JP2008176697A - Process management system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process management system accurately managing history of completion of each process by reading information about a tag attached on a product in the process with high accuracy by a reader/writer device provided in each of the process, in a line having narrow process intervals. <P>SOLUTION: This process management system has: a tag attached on an article, and identified in association with the article; antennas provided in each the production process, transmitting a read signal to the tag, and receiving a response signal including identification information from the tag in response to the read signal; a transmission part generating the read signal; a reception part detecting a reception level from the response signal; a changeover part switching connection between the antenna, and the transmission part and the reception part; a decision part deciding the presence of the article in the process by comparison between the reception level and a prescribed reference value; and a management part associating the production process with the article in the process based on a decision result thereof to manage a history of the production process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, an RFID tag (hereinafter referred to as “tag”) attached to an article or the like is accessed from an RFID reader / writer (hereinafter referred to as “reader / writer”), the registration information is read, and the article or the like is managed. The present invention relates to a process management system using a Radio Frequency IDentification) system. Especially suitable for process management (for example, manufacturing process management of products assembled on the conveyor system such as a belt conveyor) The present invention relates to a process management system.

  As an application example of RFID system to process management, for example, there is one described in Patent Document 1. There, production management of information device products such as PDA (Personal Digital Assistance) and mobile phones is described. These products are shipped through a series of production processes of “assembly process → software writing process → function confirmation process → shipment inspection process → packaging process”. By recording the process end information on a tag attached to the product every time each process is completed, it is possible to confirm that each process is being performed reliably. In this case, a reader / writer is arranged for each process, and each time the process is completed, information on the completion of the process is written in the tag. Such a case is suitable for managing a large process (a process at a higher level such as an assembly process or an inspection process), and it can be said that the time during which a product stays in one process is relatively long. Writing data to a tag generally requires more time than reading tag information. However, when the time for which the product stays in each process (or the time for passing through each process) is long as in this case, data can be written reliably.

Japanese Patent Laying-Open No. 2006-76724 (FIG. 1)

  By the way, in the process management, there are cases where processes at lower levels (for example, each detailed assembly step in the assembly process) are managed. In such a case, the residence of each process is short, and the area where the process is performed is often narrow. However, in the product transfer system such as the above example described in Patent Document 1, history management is performed by writing to tag information. Therefore, in a system with a narrow process interval or a system with a high transfer speed, the residence time of each process Becomes shorter, a write error occurs, and the history management cannot be performed reliably.

  On the other hand, instead of performing history management by writing to the tag of process completion, it is also possible to read the tag information attached to the product when there is a product in each process and manage the history on the system side such as a computer It is. Specifically, the history management of how far the process has been completed is performed by reading the tag information affixed to the flowed product with a reader / writer provided in each process.

  However, even in this case, when the antenna directivity characteristic of the reader / writer is wide, tag information existing in an adjacent process may be read, and a history management error may occur. In particular, in a process management system in the FA field, it is necessary to manage as finely as possible by minimizing the distance between adjacent processes. In such a case where the interval between each process is narrow, if the reader / writer antenna is also reduced in size, the directivity is further expanded, and the above problem of reading the tag in the adjacent process becomes prominent.

  Therefore, the present invention has been made to solve the above-described problems, and even when the process interval is narrow, the reader / writer device provided in each process sticks to the product that has flowed through the process. It is an object of the present invention to provide a new process management system capable of performing history management as to how many processes have been completed by reading the tag information.

  The process management system according to claim 1 is a process management system that manages a history of each production process that is sequentially performed on an article, the tag that is attached to the article and identified in association with the article, and the production process An antenna that is provided every time, transmits a read signal toward the tag, receives a response signal including identification information from the tag in response to the read signal, a transmitter that generates the read signal, and the response signal A receiving unit that detects a reception level from the receiver, a switching unit that switches connection between the antenna and the transmitting unit and the receiving unit, and the presence / absence of an article in the process by comparing the reception level with a predetermined reference value And a management unit that manages production process history by associating each production process with an article existing in the process based on the determination result.

