Abstract:
A sensor system includes: a radio transmitting device transmitting a predetermined radio signal regularly; a sensor detecting opening/closing or locking/unlocking of a partition mechanism installed in a door of a building or a site; and an information processing device. The information processing device includes: a radio receiving part receiving the predetermined radio signal and result of detection of the sensor; a decision part deciding whether or not a person exists in the building or the site, based on the radio signal; a determination part determining the decision on existence of the person every trigger timing being a timing defined based on the result of the detection of the sensor; an information generation part generating information related to the behavior of the person based on the decision on existence of the person determined at the trigger timing; and an information output part outputting the information generated by the information generation part.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-211156, filed on Oct. 27, 2015, the entire contents of which are incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a sensor system. 
       BACKGROUND 
       [0003]    A variety of sensor systems capable of grasping the behavior of people are proposed in the related art. 
         [0004]    For example, there has been proposed a residence monitoring system which is a sensor system which includes a radio slave unit which a resident always carries and a human detection sensor, and grasps the behavior of the residents and nonresidents. 
         [0005]    This residence monitoring system decides that a nonresident intrudes into a living room if a level of reception of a signal transmitted from the radio slave unit is lowered or there is a reaction in the human detection sensor. In addition, the residence monitoring system decides that the resident is not carrying the radio slave unit if there is no change in the level of reception of the signal transmitted from the radio slave unit even when there is a reaction in the human detection sensor. In addition, the residence monitoring system decides that an abnormality has occurred if the level of reception of the signal transmitted from the radio slave unit is high and there is no reaction in the human detection sensor. 
         [0006]    The above-described residence monitoring system is configured to include a human detection sensor installed in a living room. The installed human detection sensor may impair the aesthetic appearance of the living room. In addition, the installed human detection sensor may give a resident an impression that he/she is being monitored and the resident may feel uneasy about the human detection sensor. In other words, the installed human detection sensor may be unfavorable to the resident. 
         [0007]    In addition, the above-described residence monitoring system requires the resident to always carry the radio slave unit even in the living room, which may make the resident feel uncomfortable. 
       SUMMARY 
       [0008]    The present disclosure provides some embodiments of a sensor system which is capable of grasping the behavior of people without the use of a human detection sensor. 
         [0009]    According to one embodiment of the present disclosure, there is provided a sensor system including: a radio transmitting device configured to transmit a predetermined radio signal regularly; a sensor configured to detect opening/closing or locking/unlocking of a partition mechanism installed in a door of a building or a site; and an information processing device. The information processing device includes: a radio receiving part which receives the predetermined radio signal and a result of the detection of the sensor; a decision part which decides whether or not a person exists in the building or the site, based on the predetermined radio signal; a determination part which determines the decision on the existence of the person every trigger timing which is a timing defined based on the result of the detection of the sensor; an information generation part which generates information related to the behavior of the person based on the decision on the existence of the person determined at the trigger timing; and an information output part which outputs the information generated by the information generation part. 
         [0010]    In some embodiments, the trigger timing may be a timing at which a predetermined time elapses after the partition mechanism is closed or locked. 
         [0011]    In some embodiments, the predetermined time may be larger than two times and smaller than three times a transmission period of the predetermined radio signal. 
         [0012]    In some embodiments, after the second trigger timing, the information generation part may generate the information related to the behavior of the person based on a result of comparison between the decision on the existence of the person determined at the latest trigger timing and the decision on the existence of the person determined at the trigger timing earlier than the latest trigger timing. 
         [0013]    In some embodiments, the decision part may decide the existence of the person based on the reception strength of the predetermined radio signal. 
         [0014]    In some embodiments, the decision part may decide the existence of the person based on a lapse time after the radio receiving part receives the predetermined radio signal finally. 
         [0015]    In some embodiments, the predetermined radio signal may contain the unique identification information of the radio transmitting device, and the information processing device may include a correspondence relationship storage part which stores a correspondence relationship between the person and the unique identification information. 
         [0016]    In some embodiments, the number of radio transmitting devices may be two or more and the number of persons may be two or more. 
         [0017]    In some embodiments, one person corresponding to a plurality of unique identification information may be included in the two or more persons. 
         [0018]    According to another embodiment of the present disclosure, there is provided a sensor system including: a stationary sensor configured to detect take-out and return of an object to be managed; and a generation part configured to generate information related to the take-out and return of the object to be managed, based on a result of the detection of the stationary sensor. 
         [0019]    In some embodiments, the number of stationary sensors may be two or more and the number of objects to be managed may be two or more. The generation part may include: a receiving part which receives a result of the detection of the stationary sensor and the unique identification information of the stationary sensor; and a storage part which stores a correspondence relationship between the object to be managed and the unique identification information. 
         [0020]    In some embodiments, the object to be managed may be a common object used in common by a plurality of users. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a view schematically illustrating the configuration of a sensor system according to a first embodiment of the present disclosure. 
