Patent Publication Number: US-2009224040-A1

Title: Item management system and information processing device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2008-057197, filed Mar. 7, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an item management system and an information processing device for managing items such as retail products and parts. 
     2. Description of the Related Art 
     In a store or warehouse, management tasks for items such as retail products and parts are usually conducted by a store clerk or a warehouse worker by visual checking. Such tasks, however, are time-consuming and thus difficult to perform in an efficient manner. Furthermore, errors can be easily made. For these reasons, a system that reduces human work has been sought. Recently, wireless IC tags such as Radio Frequency Identification (RFID) tags have been developed. Jpn. Pat. Appln. KOKAI Publication No. 2001-031218 suggests a merchandise management system, in which an RFID tag with an identification code of a retail product written therein is attached to the product to manage products in a store or warehouse. 
     According to this document, a reading unit that exchanges signals with RFID tags is provided in each display section. Each section is given an individual address so that merchandise management can be conducted in accordance with identification codes transmitted from the reading unit and addresses of the sections. 
     On retail premises such as a convenience store, various kinds of products having relatively small outer dimensions are often displayed in limited spaces. Products of each kind are placed in a tight section of space, and products of similar kinds are packed next to one another. As an important factor of sales strategy in a store, items that are receiving attention need to be displayed at a position that customers can easily find. For this reason, regardless of the tightness of the display space, it is important to accurately identify the display positions of products and manage them so that the products are always displayed at predetermined positions. In a warehouse also, it is necessary, when carrying products or parts in and out, to identify where the items are stored and manage them so that they are always stored at predetermined positions. 
     The system disclosed in the above patent document identifies the position of a product in accordance with the address of the section where the reading unit is placed. If each display section is defined to have a large area, the distance between the reading units individually positioned in the sections is increased, which makes the locating of the display position unclear. If each display section is defined to have a small area, the distance between the reading units of the sections is shortened. Then, it is difficult to accurately locate the display position because the reading units may cause interference with one another, or may mistakenly read a RFID tag of an adjacent section. 
     BRIEF SUMMARY OF THE INVENTION 
     The purpose of the present invention is to offer an item management system and an information processing device for managing the locations of items in a store or a warehouse. 
     The item management system according to an embodiment of the present invention comprises an item placement position memory unit that stores item identification information of an item placed on a placement unit and item position information which indicates a position at which the item is placed; a wireless tag reading unit that reads a wireless tag attached to the item and outputs wireless tag readout information; an item identification information acquiring unit that acquires the item identification information of the item based on the wireless tag readout information output by the wireless tag reading unit; an object detecting unit that detects an object approaching the placement unit that carries the item thereon and outputs object position information; an item position identifying unit that associates the item identification information and the object position information with each other and outputs associated information as item position identification information; and an item position determining unit that compares the item position identification information output by the item position identifying unit with the item position information stored in the item placement position memory unit and outputs a comparison result. 
     Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a diagram of a system structure according to the first embodiment of the present invention. 
         FIG. 2  is a diagram of a hardware structure of a sensor according to the embodiment. 
         FIG. 3  is a diagram of a hardware structure of a RFID tag reader according to the embodiment. 
         FIG. 4  is a diagram of a hardware structure of a system management unit according to the embodiment. 
         FIG. 5  is a diagram of a structure of the sensor according to the embodiment. 
         FIG. 6  is a diagram of a structure of a sensor unit and a product display shelf unit according to the embodiment. 
         FIG. 7  is a diagram of a structure of a sensor unit and a product display shelf unit according to the embodiment. 
         FIG. 8  is a diagram showing the data structure of an object position data table according to the embodiment. 
         FIG. 9  is a diagram showing the data structure of an effective area table according to the embodiment. 
         FIG. 10  is a diagram showing the data structure of a planogram table according to the embodiment. 
         FIG. 11  is a diagram showing the data structure of a RFID tag memory table according to the embodiment. 
         FIG. 12  is a diagram showing the data structure of a RFID tag data buffer according to the embodiment. 
         FIG. 13  is a diagram showing the data structure of a RFID tag data table according to the embodiment. 
         FIG. 14  is a diagram showing the data structure of an item position identification table according to the embodiment. 
         FIG. 15  is a diagram showing a display screen of an output unit of a system management unit according to the embodiment. 
         FIG. 16  is a diagram showing another display screen of the output unit of the system management unit according to the embodiment. 
         FIG. 17  is a flowchart showing the procedure of a main process of the item management system according to the embodiment. 
         FIG. 18  is a flowchart showing the procedure of an object detecting process according to the embodiment. 
         FIG. 19  is a flowchart showing the procedure of a RFID tag reading process according to the embodiment. 
         FIG. 20  is a flowchart showing the procedure of an item position identifying process according to the embodiment. 
         FIG. 21  is a flowchart showing the procedure of a main process of an item management system according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiment 1 
     Exemplary embodiments of the present invention will be explained with reference to the attached drawings. 
       FIG. 1  is a diagram of a structure of an item management system  90  according to the first embodiment of the present invention. The item management system  90  comprises a sensor unit  20  (object detecting unit), a RFID tag reader unit  40  (wireless tag reading unit), and a system management unit  60  (information processing device). 