  Further, in the process management system according to claim 2, the switching unit sequentially switches the antenna provided in each production process along the flow of the process, and the receiving unit receives the reception level of the response signal received by each antenna. Are sequentially detected, and the discriminator is provided in the subsequent process when the reception level by the antenna provided in the previous process exceeds the reference value in the adjacent two processes (referred to as the previous process and the subsequent process). When the reception level by the antenna exceeds a reference value, it is determined that there is an article in a subsequent process.

  As described above, according to the process management system of the first aspect of the present invention, the antenna information installed in each process is sequentially switched to read the tag information of the tag attached to the product existing in each process. When the reception level of the read signal exceeds a predetermined reference value, it is determined that there is a product in the process, so reading errors from the product existing in the adjacent process can be eliminated, and the process management can be performed. There is an effect that it can be performed accurately.

  According to the process management system of claim 2 of the present invention, when the presence of the product in the process is determined, the tag information is again detected by the reader / writer device in the previous process after the product has moved to the subsequent process in the adjacent two processes. Is detected (when the reception level exceeds the reference value), a hysteresis characteristic that determines that the product does not exist in the previous process is provided, so even when the reception characteristic of the reader / writer device is subject to fluctuations due to fading, etc. There is an effect that the process management can be performed more accurately.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below. FIG. 1 is a configuration diagram of a process management system using the RFID system according to the first embodiment. Here, the process management in the case where four production processes (processes 1 to 4) are sequentially performed on the product 21 will be described as an example. In the figure, reference numerals 11 to 14 denote process areas where the processes 1 to 4 are performed. The product 21 is processed in each step in the order of “step 1 → step 2 → step 3 → step 4”. The product 21 sequentially flows through each process by a conveying device such as a belt conveyor, and a predetermined production process (assembly, inspection, etc.) is performed in each process.

  Reference numeral 22 denotes a tag attached to the product 21, and ID information (a code assigned to each tag such as TAG1, TAG2, etc.) for identifying the tag in an internal memory. In this specification, tag information, registration information, product identification (Also called information) is stored. This ID (IDentification) information is different for each tag. When the tag is affixed to the product, the product and the tag are associated one-to-one, and the ID information becomes product identification information. The tag incorporates necessary electronic circuit elements such as an antenna element for transmitting / receiving an RF signal to / from a reader / writer (to be described later), a memory for storing tag information, and a transmission / reception circuit. 31 to 34 are antenna devices having directivity characteristics for transmitting and receiving RF signals to and from the tag 22, and at least one antenna device is disposed for each process area. Each antenna device is arranged such that the antenna direction and the distance from the product conveyance device are determined so as to cover each process area within the beam width (range of the angle θa indicated by an alternate long and short dash line in the drawing). In this figure, an antenna is arranged in the center of each process area so as to face the moving direction of the product. The directivity characteristic of the antenna has a peak in the front direction and has a substantially symmetrical characteristic.

  Reference numeral 40 denotes a reader / writer device, which exchanges RF signals with the antenna devices 31 to 34. As will be described later, in the reader / writer, the connection between the transmission / reception unit for generating and receiving RF signals and the baseband unit following the RF signal and the antenna device is sequentially switched. The antenna device can be controlled. Reference numeral 50 denotes a signal processor for sending process parameters necessary for ID information determination processing to the reader / writer device, receiving ID information from the reader / writer device, and performing application processing for history management of the production process. A general-purpose computer such as a PC (Personal Computer) is used.

  FIG. 2 is a configuration diagram of the reader / writer device. In the figure, reference numeral 42 denotes a time division control switch for sequentially switching the connection between the antennas 31 to 34 and the RF unit 41. The switching time interval can be changed according to the application situation of the system, but the ID is at least once within the time that the product passes through one process (“process passing time”, the time when the product exists in the process). Since reading of information is necessary, switching in a time sufficiently shorter than the process passing time is necessary. In the case of the FA process management system as in the present invention, switching is performed on the order of several tens of ms. Reference numeral 43 denotes a transmission unit that generates an RF transmission signal. This transmitter uses a local signal from a local signal transmitter 45 (abbreviated as “local oscillator”) to modulate and output tag command data, which is a baseband signal, and outputs the modulated signal as high-frequency power. It comprises a power amplifier 432 that amplifies and outputs an RF transmission signal. The RF transmission signal is transmitted to the antennas 31 to 34 via the circulator 46 and the time division control switch 42.