           [0022]      FIG. 2  is a view schematically illustrating the configuration of a radio transmitting device. 
           [0023]      FIG. 3  is a view schematically illustrating the configuration of an information processing device. 
           [0024]      FIG. 4  is a table showing a correspondence relationship between a sensor tag owner and sensor tag unique identification information. 
           [0025]      FIG. 5  is a table showing some of the data stored in a memory. 
           [0026]      FIG. 6  is a flow chart illustrating the operation of the information processing device. 
           [0027]      FIG. 7  is a table showing examples of contents of an e-mail. 
           [0028]      FIG. 8  is a time chart corresponding to contents (intruder warning) of the e-mail. 
           [0029]      FIG. 9  is a time chart corresponding to contents (Y returning home) of the e-mail. 
           [0030]      FIG. 10  is a time chart corresponding to contents (X going out) of the e-mail. 
           [0031]      FIG. 11  is a time chart corresponding to contents (no e-mail transmission) of the e-mail. 
           [0032]      FIG. 12  is a view schematically illustrating the configuration of a sensor system according to a second embodiment of the present disclosure. 
           [0033]      FIG. 13  is a view schematically illustrating the configuration of a return stand. 
           [0034]      FIG. 14  is a view schematically illustrating the configuration of an information processing device. 
       
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
       [0035]    The configuration of a sensor system according to a first embodiment will now be described with reference to  FIG. 1 .  FIG. 1  is a view schematically illustrating the configuration of a sensor system according to a first embodiment of the present disclosure. The sensor system according to this embodiment includes radio transmitting devices  1 A and  1 B for transmitting a predetermined radio signal regularly, an opening/closing detection sensor  2  for detecting the opening/closing of a door  101  installed in a doorway (entrance) of a house  100 , and an information processing device  3  for detecting whether or not each of the owners of the radio transmitting devices  1 A and  1 B is at home, based on the predetermined radio signal transmitted from the radio transmitting devices  1 A and  1 B. An example of the predetermined radio signal may include a radio signal such as Bluetooth® communication, Zigbee® communication, specific small power radio, or the like. 
         [0036]    The radio transmitting devices  1 A and  1 B are one example of a “radio transmitting device” described in the claim. The opening/closing detection sensor  2  is one example of a  “ sensor” described in the claim. The information processing device  3  is one example of an “information processing device” described in the claim. 
         [0037]    Each of the radio transmitting devices  1 A and  1 B is a device attached to a thing which is necessarily carried by an owner without special circumstances when the owner is to go out. Although the thing which is necessarily carried by an owner without special circumstances (e.g., carrying forgotten, etc.) when the owner is to go out is illustrated with a key in  FIG. 1 , the thing may be a wallet, shoes, a bag, clothing. etc. In addition, as described above, since the information processing device  3  detects whether or not an owner of each of the radio transmitting devices  1 A and  1 B is at home, based on the predetermined radio signal transmitted from the radio transmitting devices  1 A and  1 B, each of the radio transmitting devices  1 A and  1 B acts as a sensor for detecting whether or not the owner is at home. If the same function as the radio transmitting device  1 A can be realized by a smartphone  4 A and the owner of the radio transmitting device  1 A necessarily carries the smartphone  4 A without special circumstances when going out, the smartphone  4 A may be utilized as a substitute for the RF transmitting device IA. 
         [0038]    For this reason, the radio transmitting devices  1 A and  1 B may be referred to as a sensor tag  1 A and a sensor tag  1 B, respectively. In the following description, the sensor tag  1 A and the sensor tag  1 B may be simply referred to as a sensor tag  1  when it is not necessary to distinguish between them. In addition, in the following description, the owner of the sensor tag  1 A is assumed as a resident X residing in the house  100  and the owner of the sensor tag  1 B is assumed as a resident Y residing in the house  100 . The sensor tag  1  may be, e.g., of a label type different from that shown in  FIG. 1 , i.e., of a type attached to a carried thing such as a wallet, shoes, a bag, clothing, etc. by pasting. When the sensor tag I is of a label type, there is an advantage in that the sensor tag  1  can be easily attached to the carried thing. 
         [0039]    As one example of the opening/closing detection sensor  2 , there may be a magnet sensor used to detect opening/closing of the door  101  by detecting a magnet attached to the door  101  in a state where the door  101  is closed but does not detect the magnet in a state where the door  101  is opened. As another example, there may be a contact sensor used to detect the opening/closing of the door  101  by contact with the door  101  in a state where the door  101  is closed but does not contact with the door  101  in a state where the door  101  is opened. 
         [0040]    In addition, unlike this embodiment, a sensor to detect locking/unlocking of the door  101  may be used instead of the opening/closing detection sensor  2 . In this case, the present embodiment may be applied by regarding the unlocked state of the door  101  as the opened state of the door  101  in the present embodiment and regarding the locked state of the door  101  as the closed state of the door  101  in the present embodiment. 