     A sensor unit  20  is composed of sensors  20   a,    20   b  and  20   c  that are arranged in correspondence with individual shelves of a product display shelf unit  1  (placement unit) in a retail store. The sensor unit  20  detects a product  2  (item) placed on the product display shelf unit  1  or an object  3  approaching a product display area  8  (item placement area), and measures the distance between the corresponding sensor and the object  3 . The sensor unit  20  transmits the measured distance to the system management unit  60  as object position data (object position information) of the object  3 . Because the sensors  20   a,    20   b  and  20   c  have the same hardware structure and the same function, the sensor  20   b  will be mainly discussed as an object detecting unit in the present embodiment. 
     The sensor  20   b  can measure the distance from the object  3  by a method of adopting an infrared laser beam. According to this method, projection light  30 , which is an infrared laser beam having a wavelength of 0.7 μm to 0.1 mm, is projected from the sensor  20   b  onto the object  3 , and reflection light  31  reflected from the object  3  is detected by the sensor  20   b.  Based on a time difference between the time at which the projection light  30  is projected and the time at which the reflection light  31  is detected, the distance from the object  3  is calculated. The to-be-detected object  3  may be the hand or arm of a store clerk or a person who is carrying merchandise in and out, or may be the merchandise itself. The object  3  also could be an arm of a merchandise carrying robot or the like. 
     The RFID tag reader unit  40  is composed of a RFID tag reader  41  and an antenna  42 . The RFID tag reader  41  modulates a read signal to read a RFID tag  43 . The antenna  42  sequentially transmits read waves  44  that are obtained as a result of the modulation by the RFID tag reader  41 . The antenna  42  also receives response waves  45  from the RFID tag  43 . When the antenna  42  receives response waves  45  from a RFID tag  43  located in the communication area, the RFID tag reader  41  demodulates the radio waves and stores response data in the RFID tag reader  41 . The response data is RFID tag readout data (wireless tag readout information) recorded in the RFID tag  43 , including a tag code, which is a tag identification code, and product data such as a product code for identifying a product and the name of the product. 
     The system management unit  60  is connected to the sensor unit  20  and the RFID tag reader unit  40  on a communications line  80  such as a LAN or a dedicated line. The system management unit  60  performs a process based on the object position data of the object  3  output by the sensors and the RFID tag readout data acquired from the RFID tag reader unit  40 . 
       FIG. 2  is a diagram showing a hardware structure of the sensor  20   b  of the item management system  90 . The sensor  20   b  comprises a micro processing unit (MPU)  21 , a light emitting unit  22  (light projecting unit), a light receiving unit  23  (detecting unit), a timer unit  26 , a memory unit  27 , a communication unit  28 , a power supply unit  29 , and the like. The MPU  21  is a controller that controls the hardware units of the sensor  20   b . The light emitting unit  22  emits the projection light  30  to detect the object  3 . The light receiving unit  23  detects reflection light  31  from the object  3 . The memory unit  27  is a hard disk or a memory. The communication unit  28  exchanges data with the system management unit  60 . 
       FIG. 3  is a diagram showing the hardware structure of the RFID tag reader unit  40  of the item management system  90 . The RFID tag reader unit  40  includes the RFID tag reader  41  and the antenna  42 . The RFID tag reader  41  includes a micro processing unit (MPU)  46 , a timer unit  47 , a memory unit  48 , a communication unit  49 , a power supply unit  50 , a wireless communication unit  51 , and the like. The MPU  46  is a controller that controls the hardware units. The memory unit  48  is a memory or the like. The communication unit  49  exchanges data with the system management unit  60 . The wireless communication unit  51  conducts communications with the RFID tag  43  by way of the antenna  42 . The memory unit  48  of the RFID tag reader  41  includes a RFID tag data buffer  160  to store a tag code, a product code and the name of the product received from the RFID tag  43 . The RFID tag  43  is composed of an antenna  52 , a wireless communication unit  53 , and a memory unit  54 . The memory unit  54  includes a RFID tag memory table  115 . 
       FIG. 4  is a diagram for showing the hardware structure of the system management unit  60  of the item management system  90 . The system management unit  60  includes a micro processing unit (MPU)  61 , an input unit  62 , an output unit  63 , a memory unit  64 , a timer unit  65 , a communication unit  66 , a power supply unit  67 , and the like. The MPU  61  is a controller that controls the hardware units. The input unit  62  is an input device such as a keyboard and a mouse. The output unit  63  is an output device including a display such as a liquid crystal display or an organic EL display, and a printer. The memory unit  64  is a hard disk or a memory. The communication unit  66  exchanges data with the sensor unit  20 , the RFID tag reader unit  40  or any other system. The memory unit  64  holds a location data table  100 , an effective area table  110 , a RFID tag data table  120 , an item position identification table  130 , and a planogram table  170 . 
     Next, the sensor  20   b,  which serves as the object detecting unit of the item management system  90 , will be explained.  FIG. 5  is a diagram showing the structure of the sensor  20   b.  The sensor  20   b  comprises the light emitting unit  22  (light projecting unit), the light receiving unit  23  (detecting unit), a housing  32 , a sensor controlling unit  36 , and the like. The housing  32  is shaped into a cylinder and has a transparent window  34  formed to open 180 degrees in the circumferential direction. The light emitting unit  22  is a light source of an infrared laser or LED. The light receiving unit  23  may be a light sensor such as a photodiode. 