  Reference numeral 44 denotes a reception unit that performs reception processing of an RF reception signal. This receiving unit amplifies the RF received signal from the circulator 46 and outputs it, a demodulating unit 442 that demodulates and generates demodulated data as a baseband signal using the local signal, and the intensity of the received signal. It comprises a level detector 443 that generates a received signal strength indicator (RSSI) signal.

  45 is a local signal transmitter. 47 is a baseband part. 471 is a command data generation unit that generates a reading instruction command for a tag, 472 is a tag ID recognition unit that recognizes ID information of the read tag, and 473 determines whether there is a tag in the selected process area. The determination unit 474 is a switch control unit that controls switching of the time division control switch 42. Reference numeral 50 denotes a signal processing unit. Reference numeral 501 denotes a process parameter setting unit that sends out various process parameters for operation control of the reader / writer device. The process parameters include the moving direction and moving speed of the transport system (conveyor), a reference value that serves as a threshold for reception level determination, and the like. Reference numeral 502 denotes a history management unit that receives tag ID information from the reader / writer device and manages the history of production processes.

  Next, the operation of the process management system using this RFID system will be described. FIG. 3 is an example of a flowchart of FA process management using the RFID system. (A) is a system flowchart of the whole process management, (b) is a detailed flowchart of the tag information reading step (S4). In the process management system of this example, the antenna switching is performed in the same manner as in the product process flow: “process 1 (ANT1) → process 2 (ANT2) → process 3 (ANT3) → process 4 (ANT4) → process 1 ( ANT1) → step 2 (ANT2) →... ”Is assumed to be cyclically switched at regular time intervals. When the system is started, the process parameters are initialized in the reader / writer 40 by the signal processor 50 (S1). Thereafter, the end of the system is constantly monitored (S2). As an operation of the reader / writer, the antenna 31 (ANT1) in the first process 1 is first selected. Based on the control command from the switch control unit 474, the time division control switch 42 connects the RF unit 41 to the antenna 31 (S3).

  Next, read processing of tag ID information in the selected process 1 area is performed (S4). The read signal generated by the tag command generation unit 471 is modulated and amplified by the transmission unit 43 to become an RF signal, and is radiated as a read radio wave signal from the antenna 31 to the process 1 area via the circulator 46 and the time division control switch 42. Then, the tag is accessed (S41). This is performed for a fixed time until switching to the next antenna (S5).

  Here, the characteristics of the antenna device according to the present invention will be described. FIG. 4 is an explanatory diagram of directivity characteristics of the antenna device. As a reader / writer antenna, a planar patch antenna is often used to reduce the size and thickness. As shown in the figure, side lobes are generally generated on both sides of the main beam. The beam width of the antenna device is generally defined by the half-value width of the main beam directivity (the antenna directivity region where the power value is ½ of the maximum value). In the figure, this beam width is indicated by θa. The distance between the antenna and the position in the process area of the antenna arranged in each process area is determined so that the process area is covered within the antenna beam width. The end portions and side lobe portions of the main lobe cover the adjacent process areas. As a result, if the received signal from the tag is not cut off using a reference value level to be described later, the tag information is read by the antenna device in the process area even for a product in the adjacent process area. As a result, a reading error occurs.

  The reading of tag ID information will be further described. If a product exists in the process area, a tag attached to the product responds to the read signal and sends out ID information. This ID information is read by a reader / writer. The ID information is processed by the receiving unit 44 via the antenna device, the time division control switch, and the circulator. The receiving unit performs demodulation of tag information (demodulation unit 442) and detection of a reception level of the RF signal (level detection unit 443) from the RF signal (S42).

  Next, the reception level is compared with a preset reference value (S43). If the reception level is higher than the reference value, it is determined that there is a product in the process area. If the reception level is lower than the reference value, it is determined that there is a product outside the process area. The determination result is sent to the signal processor 50 together with the tag information, and managed by the history management unit 502 (S44).

  The tag is read by the antenna for a predetermined time until the next switching (S45). The switching time of the antenna is generally several tens of ms. On the other hand, the time for access processing to the tag (reading from the tag → response from the tag) is sufficiently shorter than the switching time (on the order of several ms on average). . Therefore, within a time when one antenna is selected, the tag is accessed several times from several times to 10 times.