         [0041]    The information processing device  3  outputs information related to behaviors of the resident X and the resident Y. In the present embodiment, the information processing device  3  outputs the information related to behaviors of the resident X and the resident Y in an e-mail format (the format of the output is not limited thereto), to the smartphone  4 A possessed by the resident X and the smartphone  4 B possessed by the resident Y via a communication network (not shown). 
         [0042]    As one example of the information processing device  3 , a general purpose gateway may be used. As another example, a USB (Universal Serial Bus) receiver (a small mobile receiver with a USB port) connected to a USB terminal of the existing personal computer may be used. 
         [0043]    Next, the configuration of the sensor tag  1  will be described with reference to  FIG. 2 .  FIG. 2  is a view schematically illustrating the configuration of the sensor tag  1 . The sensor tag  1  includes an environmental power generating device  11 , a power IC  12 , a power storage device  13 , a control microcomputer  14  and a radio communication part  15 . 
         [0044]    The environmental power generating device  11  is a device which collects energy from the surrounding environments and converts the collected energy into power, such as a solar cell for converting solar energy into power, a bimorph structured with two piezoelectric plates bonded to each other for converting a displacement (mechanical energy) caused by an applied force into power, a thermoelectric device for converting heat energy into power, a vibration power generating device for converting vibration energy into power, etc. Although only one environmental power generating device  11  is shown in  FIG. 2 , two or more environmental power generating devices  11  may be installed. In this case, these environmental power generating devices  11  may be of the same type or of different types. In some embodiments, a solar cell used as the environmental power generating device  11  may be of a flexible shape, such as an organic thin film solar cell or the like. 
         [0045]    The power IC  12  stores a surplus of power generated in the environmental power generating device  11  in the power storage device  13 . The power storage device  13  may be, e.g., a secondary battery or a condenser. The power IC  12  converts generated power of the environmental power generating device  11  or discharged power of the power storage device  13  into stabilized power of a predetermined voltage and supplies the stabilized power to the control microcomputer  14  and the radio communication part  15 . In addition, a primary battery may be used instead of or in addition to the environmental power generating device  11  and the power storage device  13 . 
         [0046]    The control microcomputer  14  stores unique identification information (e.g., a serial number or the like) of the sensor tag  1  in an internal memory in a nonvolatile manner. The control microcomputer  14  transmits a predetermined radio signal superimposed with the unique identification information of the sensor tag  1  to the radio communication part  15  regularly. 
         [0047]    Next, the configuration of the information processing device  3  will be described with reference to  FIG. 3 .  FIG. 3  is a view schematically illustrating the configuration of the information processing device  3 . The information processing device  3  includes a power IC  31 , a control part  32 , a memory  33 , an e-mail transmitting part  34  and a radio communication part  35 . The control part  32 , the memory  33  and a portion of the e-mail transmitting part  34  (e.g., a portion except a connector for connecting to a communication network) may be implemented with, e.g., a microcomputer. The radio communication part  35  has the function to receive a predetermined radio signal transmitted from the sensor tag  1  and the function to receive a result of detection of the opening/closing detection sensor  2  wirelessly. Correspondingly, the opening/closing detection sensor  2  includes a radio transmitting part for transmitting the result of detection of the opening/closing detection sensor  2  wirelessly and a power part (e.g., a primary battery and a power converting part for converting output power of the primary battery into stabilized power) for supplying power to the opening/closing detection sensor  2  and the radio transmitting part. 
         [0048]    In addition, the opening/closing detection sensor  2  and the information processing device  3  may be connected by a wire and a signal corresponding to the result of detection of the opening/closing detection sensor  2  may be transmitted to the control part  32  via a signal line. In this case, the radio communication part  35  may not have the function to receive the result of detection of the opening/closing detection sensor  2  wirelessly. Here, when using the wired connection of the opening/closing detection sensor  2  with the information processing device  3  to supply DC power from the information processing device  3  to the opening/closing detection sensor  2 , transmitting the result of detection of the opening/closing detection sensor  2  in a high frequency signal, and superimposing the DC power on the high frequency signal, the opening/closing detection sensor  2  and the information processing device  3  may be connected by a single signal line. Further, the power part included in the opening/closing detection sensor  2  for supplying power to the opening/closing detection sensor  2  may include the environmental power generating device. 
         [0049]    The control part  32  is one example of a “decision part,” “determination part” and “information generation part” described in the claims. The memory  33  is one example of a “correspondence relationship storage part” described in the claims. The e-mail transmitting part  34  is one example of an “information output part” described in the claims. The radio communication part  35  is one example of a “radio receiving part” described in the claims. 
         [0050]    The power IC  31  converts input power (e.g., commercial AC power) into stabilized power with a predetermined voltage value and supplies the stabilized power to the control part  32  and the radio communication part  35 . 