     The sensor controlling unit  36  functions as an object position calculating unit. The sensor controlling unit  36  comprises the MPU  21 , the timer unit  26 , the memory unit  27 , the communication unit  28 , the power supply unit  29  and the like. The sensor controlling unit  36  controls the emission of the light emitting unit  22 , and measures and calculates the distance between the sensor  20   b  and the object  3 . 
     The distance calculation by use of the projection light  30  and the reflection light  31  may be a method using a time difference between the time of emission of the projection light  30  and the time of detection of the reflection light  31 , or by a method using a phase difference between the projection light  30  and the reflection light  31 . According to the time difference method, the light emitting unit  22  emits an infrared laser beam as projection light  30  in the form of short pulses, and the light receiving unit  23  detects the reflection light  31  of this beam. The MPU  21  calculates the distance based on a difference between the time of emission of the projection light  30  and the time of detection of the reflection light  31 , the length of time that it has taken for the light to travel from the projection light  30  and back, and the reference speed of the projection light  30  and the reflection light  31 . According to the phase difference method, the infrared laser beam incident from the light emitting unit  22  is modulated with a sinusoidal wave that maintains a certain frequency, and the distance is calculated based on the difference between the phases of the projection light  30  and the reflection light  31 . With the phase difference method, the distance cannot be calculated if the phase difference is larger than one cycle. Thus, the frequency for the modulation should be determined within a predetermined detection area. According to the present embodiment, the sensor  20   b  measures the distance from the object  3  by use of the projection light  30 , which is an infrared laser beam. In the same manner as the infrared laser beam, an ultrasonic wave, which is a sonic wave having a frequency of 20 kHz or higher, may be projected, and the reflection wave may be detected. Then, the distance from the object  3  can be calculated based on the time of projection of the ultrasonic wave and the time of detection of the reflection wave. 
     The sensor controlling unit  36  calculates the distance from the sensor  20   b  to the object  3  based on the difference between the time at which the light emitting unit  22  emits the projection light  30  and the time at which the light receiving unit  23  detects the reflection light  31  in accordance with the above method. The sensor controlling unit  36  transmits to the system management unit  60  the object position data, which includes the calculated distance data, the sensor identification data that identifies the sensor  20   b,  and the sensor detection time data that represents the time of detection of the reflection light  31 . Upon receipt of the object position data from the sensor  20   b,  the system management unit  60  executes the process based on the data. 
       FIG. 6  is a diagram of the product display shelf unit  1  (placement unit) provided with the sensor unit  20  which includes the sensors  20   a,    20   b  and  20   c.  The sensors detect the product  2  (item) displayed in the product display shelf unit  1  or the object  3  approaching the product display area  8  (item placement area) of the product  2 . The sensor unit  20  may be situated on the peripheral portion  5  of the front side  4  of the product display shelf unit  1 , where a product loading area  6  (opening) is provided. The projection light  30  horizontally projected from the sensors  20   a,    20   b  and  20   c  has a certain width, and therefore detection areas  7   a,    7   b  and  7   c  are created in the form of bands across the front of the product loading area  6  to serve as reference areas in detection of the object  3 . 
       FIG. 7  is a diagram of the product display shelf unit  1  that is sectioned into blocks  10 , A 1  to A 12 , in order to display different kinds of products  2 . The areas of the blocks Al to A 12  are determined in accordance with the sizes of the sections in which the products  2  are displayed. According to the present embodiment, all the blocks A 1  to A 12  have the same size, 50 cm long and 80 cm wide, but the size is not limited thereto. The blocks A 1  to A 12  may be determined to have different sizes. According to the present embodiment, the product display shelf unit  1  is 320 cm wide in the X-axis direction, when referring to a reference line  11  connecting the positions of the sensors  20   a,    20   b  and  20   c.  The detection areas  7   a,    7   b  and  7   c  defined by the projection light  30  incident from the sensors  20   a,    20   b  and  20   c  are laid across the product loading area  6  of the product display shelf unit  1  in the form of bands. For this reason, the sensors  20   a,    20   b  and  20   c  detect not only the product  2  displayed in the product display shelf unit  1  or the object  3  approaching the product display area  8 , but also fixed background objects  9 , including pillars and walls of the retail premises on which the product display shelf unit  1  is situated, a store clerk or a customer standing next to the product display shelf unit  1 , and moving objects such as a cart and other equipment. The item management system  90  is supposed to identify the position of the product  2  displayed in the product display shelf unit  1 , and thus the positional data of the background objects should be excluded from detection targets. The system management unit  60  according to the present invention determines the rear end of the product display shelf unit  1  in the X-axis direction as the upper limit of the effective detection area in order to exclude the positional data of those background objects. The system management unit  60  performs a process of excluding the positional data of any object detected beyond effective detection areas  12   a,    12   b  and  12   c,  which are part of the detection areas  7   a,    7   b  and  7   c  between the sensors  20   a,    20   b  and  20   c  and the upper limit. 