  When the predetermined switching time is over, switching to the adjacent antenna (in this case, antenna 32 (ANT2)) is performed, and the product is accessed in the next step (S5). In the area of step 2 as well, the same processing as in the area of step 1 is performed (S1 to S5 above).

  When the process is completed up to the antenna 34 (ANT4), the antenna 1 is switched to the antenna 1 again, and the antennas 31 to 34 are switched cyclically (S6).

  Here, a change in the reception level of the tag information by the reader / writer when the product moves in the process area will be described. FIG. 5 shows the time change of the RSSI value when the tagged product is conveyed in one process. In the figure, the relationship between the product position and the reception levels (P1 to P5) at five times (t1 to t5) is shown. Pth indicates a threshold level. When the product crosses the beam width of the main beam of the reader / writer, the antenna gain is low and the reception level is low (t1, P1) because it is received at the end of the main beam of the antenna and the side lobe outside the process area. However, since the reception level is higher than the reception sensitivity, tag information reception detection can be performed. Thereafter, the process enters the process area and the reception level increases (t2, P2). As the antenna approaches the middle of the process area (near the center of the main beam), the antenna gain gradually increases, so that the reception level increases and becomes the maximum reception level (t3, P3). Thereafter, when proceeding toward the process area exit, the antenna gain decreases and the reception level also decreases (t4, P4), and the process proceeds to the adjacent subsequent process (t5, P5).

  In the description of the above flow, “determination of reception level (S43) → send product information to PC (S44)” is performed every time the tag is accessed, but the present invention is not limited to this method. For example, the received data received by accessing the tag from each antenna during the switching period of one cycle of the antennas 31 to 34 (ANT1 to 4) are temporarily stored in the reader / writer device, and then collectively received. “Level determination → Send product information to PC” may be performed. The flow of another embodiment described later (FIG. 9) describes a case where processing is performed in this manner.

  The present invention monitors the reception level and detects the presence of a product in the process area when the reception level exceeds a predetermined reference value. As described above, even when a product is present in an adjacent area, the tag information is read, resulting in a reading error (detected by the antenna in the area although it is in the adjacent area). Therefore, it is necessary to set a constant cut-off level. As a method of setting this reference value, it can be determined that a product exists when a product exists in the area, and if a product exists in an adjacent area, it is determined that there is no product in the area. The level that can be done will be set. Accordingly, the threshold (reference level) is set to a predetermined value that is equal to or less than the peak value of the main lobe and exceeds the level at which the side lobe level and the data of the adjacent area at the base of the main lobe are not read. In FIG. 5, the thick line portion of the reception level characteristic curve is a portion exceeding the threshold, and is included in the process area. In the above case, the level at the times t2, t3, and t4 exceeds the reference value. This reference value is set in the memory in the determination unit 473 by the process management parameter unit 501. When the width of the process area is narrowed, this reference value increases the overlap between adjacent main lobes, so that it is necessary to set the reference value to be considerably high. However, if it is too high, the detection level that can be detected is limited. If a level fluctuation occurs, it may cause a malfunction such as omission of detection, and it cannot be made too high.

  The determination result as to whether the tag ID recognized by the tag recognition unit 442 and the tag ID determined by the determination unit 443 belong to a product existing in the area is sent to the history management unit 502 and recorded in association therewith. Is done.

  FIG. 6 shows the time change of the RSSI value when the tagged product is conveyed in the entire process (processes 1 to 4). (A) shows the time change of the reception level of the tag information reception signal by the reader / writer device, and (b) shows the determination result in the reception signal determination unit (determination result as a reception signal corresponding to each antenna device). It shows the time change. When the reference value (Pth) is set as described with reference to FIG. 5, it can be determined that a product is present in the process only when the RSSI level exceeds the reference value (FIG. 6B).

  FIG. 7 shows an example of history management in the history management unit 502. History management is performed for each tag ID. In the figure, the history of steps 1 to 4 is managed for each tag identification number corresponding to a product. A start time, an end time, and a status are recorded for each process. For TAG1, all the steps from Step 1 to Step 4 have been completed. For TAG2, it is recorded that process 2 has been completed, and process 3 has been started. For TAG3, it is recorded that the process has started for process 1.