         [0051]    The control part  32  generates and outputs information related to behaviors of the resident X and the resident Y according to a program and data stored in the memory  33  in a nonvolatile manner. Specifically, the control part  32  generates the information related to behaviors of the resident X and the resident Y based on a result of reception in the radio communication part  35  and instructs the e-mail transmitting part  34  to output the information related to behaviors of the resident X and the resident Y to the smartphones  4 A and  4 B. 
         [0052]    The memory  33  stores a correspondence relationship between the owner of a sensor tag and the unique identification information of the sensor tag. In this embodiment, as shown in  FIG. 4 , the resident X and the unique identification information of the sensor tag  1 A are associated with each other and the resident Y and the unique identification information of the sensor tag  1 B are associated with each other. The information processing device  3  includes an input part (not shown) and may be configured to rewrite the correspondence relationship between the owner of the sensor tag and the unique identification information of the sensor tag, stored in the memory  33 , based on data input to the input part. 
         [0053]    In addition, unlike this embodiment, when the resident X owns the sensor tag  1 A, a sensor tag for wallet and a sensor tag for shoes, unique identification information of these three sensor tags and the resident X may be stored in the memory  33  in association. In this case, this embodiment may be applied by considering the reception strength of the sensor tag  1 A to be equal to or lower than a threshold TH if at least one of the reception strengths of the three sensor tags is equal to or lower than the threshold TH and considering the reception strength of the sensor tag  1 A to exceed the threshold TH if all of reception strengths of the three sensor tags exceed the threshold TH. 
         [0054]    The memory  33  also stores “indoor state,” “latest state,” “final reception time” and “final door closing time” in a nonvolatile manner, as shown in  FIG. 5 . In this embodiment, the “indoor state” refers to a state where the resident X is at home or is not present and the resident Y is at home or is absent and the “latest state” also refers to a state where the resident X is at home or is not present and the resident Y is at home or is not present. In addition, in this embodiment, the “final reception time” refers to two cases, i.e., time at which a predetermined radio signal transmitted from the sensor tag  1 A is finally received, and a time at which a predetermined radio signal transmitted from the sensor tag  1 B is finally received. In addition, in this embodiment, the “final door closing time” refers to a time at which the door  101  is finally closed. 
         [0055]    Next, the operation of the information processing device  3  will be described with reference to  FIG. 6 .  FIG. 6  is a flow chart illustrating the operation of the information processing device  3 . 
         [0056]    When the starting of the information processing device  3  is completed, the control part  32  determines whether or not each of the residents X and Y is at home, based on the reception strength of a signal received by the radio communication part  35 , of the predetermined radio signals from the sensor tags  1 A and  1 B, and stores a result of the determination, as the indoor state, in the memory  33  (Step S 10 ). 
         [0057]    In this embodiment, if the reception strength of the predetermined radio signal from the sensor tag  1 A exceeds the threshold TH, it is determined that the resident X is at home. Otherwise (i.e., if the reception strength is equal to or lower than the threshold TH or the radio signal cannot be received), it is determined that the resident X is not present. In addition, if the reception strength of the predetermined radio signal from the sensor tag  1 B exceeds the threshold TH, it is determined that the resident Y is at home. Otherwise (i.e., if the reception strength is equal to or lower than the threshold TH or the radio signal cannot be received), it is determined that the resident Y is not present. Therefore, the threshold TH may be set such that the reception strength exceeds the threshold TH when the sensor tag  1  is brought to a place in the house  100  where the sensor tag  1  is likely to be placed and the reception strength is equal to or lower than the threshold TH or the radio signal cannot be received when the sensor tag  1  is brought out of the house  100 . Thus, a resident may not always carry the sensor tag  1  in the house  100 . Further, in some embodiments, the reception strength may exceed the threshold TH wherever the sensor tag  1  is brought in the house  100 . Thus, a restriction on a place in the house  100  where the sensor tag  1  is to be placed is eliminated. 
         [0058]    In addition, instead of Step S 10 , the state of the resident X and Y may be set arbitrarily. Even in this case, the state is corrected to a correct state after a while by a loop of S 20  to S 50  to be described later. However, in this case, since it is assumed that there is a reception of the predetermined radio signals from the sensor tags  1 A and  1 B at the point of time when the state of the resident X and Y is set arbitrarily, the process proceeds to Step S 20 . 
         [0059]    At Step S 20 , the control part  32  determines whether or not at least one of the predetermined radio signals from the sensor tags  1 A and  1 B has been received by the radio communication part  35 . If it is determined that no radio signal is received (NO in Step S 20 ), the process proceeds to Step S 30 . If it is determined that at least one is received (YES in Step S 20 ), the process proceeds to Step S 40 . 