       FIG. 8  is a diagram showing the structure of an object position data table  100  stored in the memory unit  64  of the system management unit  60 . The object position data table  100  includes a sensor identification data field  101 , a distance field  102 , a sensor detection time field  103 , and a detection object field  104 . The sensor identification data field  101  maintains the sensor identification data that is output by the sensors  20   a,    20   b  and  20   c  to identify the sensors. The distance field  102  maintains the distance data. The sensor detection time field  103  maintains the detection time data representing the time at which the object is detected. The sensor identification data, the distance data and the detection time data constitute the object position data. The detection object field  104  holds “1” when the positional data is judged as data of a detection target in the effective information extracting process, while the detection object field  104  holds “0” when the positional data is not judged as data of a detection target. Whether the object can be a detection target is determined based on the data in the detection object field  104 . 
       FIG. 9  is a diagram showing the structure of the effective area table  110  stored in the memory unit  64  of the system management unit  60 . The effective area table  110  functions as an effective area memory unit. The effective area table  110  maintains the upper limits of the sizes of the effective detection areas  12   a,    12   b  and  12   c  that are included in the detection areas  7   a,    7   b  and  7   c  defined by the sensors  20   a,    20   b  and  20   c.  The effective area table  110  includes a sensor identification data field  111  that holds identification data of each sensor, a shelf field  112  that holds shelf data to identify the shelf on which the sensor is provided, and an upper limit field  113  that holds the upper limit of the effective detection area (area information) for each sensor. According to the present embodiment, the upper limit field  113  holds the upper limit of 320 cm, which is the dimension of the product display shelf unit  1 . The positional data beyond this limit is eliminated from the data of the detection targets in the effective information extracting process because it can be considered as background position data of a background object  9  or the like that is positioned outside the effective detection areas  12   a,    12   b,  and  12   c  but is detected by the projection light  30  reflected thereon. 
       FIG. 10  is a diagram showing the structure of the planogram table  170  stored in the memory unit  64  of the system management unit  60 . The planogram table  170  serves as an item placement position memory unit. The planogram table  170  includes, in association with a block field  171 , a shelf field  172  that holds the shelves on which the blocks Al to A 12  of the product display shelf unit  1  are positioned, a range field  173  that holds the positional ranges of the blocks, and a product code field  174  that holds the product codes (item identification information) of the products  2  (items) displayed in the blocks. The range data stored in the range field  173  represents the range of a block in the X-axis direction, when referring to the reference line  11  that connects the sensors  20   a,    20   b  and  20   c  of the product display shelf unit  1  to one another. The block data in the block field  171  serves as item position information. 
       FIG. 11  is a diagram showing the structure of the RFID tag memory table  115  stored in the memory unit  54  of the RFID tag  43 . The RFID tag memory table  115  includes a tag code field  116  that holds tag codes for identifying RFID tags, a product code field  117  that holds product codes for identifying the products, and a product name field  118  that holds the names of the products. 
       FIG. 12  is a diagram showing the structure of the RFID tag data buffer  160  stored in the memory unit  48  of the RFID tag reader  41 . The RFID tag data buffer  160  includes a tag code field  161 , a product code field  162 , and a product name field  163 . 
       FIG. 13  is a diagram showing the structure of the RFID tag data table  120  stored in the memory unit  64  of the system management unit  60 . The RFID tag data table  120  includes a RFID tag readout data field  121 , a read time field  122 , a difference data field  123  and an update state field  124 . 
       FIG. 14  is a diagram showing the structure of the item position identification table  130  stored in the memory unit  64  of the system management unit  60 . The item position identification table  130  includes a shelf field  131  that holds the object position data, a distance field  132 , a block field  133 , a sensor detection time field  134 , a tag code field  135 , a product code field  136 , a product name field  137 , and an update state field  138 . 
       FIG. 15  is a diagram of a display screen  140 . The display screen  140  is output on the output unit  63  of the system management unit  60  such as a liquid crystal display or an organic EL display. 
       FIG. 16  is a diagram of a display screen  190 . The display screen  190  serves as item position warning information. The display screen  190  is output onto the output unit  63  of the system management unit  60  such as a liquid crystal display and an organic EL display. The display screen  190  includes display entries  191  of item position identification information in which an error is made, an error message  192 , and the like. 
     Next, the process performed by the item management system  90  is explained with reference to the flowcharts of  FIGS. 17 to 20 .  FIG. 17  is a flowchart of the main process executed by the MPU  61 , which is the controller of the system management unit  60 . The MPU  61  of the system management unit  60  awaits an interrupt from the object detecting process that is performed when the sensor unit  20  detects the object  3  (Step S 1 ). 
     The object detecting process is now explained.  FIG. 18  is a flowchart of the object detecting process executed by the MPU  61 , which is the controller of the system management unit  60 . The object detecting process serves as an object position information acquiring unit. The sensor unit  20 , composed of the sensors  20   a,    20   b  and  20   c,  calculates the distance data of the object  3 . Then, the sensor unit  20  transmits to the system management unit  60  the object position data (object position information), which includes the sensor identification data that identifies a sensor, the distance data, the detection time data that represents the time of detection of the object  3 , and the like. The system management unit  60  is on standby until the object position data detected by the sensor unit  20  is received from the sensor unit  20  (Step S 31 ). 
     When the object position data is received from any of the sensors  20   a,    20   b  and  20   c  (YES at Step S 31 ), the MPU  61  stores the object position data in the object position data table  100  (Step S 33 ). At this step, the MPU  61  stores the sensor identification data of the object position data in the sensor identification data field  101 , the distance data in the distance field  102 , and the detection time data in the sensor detection time field  103 . 
