perform the process of transmitting, as a group_select command, a command including a threshold value after the data is written to the memory at each tag in response to the reception of a sensor reference command, of comparing the data stored in the memory with the threshold value, and of transmitting the UID (s) of the tag(s) from only the tag(s) in which the data satisfying the threshold value judgment condition is written to the memory.
In the sensor reference process of S34 shown in
In the anti-collision process carried out in the subsequent S35, a group_select command is sent as a broadcast command from the R/W 2 to all RFID tags 1 within the communication range in S30, so that the each of the RFID tags 1 receive the command in S31 and only the RFID tags(s) 1 in which the threshold value written to the memory designated by the command, e.g., the temperature data, for example, no less than 30° C., transmits the UID of the tag(s) per se to the R/W 2 in S32. The tag in which the temperature data written to the memory is less than 30° C., that is, the tag 1 possessing the identifier UID2 in this example, will never respond to the group_select command. Here, the group_select command has a format similar to
If there are plural RFID tags 1 which have transmitted the respective UIDs in S32, a screening process as the anti-collision process is carried out in steps S13 and S14; a recognition process for the UID(s) of a tag(s), in which the sensor data is within a specific range, is carried out by the R/W 2 in S19, followed by a data collection process being carried out by using a read command in S36 if specific temperature data of individual tag is required; and the process ends.
Note that the correlation between both
As described above, the present invention is contrived such that, for example, each RFID tag compares sensor data with a threshold value and writes the sensor data to memory if a threshold value judgment condition is satisfied, and such that only the RFID tags which have written the respective pieces of data to the memory send the respective UIDs of the tags to the R/W, thereby enabling the R/W to know the UIDs of the RFID tags in which the respective pieces of data satisfying the judgment condition are stored in the memory. Further, the use of the FRAM as memory for storing the data makes it possible to speed up the process. For example, if only ten pieces of tags, among 200 pieces thereof, obtain the sensor data indicating temperatures being no less than 30° C., the number of tags participating in an anti-collision process is reduced, thus reducing the process time to 5 seconds or less as compared to the total of 100 seconds for processing 200 pieces of tags at 0.5 seconds or less per tag.
This application is a continuation application of international PCT application No. PCT/JP2005/020726 filed on Nov. 11, 2005.
Number | Date | Country | |
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Parent | PCT/JP2005/020726 | Nov 2005 | US |
Child | 12118402 | US |