1. Field of Invention
The present invention relates to a radio frequency identification (RFID) system. More particularly, the present invention relates to an RFID monitoring system and method which can control the electrical power supplying of an RFID tag.
2. Description of Related Art
Radio frequency identification (RFID) is a non-contact automatic identification technique, which automatically identifies targets and obtains relative information by radio frequency signals, so as to have a fast and convenient process, omit manual operations during identifying and be able to identify plural tags and even dynamic targets simultaneously.
A complete RFID system comprises two parts, a reader and a transponder. The transponder is generally called an RFID tag. The operational principle of the RFID system is to transmit radio frequency energy of a certain frequency to the transponder for driving it to transmit its tag ID code, or alternatively, to transmit the tag ID code by the transponder itself. The reader receives the tag ID code and transmits it to a central system for carrying out relative data processes.
Because the electrical power for the RFID tag to transmit the tag ID code is converted from radio frequency energy transmitted by the reader, the RFID tag is called a passive RFID tag. The signal transmission range of the passive RFID tag is too short, and the signal intensity of the same is weak. Alternatively, a power supply can be configured in the RFID tag for continuously supplying electrical power to transmit the tag ID code. This RFID tag, which has a built-in power supply, is called an active RFID tag. The active RFID tag continuously transmits the tag ID code while it approaches the reader, and therefore it overly consumes electrical power such that its attached power supply can not support a long lifespan.
Modern RFID applications include logistics and supply management, manufacture and assemblage, airport baggage service, mail and express delivery, file tracking and library management, animal identification, access control, electrical entrance tickets and automatic fare collection. However, the so-called access control is only to obtain and identify the tag ID code of the RFID tag along with the user by the reader, without the function of tracking or recording the route of the user moving within a certain region.
It is therefore a objective of the present invention to provide a radio frequency identification (RFID) monitoring method to search a RFID tag in a region.
The present invention provides a radio frequency identification (RFID) monitoring method, a reader located in a region to receive a tag ID code from a RFID tag, wherein the method comprises the steps of: (a) sending out a first reading signal from the reader; (b) determining whether the tag ID code is received by the reader, wherein the RFID tag sends out the tag ID code when the RFID tag receives the first reading signal; (c) recording a position of the RFID tag in a plane when the tag ID code is received by the reader; (d) rotating the reader a second angle toward a direction perpendicular to the plane; (e) sending out a second reading signal from the reader; (f) determining whether the tag ID code is received by the reader, wherein the RFID tag sends out the tag ID code when the RFID tag receives the second reading signal; and (g) recording a position of the RFID tag in the direction when the tag ID code is received by the reader.
According to an embodiment, the RFID tag comprises: an antenna arranged to receive an enable signal or a disable signal; a control circuit electrically connected to the antenna; a power supply arranged to provide electrical power to the control circuit for transmitting a tag ID code through the antenna; and a lock circuit electrically connected to the power supply, wherein the lock circuit is arranged to enable and disable the power supply according to the enable signal and the disable signal, respectively.
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
The present invention adds a lock circuit into an active RFID tag for controlling the switching of a power supply of the active RFID tag. By cooperating with an enable signal or a disable signal transmitted from a central controller through a reader, the monitoring capacity of the RFID system within a certain region is enhanced, and the power consumption of the active RFID tag is decreased, thus extending its battery life.
In the first preferred embodiment, after receiving the enable signal or the disable signal transmitted from the antenna 112, the control circuit 114 notifies the lock circuit 118 to enable or disable the power supply 116. Alternatively, the antenna can directly transmit the enable signal or the disable signal to the lock circuit 108. In addition, the control circuit 114 and the lock circuit 118 can be simultaneously integrated into a single controller.
Moreover, the RFID tag 110 further comprises a power converter 119. The power converter 119 converts a signal that is received by the antenna 112 into an electrical power for the control circuit 114 to transmit the tag ID code through the antenna 112. In other words, the RFID tag concurrently has the functions of the active RFID tag and the passive RFID tag. Furthermore, after the power supply 116 is enabled for a predetermined period, the lock circuit 118 automatically cuts off the power supplying of the power supply 116, thus improving the power saving of the RFID tag 110.
When the tag ID code is the same as the assigned code, one of the readers 120a, 120b, 120c and 120d, such as the one which is closest to the RFID tag 110, transmits an enable signal to enable the power supply 116 of the RFID tag 110. The central controller 130, such as a server or other suitable controller, identifies the position of the RFID tag 110 within the region 140 by receiving the tag ID code through the readers 120a, 120b, 120c and 120d. In this embodiment, four readers 120a, 120b, 120c and 120d are used to identify the position of the RFID tag. However, in another embodiment, the position of the RFID tag is identified by a rotatable reader only.