         [0060]    At Step S 30 , the control part  32  determines whether or not a predetermined time has elapsed after the predetermined radio signals from the sensor tags  1 A and  1 B were finally received. If it is determined that a predetermined time has elapsed after at least one was finally received (YES in Step S 30 ), the process proceeds to Step S 40 . If it is determined that a predetermined time has not elapsed after all were finally received (NO in Step S 30 ), the process proceeds to Step S 50 . 
         [0061]    At Step S 40 , the control part  32  creates or updates the latest state according to the following process. If the reception strength of the predetermined radio signal from the sensor tag  1 A exceeds the threshold TH, it is assumed that the resident X is at home. If the reception strength of the predetermined radio signal from the sensor tag  1 A is equal to or lower than the threshold TH, it is assumed that the resident X is not present. If the reception strength of the predetermined radio signal from the sensor tag  1 B exceeds the threshold TH, it is assumed that the resident Y is at home. If the reception strength of the predetermined radio signal from the sensor tag  1 B is equal to or lower than the threshold TH, it is assumed that the resident Y is not present. If the predetermined time has elapsed after the predetermined radio signal from the sensor tag  1 A was finally received, it is assumed that the resident X is not present. If the predetermined time has elapsed after the predetermined radio signal from the sensor tag  1 B was finally received, it is assumed that the resident Y is not present. 
         [0062]    The predetermined time used in Step S 30  may be larger than two times and smaller than three times the transmission period of the predetermined radio signal transmitted from the sensor tag  1 . By setting the predetermined time to be larger than two times the transmission period, the process can be prevented from proceeding from Step S 30  to Step S 40  even though the radio signal is not received accidentally once due to a sudden radio interference or the like, thereby preventing the latest state from being incorrect. In addition, by setting the predetermined time to be smaller than three times (2.5 times in some embodiments) the transmission period, the proceeding of Step S 30  to Step S 40  can be prevented from being excessively delayed. In addition, the predetermined time used in Step S 30  may be the same as or different from a predetermined time used in Step S 50  to be described later. 
         [0063]    At Step S 50 , the control part  32  determines whether or not a predetermined time has elapsed after the door  101  was closed (i.e., from the point of time when an opening/closing state of the door  101  is changed from an opened state to a closed state), based on a result of detection of the opening/closing detection sensor  2 . If it is determined that a predetermined time has not elapsed, (NO in Step S 50 ), the process returns to Step S 20 . If it is determined that a predetermined time has elapsed, (YES in Step S 50 ), the process proceeds to Step S 60 . Timings (TT 1  and TT 2  in  FIGS. 8 to 11 ) at which the predetermined time has elapsed after the door  101  was closed are one example of “trigger timing” described in the claim. 
         [0064]    The predetermined time (PT in  FIGS. 8 to 11 ) used in Step S 50  may be larger than two times and smaller than three times the transmission period (P in  FIGS. 8 to 11 ) of the predetermined radio signal transmitted from the sensor tag  1 . By setting the predetermined time to be larger than two times the transmission period, after the predetermined radio signal is transmitted twice or more from the sensor tag  1  after the door  101  is closed, the process proceeds to Step S 60  in which the latest state is determined. Therefore, it is possible to avoid the latest state from being determined based on a state of being not received accidentally once due to a sudden radio interference or the like after the door  101  is closed and it is possible to prevent the latest state from being incorrect. In addition, by setting the predetermined time to be smaller than three times (2.5 times in some embodiments) the transmission period, Step S 60  can be performed without being excessively delayed. In addition, in a case where a state of being not received accidentally once due to a sudden radio interference or the like after the door  101  is closed hardly ever occurs, the predetermined time (PT in  FIGS. 8 to 11 ) used in Step S 50  may be set to be equal to the transmission period (P in  FIGS. 8 to 11 ) of the predetermined radio signal transmitted from the sensor tag  1 . However, if the threshold TH is set to be high in setting the predetermined time (PT in  FIGS. 8 to 11 ) used in Step S 50  to be equal to the transmission period (P in  FIGS. 8 to 11 ) of the predetermined radio signal transmitted from the sensor tag  1 , the reception strength of a predetermined radio signal from a sensor tag carried by the resident may exceed the threshold TH when a resident is out of the house  100  but is yet near the house  100  immediately after the door  101  is closed. Therefore, when the threshold TH is set to be high, the predetermined time (PT in  FIGS. 8 to 11 ) used in Step S 50  may be set to be slightly longer than the transmission period (P in  FIGS. 8 to 11 ) of the predetermined radio signal transmitted from the sensor tag  1 . Thus, since the time at which a resident goes away from the house  100  until the time at which the predetermined time (PT in  FIGS. 8 to 11 ) has elapsed after the door  101  was closed can be sufficiently secured, the latest state determined at the timing at which the predetermined time (PT in  FIGS. 8 to 11 ) has elapsed after the door  101  was closed can be set with a correct content stating that “there is no resident who has a sensor tag and is out of the house  100 .” The setting of the predetermined time (PT in  FIGS. 8 to 11 ) used in Step S 50  to be equal to the transmission period (P in  FIGS. 8 to 11 ) of the predetermined radio signal transmitted from the sensor tag  1  and the setting of the predetermined time (PT in  FIGS. 8 to 11 ) used in Step S 50  to be slightly longer than the transmission period (P in  FIGS. 8 to 11 ) of the predetermined radio signal transmitted from the sensor tag  1  may also be applied to a relationship between the predetermined time used in Step S 30  and the transmission period of the predetermined radio signal transmitted from the sensor tag  1 . In other words, the predetermined time used in Step S 30  may be set to be equal to the transmission period of the predetermined radio signal transmitted from the sensor tag  1  and the predetermined time used in Step S 30  may be set to be slightly longer the transmission period of the predetermined radio signal transmitted from the sensor tag  1 . 