     Next, the MPU  61  compares the distance data stored in the distance field  102  of the object position data table  100  with the upper limit data of the effective detection areas  12  (effective detection areas  12   a,    12   b  and  12   c ) stored in the upper limit field  113  of the effective area table  110  (Step S 35 ). 
     Then, the MPU  61  determines whether the distance data stored in the distance field  102  of the object position data table  100  falls within the upper limit data stored in the upper limit field  113  of the effective area table  110  (Step S 37 ). When the distance data is beyond the upper limit data (NO at Step S 37 ), it means that the object  3  is detected outside the effective detection area  12  of the product display shelf unit  1 . In this case, the MPU  61  stores “0” in the detection object field  104  of the object position data table  100  (Step S 43 ), and terminates the object detecting process. 
     When the distance data falls within the upper limit data (YES at Step S 37 ), it means that the object  3  is detected in the effective detection area  12  of the product display shelf unit  1 . In this case, the MPU  61  stores “1” in the detection object field  104  of the object position data table  100  (Step S 39 ). Then, the MPU  61  issues an interrupt to the main process (Step S 41 ). Thereafter, the MPU  61  terminates the object detecting process. 
     In the object detecting process, the MPU  61  stores the object position data (the sensor identification data, distance data, and detection time data) in the object position data table  100 . Furthermore, the MPU  61  determines whether the position of the detected object  3  falls within the effective detection area  12  (any of the effective detection areas  12   a,    12   b  and  12   c ) of the sensor unit  20  (sensors  20   a,    20   b  and  20   c  ), and stores the result in the object position data table  100 . This is because detection targets should be limited to products  2  displayed in the product display shelf unit  1  and objects  3  approaching the product display area  8 . In this manner, the positional data of store clerks and customers moving near the product display shelf unit  1 , or pillars, walls and any equipment surrounding the product display shelf unit  1  is eliminated from the data of the detection targets, because these are background objects that are unrelated to the detection of objects approaching the product  2 . 
     In the flowchart of  FIG. 17 , when an interrupt is issued from the object detecting process (YES at Step S 1 ), the MPU  61  executes a RFID tag reading process (Step S 3 ). 
       FIG. 19  is a flowchart of the RFID tag reading process executed by the MPU  61 , which is the controller of the system management unit  60 . The RFID tag reading process serves as an item identification information acquiring unit and a wireless tag readout information acquiring unit. When the item management system  90  is started, the RFID tag reader unit  40  sequentially transmits read waves  44  through the antenna  42  to read a RFID tag  43 . Upon receipt of the response waves  45  from the RFID tag  43 , the RFID tag reader unit  40  reads data stored in the memory unit  54  of this RFID tag  43 , including a tag code, product code and name of the product from the radio waves. The RFID tag reader unit  40  stores the RFID tag readout data composed of these data items in the RFID tag data buffer  160  provided in the memory unit  48  of the RFID tag reader  41 . The RFID tag reader unit  40  conducts a search through the RFID tag data buffer  160  by use of the read-out tag code. When the same tag code is stored in the RFID tag data buffer  160 , the RFID tag reader unit  40  abandons the RFID tag readout data that is read out. On the other hand, when no tag code the same as the read-out tag code is stored, the RFID tag reader unit  40  does not abandon the RFID tag readout data that is read out. Because no tag codes that are the same are stored, overlapping data reading can be avoided. 
     The MPU  61  starts up the timer  65  (Step S 51 ). Then, the MPU  61  requests that the RFID tag reader unit  40  transmit the RFID tag readout data read by the RFID tag reader unit  40  (Step S 53 ). On request of the transmission of the RFID tag readout data from the system management unit  60 , the RFID tag reader unit  40  transmits the RFID tag readout data stored in the RFID tag data buffer  160  that is provided in the memory unit  48  of the RFID tag reader  41 , to the system management unit  60 . 
     When receiving the RFID tag readout data from the RFID tag reader unit  40  (Step S 55 ), the MPU  61  compares the received RFID tag readout data and the previous RFID tag readout data stored in the RFID tag data table  120  (Step S 57 ). Then, the MPU  61  determines whether there is any difference between the RFID tag readout data received at Step S 55  and the previous RFID tag readout data (Step S 59 ). According to the present embodiment, the RFID tag readout data including the tag code, product code, and name of the product is used for the comparison and determination. However, because no pair of identical tag codes are stored, only the tag code may be used for the comparison and determination. 
     When the MPU  61  determines that there is no difference between the RFID tag readout data received at Step S 55  and the previous RFID tag readout data (NO at Step S 59 ), the MPU  61  then determines whether the timer indicates that a predetermined time period has elapsed (Step S 73 ). When the MPU  61  determines that a predetermined time period has not yet elapsed (NO at Step S 73 ), the process returns to Step S 53 , and repeats the operation of Steps S 53  to S 59 . When the MPU  61  determines that a predetermined time period has elapsed (YES at Step S 73 ), the MPU  61  stops and resets the timer (Step S 75 ). Then, the MPU  61  stores the RFID tag readout data received at Step S 55  in the RFID tag data table  120  (Step S 77 ). In this operation, the MPU  61  stores the tag code, product code, and name of the product of the RFID tag readout data received at Step S 55  in the RFID tag readout data field  121  of the RFID tag data table  120 , and also stores the read time data, which indicates the time at which the RFID tag readout data is received from the RFID tag reader unit  40 , in the read time field  122 . The MPU  61  does not store any data in the difference data field  123  or the update state field  124 . Then, the MPU  61  terminates the RFID tag reading process. 