  In the above description, the same reference value is used in steps 1 to 4 in the above description. However, the characteristics of the antenna device may vary individually, and the actual reception characteristics may differ depending on the antenna arrangement. In such a case, the determination reference value may be set independently for each antenna device arranged in each process.

  In the above-described embodiment, the case where the presence in the process area of the product is determined only by the reference value is shown. However, in an actual process line, reception characteristics fluctuate (fading) due to the influence of installation equipment such as manufacturing machinery around the line. As a result, a local peak occurs at the end of the main lobe and may exceed the reference value. FIG. 8 illustrates an example of a malfunction in such a case. A local peak of the antenna 31 (ANT1) is generated in the area of step 2 and exceeds the reference value. In this case, in the determination process based only on the reference value in the first embodiment, the antenna 31 detects the article even though the article exists in the area of step 2, and the same article is found in the process area 1 as well. It is judged as if it exists (FIG. 8B).

  In another embodiment described below, in order to cope with such a case, the tag information is determined to have a hysteresis characteristic. Specifically, once it is determined that the reception process with the antenna in the previous process has been completed, the reception process with the antenna in the previous process is temporarily stopped when the reception process with the antenna in the process is started. Even if it is performed, the reception process by the antenna in the previous process is not detected.

  FIG. 9 shows a schematic flowchart of data determination processing having hysteresis characteristics. The tag information of the product flowing through the process line is read for a predetermined time by the antennas 31 to 34 (ANT1 to ANT4) (S100). The reception level of the read data is determined based on the reference value described in the first embodiment, and the reception data existence time for each antenna is measured (S101). The presence times of received data at adjacent antennas (corresponding to adjacent steps) are compared to determine whether the data existence times overlap (S102). If the data existence times overlap, the received data of the overlapping time part by the previous process of the adjacent process is regarded as an error (S103). Data excluding the data portion determined to be an error is sent as product information to the signal processing unit (S104).

  Since the hysteresis characteristic is provided in the processing of the reception data in this way, the process management can be performed more accurately even when the reception characteristic of the reader / writer device is fluctuated due to fading or the like.

It is a block diagram of the process management system using RFID which concerns on Embodiment 1 of this invention. 1 is a configuration diagram of an RFID system according to the present invention. 3 is a flowchart of the RFID system according to the present invention. It is explanatory drawing of the directional characteristic of the antenna apparatus which concerns on this invention. It is a level change figure in one process area of the RFID system which concerns on this invention. It is a level change figure of the whole process of the RFID system concerning this invention. 3 is a product history management table of the RFID system according to the present invention. It is a level change figure of the whole process of the RFID system concerning other examples of this invention. It is a flowchart of the hysteresis characteristic of the RFID system which concerns on the other Example of this invention.

Explanation of symbols

11-14 process area, 21 products, 22 tags, 31-34 antenna,
40 reader / writer, 41 RF unit, 42 time division control switch, 43 transmitting unit,
44 receiver, 45 local transmitter, 46 circulator,
47 baseband section, 50 signal processor, 431 modulation section,
432 power amplifier, 441 low noise amplifier, 442 demodulator,
443 level detector, 471 tag command generation unit, 472 tag ID recognition unit,
473 determination unit, 474 switch control unit, 501 process parameter setting unit,
502 History management unit.

Claims (2)

A process management system for managing the history of each production process performed sequentially on an article,
A tag affixed to the article and identified in association with the article;
An antenna that is provided for each production process, transmits a read signal to the tag, and receives a response signal including identification information from the tag in response to the read signal;
A transmitter for generating the read signal;
A receiving unit for detecting a reception level from the response signal;
A switching unit for switching the connection between the antenna and the transmitting unit and the receiving unit;
A determination unit that determines the presence or absence of an article in the process by comparing the reception level with a predetermined reference value;
A process management system comprising: a management unit that manages production process history by associating each production process with an article existing in the process based on the determination result. The switching unit sequentially switches the antenna provided in each production process along the flow of the process, the receiving unit sequentially detects the reception level of the response signal received by each antenna, and the determination unit is adjacent Among the two processes, if the reception level by the antenna provided in the previous process exceeds the reference value and the reception level by the antenna provided in the subsequent process exceeds the reference value, there is an article in the subsequent process. The process management system according to claim 1, wherein determination is made.

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