         [0065]    At Step S 60 , the control part  32  compares the indoor state and the latest state for the sensor tag  1 A and compares the indoor state and the latest state for the sensor tag  1 B. 
         [0066]    Thereafter, the control part  32  determines the contents (the information related to behaviors of the resident X and the resident Y) of the e-mail based on a result of the comparison in Step S 60  and instructs the e-mail transmitting part  34  to transmit the e-mail (Step S 70 ). Then, after the transmission of the e-mail, the control part  32  stores the latest state, as the indoor state, in the memory  33  (Step S 80 ). Thus, the latest state disappears immediately after the process of Step S 80 . Then, the process returns to Step S 20  after the process of Step S 80 . 
         [0067]      FIG. 7  is a table showing examples of the contents of the e-mail determined in Step S 70 .  FIGS. 8 to 11  are time charts corresponding to the contents of the e-mail. In  FIGS. 8 to 11 , the reception strength when a predetermined radio signal is transmitted by the sensor tag  1  but is not received by the information processing device  3  is x-marked. 
         [0068]      FIG. 8  shows a situation where the indoor state determined at the trigger timing TT 1  is “both (the residents X and Y) not present” and, thereafter, the latest state determined at the trigger timing TT 2  though the door  101  is opened/closed once is also “both (the residents X and Y) not present.” In this case, there is a high possibility that a person other than the residents X and Y intrudes into the house  100  when the door  101  is opened/closed immediately before the trigger timing TT 2 . Therefore, the contents of the e-mail are set to “intruder warning.” 
         [0069]      FIG. 9  shows a situation where the indoor state determined at the trigger timing TT 1  is “ resident X at home and resident Y not present” and, thereafter, the latest state determined at the trigger timing TT 2  when the door  101  is opened/closed once is “resident X at home and resident Y at home.” In this case, the resident Y is moving into the house  100  from the outside of the house  100  when the door  101  is opened/closed immediately before the trigger timing TT 2 . Therefore, the contents of the e-mail are set to “resident Y returning home.” In addition, in this case, since the resident Y understands his own behavior, the transmission destination of the e-mail may be set to be only the smartphone  4 A rather than both the smartphones  4 A and  4 B. In other words, according to the contents (the information related to behaviors of the residents X and B) of the e-mail, the transmission destination of the corresponding information may be changed. In addition, a modification may be considered where no e-mail is transmitted based on the idea that home returning of the resident Y can be easily grasped since the resident X is at home. 
         [0070]      FIG. 10  shows a situation where the indoor state determined at the trigger timing TT 1  is “ resident X at home and resident Y not present” and, thereafter, the latest state determined at the trigger timing TT 2  when the door  101  is opened/closed once is “resident X not present and resident Y not present.” In this case, the resident X is moving to the outside of the house  100  from the inside of the house  100  when the door  101  is opened/closed immediately before the trigger timing TT 2 . Therefore, the contents of the e-mail are set to “resident X going out.” In addition, in this case, since the resident X understands his own behavior, the transmission destination of the e-mail may be set to be only the smartphone  4 B rather than both the smartphones  4 A and  4 B. 
         [0071]      FIG. 11  shows a situation where the indoor state determined at the trigger timing TT 1  is “ resident X at home and resident Y at home” and, thereafter, the latest state determined at the trigger timing TT 2  when the door  101  is opened/closed once is “resident X at home and resident Y at home.” In this case, it may be assumed that the resident Y makes a visitor correspondence around the door  101  in the house  100  in a period of an opened state of the door  101  that occurred immediately before the trigger timing TT 2 . Information related to behaviors of the residents in such a case where at least one of the residents is at home and the residents do not go in/out is not transmitted to the smartphones  4 A and  413 , 
         [0072]    As described above, the sensor system according to the present embodiment determines whether the residents X and Y are at home or not present, based on the predetermined radio signal transmitted from the sensor tag  1 , and the determination is made every trigger timings TT 1  and TT 2  determined according to a result of detection of the opening/closing detection sensor  2 . Therefore, it is possible to grasp human behaviors without any human detection sensor. 