     When the MPU  61  determines at Step S 59  that there is a difference between the RFID tag readout data received at Step S 55  and the previous RFID tag readout data (YES at Step S 59 ), the MPU  61  stops and resets the timer (Step S 61 ). Then, the MPU  61  stores the RFID tag readout data received at Step S 55  in the RFID tag data table  120  (Step S 63 ). In this operation, the MPU  61  stores the tag code, product code, and name of the product of the RFID tag readout data received at Step S 55  in the RFID tag readout data field  121  of the RFID tag data table  120 , and the read time data which indicates the time at which the RFID tag readout data is received from the RFID tag reader unit  40  in the read time field  122 . Then, the MPU  61  stores the RFID tag readout data that is different from the previous RFID tag readout data in the difference data field  123  (Step S 65 ). 
     Next, the MPU  61  determines whether the RFID tag readout data stored in the difference data field  123  is data that is added to the previous RFID tag readout data or deleted therefrom (Step S 67 ). In comparison of the latest RFID tag readout data with the previous RFID tag readout data, if the RFID tag readout data stored in the difference data field  123  exists in the latest RFID tag readout data but not in the previous RFID tag readout data, it is added data. On the other hand, if the RFID tag readout data stored in the difference data field  123  exists in the previous RFID tag readout data but not in the latest RFID tag readout data, it is deleted data. When the MPU  61  determines that the RFID tag readout data stored in the difference data field  123  is not added data (NO at Step S 67 ), the MPU  61  enters “0” in the update state field  124  of the RFID tag data table  120  (Step S 71 ). Then, the MPU  61  terminates the RFID tag reading process. The value “0” entered in the update state field  124  means that the RFID tag  43  having this tag code has been removed from the product display shelf unit  1 , which is in the communication area of the RFID tag reader unit  40 . When the MPU  61  determines that the RFID tag readout data stored in the difference data field  123  is added data (YES at Step S 67 ), the MPU  61  enters “1” in the update state field  124  of the RFID tag data table  120  (Step S 71 ). Then, the MPU  61  terminates the RFID tag reading process. The value “1” entered in the update state field  124  means that the RFID tag  43  having this tag code has been added to the product display shelf unit  1  that is in the communication area of the RFID tag reader unit  40 . 
     In the RFID tag reading process, the MPU  61  acquires the product data such as a product code and the name of the product from the RFID read data, and stores it in the RFID tag data table  120 . Moreover, when a new RFID tag  43  is read out, the MPU  61  enters “1” in the update state field  124  of the RFID tag data table  120  to indicate that the data is “added”. On the other hand, when a RFID tag  43  is no longer readable, the MPU  61  enters “0” in the update state field  124  to indicate that the data is “deleted”. Based on the readout result of the RFID tag  43 , it can be determined whether a product  2  is loaded onto the product display shelf unit  1 , which is the communication area of the RFID tag reader unit  40 , or the product  2  is taken away from the product display shelf unit  1 . Furthermore, “1” or “0” entered in the update state field  124  of the RFID tag data table  120  means that some change has been made to the RFID tag readout data of the RFID tag  43 , which is the readout result. 
     In the flowchart of  FIG. 17 , the MPU  61  determines whether any change is made to the RFID tag readout data as a result of the RFID tag reading process (Step S 5 ). More specifically, the MPU  61  determines whether “1” or “0” is entered in the update state field  124  of the latest RFID tag readout data stored in the RFID tag data table  120 . When there is no change in the RFID tag readout data, or in other words when neither “1” nor “0” is entered in the update state field  124  (NO at Step S 5 ), it means that no change is made to the result of reading the RFID tag  43  out despite the detection of the object  3 . If this is the case, there is a possibility of a malfunction in the sensor unit  20 , the RFID tag reader unit  40  or the RFID tag  43 . Thus, the MPU  61  audibly or visually outputs warning information such as an error sound or a message to notify the store clerk (Step S 9 ). Thereafter, the MPU  61  returns to the operation of Step S 1 . 
     At Step S 5 , when there is some change to the RFID tag readout data, or in other words when “1” or “0” is entered in the update state field  124  for the latest RFID tag readout data stored in the RFID tag data table  120  (YES at Step S 5 ), the MPU  61  executes the item position identifying process (Step S 7 ). 
       FIG. 20  is a flowchart of the item position identifying process executed by the MPU  61 , which is the controller of the system management unit  60 . The item position identifying process serves as an item position identifying unit and an item position determining unit. First, the MPU  61  stores, in the item position identification table  130 , object position data for which “1” is entered in the detection object field  104  of the object position data table  100  (Step S 91 ). The MPU  61  acquires the shelf data corresponding to the sensor identification data from the shelf field  112  of the effective area table  110 , and stores the acquired shelf data in the shelf field  131 , the distance data in the distance field  132  and the detection time data in the sensor detection time field  134 . 