In an embodiment, the reader 501 is located in a corner of the region 500 in
In another embodiment, the motor (not shown in the figure) is disposed in the bottom of the antenna 502 to only rotate the antenna 502 to scan the region 500. That is, the reader body 503 is fixed in a position. When a search is performed by the reader 501, only the antenna 502 is rotated to scan the region 500 to search the RFID tag 504. For example, the reader 501 starts from the Y axle. At this time, the antenna 502 issues a reading signal to scan the region around the Y-axle. If the antenna 502 does not receive any information from the RFID tag 504 after a predetermined time period, such as 5 seconds, that means the RFID tag 504 does not located in this region around the Y-axle, the motor rotates the antenna 502 toward X-axle a predetermined angle, such as five degrees, to process a new search. In this embodiment, the motor rotates the antenna 502 five degrees each time until the RFID tag 504 is identified in the XY plane. After the position of the RFID tag 504 in the XY plane is identified, the motor can rotate the antenna 502 toward the Z axle direction to search the position of the RFID tag 504 in the Z axle.
In step 901, the antenna 502 of the reader 501 issues a reading signal to search the RFID tag 504. Next, a determining step is performed in step 902. The step 902 is to determine whether a tag ID code of the RFID tag 504 is received by the reader 501 or not. In an embodiment, when the RFID tag 504 receives the reading signal from the antenna 502 of the reader 501, the RFID tag 504 can send a tag ID code to the reader 501.
The step 904 and step 901 are performed when the antenna 502 of the reader 501 does not receive the tag ID code. In step 904, a motor rotates the reader 501 a special angle toward x-axle (or y-axle). Then, the antenna 502 of the reader 501 sends out a reading signal again in step 901 to process a new search.
On the other hand, the step 903 is performed when the antenna 502 of the reader 501 receives the tag ID code in step 902. In step 903, the position of the RFID tag in XY-plane is recorded when the reader receives the tag ID code. As shown in the
Next, the reader rotates a special angle toward Z-axle in step 905 and sends out a reading signal in step 906. As shown in the
Then, a determining step is performed in step 907. The step is to determine whether a tag ID code is received by the reader or not. The step 905 and step 906 are performed again when the antenna 502 of the reader 501 does not receive the tag ID code. In step 905, a motor rotates the reader 501 a special angle toward z-axle. Then, the antenna 502 of the reader 501 sends out a reading signal again in step 906 to process a new search.
On the other hand, the step 908 is performed when the antenna 502 of the reader 501 receives the tag ID code in step 907. In step 908, the position of the RFID tag in z-axle is recorded when the reader receives the tag ID code. As shown in the
Finally, the flow chard is performed again when another RFID tag into the region 800.
The preferred embodiment firstly configures the readers 120a, 120b, 120c and 120d on different positions within the region 140 for receiving the tag ID code of the RFID tag 110 (step 202). When one of the readers 120a, 120b, 120c and 120d receives the tag ID code (step 204), the tag ID code is compared to an assigned ID code, determining whether the tag ID code is the same as the assigned ID code (step 206). When the tag ID code is the same as the assigned ID code, the power supply 116 is enabled to provide electrical power for repeatedly sending the tag ID code (step 208). Then, the position of the RFID tag 110 within the region 140 is identified by receiving the tag ID code through the readers 120a, 120b, 120c and 120d (step 212).
Generally, the reader has a preferred available region due to the distance limitation of radio frequency transmission. As illustrated in
For example, when a plurality of RFID tags 110 exist in the region 140, a wanted RFID tag 110 can be firstly assigned. When the wanted RFID tag 110 approaches one of the readers 120a, 120b, 120c and 120d, the power supply 116 of the RFID tag 110 is enabled to make the RFID tag 110 continuously transmit its tag ID code. Moreover, because the power supply 116 generally supplies a greater amount of electrical power than that induced by the power converter 119, the tag ID code therefore can be transmitted to a farther distance by electrical power provided from the power supply 116, thus increasing the possibility of successfully detecting the tag ID code by the readers 120a, 120b, 120c and 120d.
The RFID tag can be disposed on a movable object, such as a user, a portable electronic device, a book, or other object that may be taken by a user and moved along with the user. Therefore, with continuously detecting the tag ID code by the readers 120a, 120b, 120c and 120d that are separately in charge of different subregions 152, 154, 156 and 158, a real-time position of the wanted RFID tag 110 within the region 140 can be instantly identified.