         [0073]    In addition, in the present embodiment, the indoor state and the latest state are compared in Step S 60 , and the contents (information related to behaviors of the residents X and Y) of the e-mail are determined based on a result of the comparison. However, the contents (information related to behaviors of the residents X and Y) of the e-mail may be determined based on only the latest state. However, in this modification, for example in a case where the resident X is at home in the latest state, it may be unclear whether the resident X returned home when the door  101  was opened/closed immediately before the trigger timing TT 2  or whether the resident X returned home when the door  101  was opened/closed previously and the resident X was already at home when the door  101  was opened/closed immediately before the trigger timing TT 2 . 
       Second Embodiment 
       [0074]      FIG. 12  is a view schematically illustrating the configuration of a sensor system according to a second embodiment of the present disclosure. The sensor system according to the second embodiment includes return stands  5 A and  5 B, each of which contains a key detection sensor  58  (see  FIG. 13  to be described later), and an information processing device  9  which generates information related to take-out and return of keys  7 A and  7 B based on a result of detection of the key detection sensor  58 . The return stands  5 A and  5 B are placed for use in a predetermined place. 
         [0075]    The key detection sensor  58  is one example of a “stationary sensor” described in the claims, and the information processing device  9  is one example of “generation part” described in the claims. 
         [0076]    The return stand  5 A is provided to return a warehouse key  6 A, and the return stand  5 B is provided to return a company car key  6 B. The warehouse key  6 A and the company car key  6 B are common objects used in common by a plurality of users. In the following description, the return stands  5 A and  5 B are simply referred to as a return stand  5  when it is not necessary to distinguish between them. In addition, in the following description, the warehouse key  6 A and the company car key  6 B are simply referred to as a key  6  when it is not necessary to distinguish between them. 
         [0077]    The return stand  5  includes a disc-like base  51  and a pole  52  extending vertically from the center of the base  51 . A solar cell  53  is installed in the lower side (toward the base  51 ) of the pole  52 . In a case where the solar cell  53  has a curved shape along the periphery of the pole  52  as in this embodiment, an organic thin film solar cell or the like may be used. In addition, for example, in a case where a solar cell installation portion of the pole  52  has a planar shape unlike this embodiment, a flat solar cell may be used. 
         [0078]    The key detection sensor  58  (see  FIG. 13  to be described later) is contained in the base  51 . In this embodiment, a magnet sensor for detecting the proximity of a magnet is used as the key detection sensor  58 . A magnet ring  8  is connected to the key  6  via a key ring  7 . An inner diameter of the magnet ring  8  is determined such that the pole  52  passes through the magnet ring  8 . When the key  6  is returned, the magnet ring  8  contacts the base  51  and the key detection sensor  58  detects the proximity of the magnet. In other words, the key detection sensor  58  does not detect the proximity of the magnet when the key  6  is taken out, and the key detection sensor  58  detects the proximity of the magnet when the key  6  is returned. In addition, unlike this embodiment, for example, instead of the magnet sensor, a contact sensor may be used as the key detection sensor  58 . 
         [0079]    A label or the like indicating that the return stand  5 A is a warehouse key return stand (e.g., a label described with a “warehouse key”) may be attached to the base  51  of the return stand  5 A. Similarly, a label or the like indicating that the return stand  5 B is a company car key return stand (e.g., a label described with a “company car key”) may be attached to the base  51  of the return stand  5 B. Instead of or in addition to the attachment of the label, the return stand  5 A and the return stand  5 B may differ from each other in shape in order to know which return stand corresponds to which key. 
         [0080]      FIG. 13  is a view schematically illustrating the configuration of the return stand  5 . The return stand  5  includes a solar cell  53 , a power IC  54 , a power storage device  55 , a control microcomputer  56 , a radio communication part  57  and a key detection sensor  58 . 
         [0081]    The power IC  54  stores a surplus of power generated in the solar cell  53  in the power storage device  55 . The power storage device  55  may be, e.g., a secondary battery, a condenser or the like. The power IC  54  converts generated power of the solar cell  53  or discharged power of the power storage device  55  into a stabilized power of a predetermined voltage and supplies the stabilized power to the control microcomputer  56  and the radio communication part  57 . In addition, a primary battery may be used instead of or in addition to the solar cell  53  and the power storage device  55 . 
         [0082]    The control microcomputer  56  stores unique identification information (e.g., a serial number or the like) of the return stand  5  in an internal memory in a nonvolatile manner. In addition, the control microcomputer  56  supplies power to the key detection sensor  58  and receives a result of detection of the key detection sensor  58 . The control microcomputer  56  transmits to the radio communication part  57  a predetermined radio signal superimposed with the result of detection of the key detection sensor  58  and the unique identification information of the return stand  5 , with a change in the result of detection of the key detection sensor  58  (a change from proximity detection to proximity non-detection of a magnet or a change from proximity non-detection to proximity detection of the magnet) as a trigger. An example of the predetermined radio signal may include a radio signal such as Bluetooth® communication, Zigbee® communication, specific small power radio, or the like. 