     The MPU  61  stores the same shelf data as the shelf data stored in the shelf field  131  of the item position identification table  130 , and searches through the planogram table  170  for a block that matches the range data in which the distance data stored in the distance field  132  of the item position identification table  130  is included. Then, the MPU  61  stores the block data that meets the search criteria in the block field  133  of the item position identification table  130  (Step S 93 ). The block data stored in the block field  133  serves as item position identification information. 
     Next, the MPU  61  compares the detection time data in the sensor detection time field  134  with the read time data for the latest RFID tag readout data in the read time field  122  of the RFID tag data table  120  (Step S 95 ). The MPU  61  determines whether the difference between the detection time data of the sensor detection time field  134  and the read time data of the read time field  122  is within a predetermined time period (Step S 97 ). If it is determined that the difference is not within the time period (NO at Step S 97 ), it means that there is no change in the result of reading the RFID tag  43  despite the detection of the object  3  within the predetermined time period. If this is the case, there is a possibility of a malfunction in the sensor unit  20 , the RFID tag reader unit  40  or the RFID tag  43 . Thus, the MPU  61  audibly or visually outputs warning information, such as an error sound and message to notify the store clerk (Step S 111 ). Thereafter, the MPU  61  terminates the item position identifying process. For instance, the predetermined time period for the determining process of Step S 97  may be set to three seconds so that warning information can be output when there is no change in the result of reading the RFID tag  43  in three seconds after detecting the object  3 . 
     When the MPU  61  determines that the difference between the detection time data in the sensor detection time field  134  and the read time data in the read time field  122  is within the predetermined time period (YES at Step S 97 ), the MPU  61  stores the RFID tag readout data in the item position identification table  130  in association with the object position data stored at Step S 91  (Step S 99 ). In this operation, the MPU  61  stores the tag code stored in the difference data field  123  of the RFID tag data table  120  in the tag code field  135  of the item position identification table  130 , the product code stored in the difference data field  123  in the product code field  136 , the product name data stored in the difference data field  123  in the product name field  137 , and the update state data stored in the update state field  124  in the update state field  138 . 
     Next, the MPU  61  compares the item position information stored in the planogram table  170  with the item position identification information stored in the item position identification table  130  (Step S 101 ). In this operation, the MPU  61  conducts a search to determine whether the same product code as the product code stored in the product code field  136  of the item position identification table  130  is stored in the planogram table  170 . Then, the MPU  61  compares the block data stored in association with the product code that matches the search criteria with the data block stored in the block field  133  of the item position identification table  130 . 
     The MPU  61  determines whether the block data (item position identification information) stored in the block field  133  of the item position identification table  130  is the same as the block data (item position information) stored in the block field  171  of the planogram table  170  (Step S 103 ). When the MPU  61  determines that the block data of the item position identification table  130  is not the same as the block data of the planogram table  170  (NO at Step S 103 ), the MPU  61  conducts a search through the planogram table  170  to find any block data (item position information) stored in association with the same product code as the product code stored in the product code field  136  of the item position identification table  130  (Step S 107 ). The MPU  61  outputs the item position warning information, based on the block data that matches the search criteria (Step S 109 ). 
     The display screen  190  illustrated in  FIG. 16  is an output example of the item position warning information. The display screen  190  is displayed on a display, which is one example of the output unit  63  of the system management unit  60 . The display screen  190  is displayed by using a different color or style for the item position identification information that includes an error, as in the display entry  191 , from the one for the correct item position identification information that includes no error. Furthermore, the display screen  190  can notify the store clerk of the display position of a product that is incorrect and the correct display position of this product, by displaying an error message  192  or the like to provide correct item position information that represents the correct display position of the product. The message notifying the error in the display position and the correct display position of the product may be output by voice. After the item position warning information is output, the MPU  61  terminates the item position identifying process. 
     When the MPU  61  determines that the block data (item position identification information) stored in the block field  133  of the item position identification table  130  is the same as the block data (item position information) stored in the block field  171  of the planogram table  170  (YES at Step S 103 ), the item position identification information stored in the item position identification table  130  is output (Step S 105 ). 
     The display screen  140  illustrated in  FIG. 15  is an example output of the item position identification information. The display screen  140  shows the block data (item position identification information), detection times, names of products, and update state data. When the update state field  138  of the item, position identification table  130  shows “1”, which indicates the data being added, the item position identification information is displayed on the display, which is the output unit  63  of the system management unit  60 . This item position identification information is composed of the positional information of the product  2  (item) added to the product display shelf unit  1  (placement unit), the addition time information, the product data that identifies the product  2  such as the name of the product, and display information for “added” that indicates the product being added. When the update state field  138  of the item position identification table  130  shows “0”, which indicates the data being deleted, the item position identification information is also displayed on the display, which is the output unit  63  of the system management unit  60 . This item position identification information is composed of the positional information of the product  2  (item) removed from the product display shelf unit  1  (placement unit), the removal time information, the product data that identifies the product  2  such as the name of the product, and display information for “deleted” that indicates the product being removed. By referring to the item position identification information, the store clerk can visually check to see whether products are displayed in the correct positions. After outputting the item position identification information, the MPU  61  terminates the item position identifying process, and awaits the next interrupt from the object detecting process (Step S 1 ). 