Moreover, the different spatial positions of the readers and the different transmission ranges of the RFID tag can be further used to estimate a more precise position of the RFID tag 110. As mentioned above, the transmission range of the tag ID code can be adjusted by the different amounts of electrical power supplied for transmitting the tag ID code. For example, the transmission region of the tag ID code can be adjusted by different amounts of electrical power from the power supply 116 and the power converter 119, or by different amounts of electrical power supplied from the power supply 116 due to different enable signals.
According to the second preferred embodiment of the present invention, the readers 120a, 120b, 120c and 120d can be suitably disposed spatially within the region 140. The central controller 130 uses the spatial distribution of the readers 120a, 120b, 120c and 120d and the different amounts of power supplying to estimate a more precise position of the RFID tag 110 within the region 140 according to the corresponding variations of which readers can receive the tag ID code under the different amounts of power supplying.
In another aspect, the coverage of each of the subregions 152, 154, 156 and 158 is respectively determined by the signal transmission capacity of each of the readers 120a, 120b, 120c and 120d. Therefore, the coverage of each subregion 152, 154, 156 or 158 can be substantially enlarged by properly adjusting the power and the radio frequency of the corresponding reader. In addition to distributing the readers in a region with an arrangement, such as in a cellular distribution, the RFID monitoring system 100 can be used to monitor the RFID tags within an extensive region, such as within a town or a science park having many factories, rather than only within a restricted area or a single factory.
For clarity, the following descriptions are made with references to
When the power supply 116 is not enabled, an enable signal is transmitted to the RFID tag 110, making the lock circuit 118 enable the power supply 116 to provide electrical power (step 312). When the power supply 116 is enabled, the enable signal is not transmitted (step 314). The position of the RFID tag 110 within the region 140 is identified by receiving the tag ID code through the readers 120a, 120b, 120c and 120d (step 316). Whether the position of the tag ID code (i.e. the RFID tag 110) within the region 140 is identified or not is then determined (step 317). When the position of the RFID tag 110 within the region 140 is identified, a disable signal is transmitted to the RFID tag 110 to make the lock circuit 118 disable the power supply 116 from providing electrical power, saving the power consumption of the power supply 116 (step 318).
The determining step 317 can be based on time; for example, the position of the identified RFID tag 110 can be directly decided after transmitting the enable signal for a few minutes, or after the RFID tag 110 has remained on or around a certain position for a period. Alternatively, this determining step 317 can use other criteria, such as an indication from the system administrator or from the user to whom the RFID tag belongs. The preferred embodiment does not limit the determining manner, and any other manners suitable for different situations should be included in the scope of the present invention.
More precisely, when an object on which the RFID tag 110 is configured has stopped moving or stayed in one of the subregions 152, 154, 156 and 158 for a period, or the object configuring the RFID tag 110 has passed by or entered into one of the subregions 152, 154, 156 and 158, or the system administrator believes the monitoring is completed, the enable can be transmitted to disable the power supply 116 from unnecessary power consumption.
For clarity, the following descriptions are made with references to
The system administrator preferably sets or changes the assigned ID code by the central controller 130, thus enhancing the management flexibility of the RFID monitoring system. However, persons skilled in the art should understand that other manners for setting the assigned ID code, such as separately inputting into each reader or recording in the readers in advance, also fall within the scope of the present invention.
When one of the readers 120a, 120b, 120c and 120d receives the tag ID code (step 404), the tag ID code is compared to an assigned ID code, determining whether the tag ID code is the same as the assigned ID code (step 406). When the tag ID code is the same as the assigned ID code, the power supply 116 is enabled to provide electrical power for repeatedly sending the tag ID code (step 408). Then, the position of the RFID tag 110 within the region 140 is identified by receiving the tag ID code through the readers 120a, 120b, 120c and 120d (step 412). Moreover, the central controller 130 can identify the route of the RFID tag 110 moving within the region 140 by continuously receiving the tag ID code through the readers 120a, 120b, 120c and 120d (step 414).
In addition, in order to achieve the objectives of automatic recording, tracking or controlling, the enable signal can be transmitted to enable the power supply 116 for providing electrical power when the RFID tag 110 initially enters the region 140 (step 413). For example, the reader 120a, which is closest to an entry 142 of the region 140, is used to be an initial reader, which instantly transmits the enable signal to enable the power supply 116 when any RFID tag 110 enters the region 140 through the entry 142. The central controller 130 is ensured to fully record and track the position or route of every RFID tag 110 within the region 140.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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94106851 | Mar 2005 | TW | national |
This application is a continuation-in-part of U.S. application Ser. No. 11/226,229, filed Sep. 15, 2005, which is herein incorporated by reference.
Number | Date | Country | |
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Parent | 11226229 | Sep 2005 | US |
Child | 12553992 | US |