     In the above explanation of the present embodiment, the display screen  140  on the display unit is adopted as an output mode of the item position identification information, but the output mode of the item position identification information is not limited thereto. The item position identification information stored in the item position identification table  130  may be output to a different software program without any change so that the item locations can be controlled in this software program. Moreover, the item position identification information may be printed out by a printing unit such as a printer so that the item locations can be managed with a written report or the like. 
     According to the first embodiment of the present invention, the MPU  61  identifies the positional information of the product  2  placed in the product display shelf unit  1  in accordance with the object position data output by the object detecting unit of the sensor unit  20 , and identifies the identification information of the product  2  in accordance with the RFID tag readout data output by the wireless tag reading unit of the RFID tag reader unit  40 . Furthermore, the MPU  61  associates the identified object position data with the RFID tag readout data, and outputs the item position identification information of the product  2  placed in the product display shelf unit  1 . Then, the MPU  61  compares the item position identification information with the item position information stored in the item placement position memory unit, and outputs the comparison result. In this manner, the result of comparing the item position identification information with the item position information is output and displayed on the output unit  63  of the system management unit  60  so that the store clerk or any other worker is notified of the accuracy of the task. 
     Embodiment 2 
     The second embodiment of the present invention will be explained with reference to  FIG. 21 . Any overlapping portion with the first embodiment will be omitted from the explanation. According to the first embodiment, the RFID tag reader unit  40  starts operating as soon as the system management unit  60  is started. According to the second embodiment, the RFID tag reader unit  40  starts operating when an interrupt is issued from the object detecting process. 
       FIG. 21  is a flowchart of the main process executed by the MPU  61 , which is the controller of the system management unit  60 . The MPU  61  of the system management unit  60  is on standby until the object position data is received from the sensor unit  20  and an interrupt is issued from the object detecting process (Step S 121 ). The object detecting process is the same as the process of the first embodiment, and thus is omitted from the explanation. 
     When an interrupt is issued from the object detecting process (YES at Step S 121 ), the MPU  61  starts the RFID tag reader unit  40  up (Step S 123 ). When the RFID tag reader unit  40  is started, the MPU  61  executes the RFID tag reading process (Step S 125 ). The RFID tag reading process is the same as the process of the first embodiment, and thus is omitted from the explanation. 
     When the RFID tag reading process is completed, the MPU  61  stops the RFID tag reader unit  40  (Step S 127 ). Next, the MPU  61  determines whether any change is made to the RFID tag readout data as a result of the RFID tag reading process (Step S 129 ). In other words, the MPU  61  determines whether “1” or “0” is entered in the update state field  124  for the latest RFID tag readout data stored in the RFID tag data table  120 . When there is no change in the RFID tag readout data, or in other words when neither “1” nor “0” is entered in the update state field  124  (NO at Step S 129 ), it means that no change is made to the readout result of the RFID tag  43  despite the detection of the object  3 . If this is the case, there is a possibility of a malfunction in the sensor unit  20 , the RFID tag reader unit  40  or the RFID tag  43 . Thus, the MPU  61  notifies the store clerk by audibly or visually outputting warning information such as an error sound and a message (Step S 133 ). Then, the MPU  61  returns to Step S 121 . 
     When there is a change in the RFID tag readout data in the operation at Step S 129 , or in other words when “1” or “0” is entered in the update state field  124  of the RFID tag data table  120  for the latest RFID tag readout data (YES at Step S 5 ), the MPU  61  executes the item position identifying process (Step S 131 ). The item position identifying process is the same as the process according to the first embodiment, and thus the explanation is omitted. When the item position identifying process is completed, the MPU  61  is on standby until an interrupt is issued from the object detecting process again (Step S 121 ). 
     According to the second embodiment of the present invention, the MPU  61  identifies the positional information of the product  2  placed in the product display shelf unit  1  in accordance with the object position data output by the object detecting unit of the sensor unit  20 , and also identifies the identification information of the product  2  in accordance with the RFID tag readout data output by the wireless tag reading unit of the RFID tag reader unit  40 . Then, the MPU  61  associates the object position data with the RFID tag readout data, and thereby outputs the positional information and identification information of the product  2  placed in the product display shelf unit  1 . Radio interference and erroneous reading by the wireless tag reading unit can be avoided because the positional information of items is detected by the object detecting unit that is separated from the wireless tag reading unit. This improves the accuracy in identifying the positions of the items. 
     Furthermore, the MPU  61  starts up the RFID tag reader unit  40  when an interrupt occurs from the object detecting unit, and the MPU  61  stops the RFID tag reader unit  40  when the RFID tag reading process is completed. Thus, the wireless tag reading unit starts up and reads the RFID tag  43  only when the object detecting unit detects the object  3 . In this manner, the power consumption of the RFID tag reader unit  40  can be reduced, and a system with reduced running costs can be realized. 
     According to the above embodiments, the present invention is applied to an item management system for managing sales products or any other items in a retail store, but the invention is not limited thereto. The present invention may be applied to an item management system for managing parts and materials in a warehouse or the like. 
     In addition, according to the embodiments, the shelves for displaying products are vertically arranged, but the arrangement is not limited thereto. The present invention may be applied to a table or rack having a substantially horizontal top surface divided into sections to display sales products. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.