         [0083]      FIG. 14  is a view schematically illustrating the configuration of the information processing device  9 . The information processing device  9  includes a power IC  91 , a control part  92 , a memory  93  and a radio communication part  94 . The control part  92  and the memory  93  may be implemented with, e.g., a microcomputer. The radio communication part  94  has the function to receive a predetermined radio signal transmitted from the sensor tag  1 . The memory  93  is one example of a “storage part” described in the claims. The radio communication part  94  is one example of a “receiving part” described in the claims. 
         [0084]    The power IC  91  converts input power (e.g., commercial AC power) into stabilized power of a predetermined voltage value and supplies the stabilized power to the control part  92  and the radio communication part  94 . 
         [0085]    The control part  92  generates information related to take-out and return of the key  6  based on a result of detection of the key detection sensor  58 , according to a program and data stored in the memory  93  in a nonvolatile manner. Specifically, the control part  92  generates the information related to take-out and return of the keys  6 A and  6 B based on a result of reception in the radio communication part  94 . In addition, the control part  92  may transmit the generated information to an external server, a mobile device or the like. 
         [0086]    The memory  93  stores a correspondence relationship between the type of the key  6  and the unique identification information of the return stand  5 . The information processing device  9  includes an input part (not shown), and may be configured to rewrite the correspondence relationship between the type of the key  6  and the unique identification information of the return stand  5 , stored in the memory  93 , based on data input to the input part. 
         [0087]    As described above, the sensor system according to the present embodiment generates the information related to take-out and return of the key  6  based on a result of detection of the key detection sensor  58 . Therefore, it is possible to grasp human behaviors (operation of take-out and return of the key  6 ) without any human detection sensor. 
       Other Modifications 
       [0088]    In addition to the above embodiments, the present disclosure can be modified in various ways without departing from the spirit and scope of the disclosure. 
         [0089]    For example, as a modification of the first embodiment, instead of the door  101  of the house  100 , a door of a warehouse, an entry/exit door of a room of an office building or a door of a school may be used. 
         [0090]    As another modification of the first embodiment, the information processing device  3  and other devices may be used in combination. For example, the information processing device  3  and an emergency button may be used in combination. In this case, when the emergency button is pushed, the information processing device  3  may transmit an e-mail reporting a state of emergency to all residents. As another example, the information processing device  3  and lighting equipment may be used in combination. In this case, the information processing device  3  may automatically turn off the lighting equipment when all residents are not present and may automatically turn on the lighting equipment when at least one of the residents returns home. As another example, when the information processing device  3  and the lighting equipment are used in combination, the information processing device  3  may transmit an intruder warning by e-mail while intimidating an intruder by blinking the lighting equipment. 
         [0091]    As another modification of the first embodiment, the number of sensor tags  1  may be one. In this case, information related to behavior of one resident is generated and output. In addition, in this case, for example, if a user of the sensor system has grasped a person who carries the sensor tag  1  at the time of going out, the unique identification information of the sensor tag  1  may not be superimposed on a predetermined radio signal. 
         [0092]    As another modification of the first embodiment, when the latest state is updated in Step S 40 , it may be determined that a problem such as power shortage or the like has occurred in the sensor tag  1 A in a case where the state of the resident X is changed from “at home” to “not present” though the opening/closing of the door  101  is not detected by the opening/closing detection sensor  2  after the last trigger timing, and a result of the determination may be reflected on the contents of an e-mail. Similarly, when the latest state is updated in Step S 40 , it may be determined that a problem such as power shortage or the like has occurred in the sensor tag  1  in a case where the state of the resident Y is changed from “at home” to “not present” though the opening/closing of the door  101  is not detected by the opening/closing detection sensor  2  after the last trigger timing, and a result of the determination may be reflected on the contents of an e-mail. In addition, in a case where a result of detection of the opening/closing detection sensor  2  cannot be acquired in Step S 50 , it may be determined that a problem such as power shortage or the like has occurred in the opening/closing detection sensor  2 , and a result of the determination may be reflected on the contents of an e-mail. 
         [0093]    As a modification of the second embodiment, the information processing device  9  and other devices may be used in combination. For example, the information processing device  9  and a take-out reservation database system may be used in combination. In this case, the information processing device  9  may detect an unreserved take-out and transmit an instruction signal to the return stand  5  in which the unreserved take-out is made such that a warning is reported from the return stand  5  in which the unreserved take-out is made. 
         [0094]    As another modification of the second embodiment, the number of key detection sensors  58  may be one. In this case, the unique identification information of the return stand  5  may not be superimposed on a predetermined radio signal. 
         [0095]    As another modification of the second embodiment, the return stand  5  and the information processing device  9  may be connected by a wire, and a signal corresponding to the result of detection of the key detection sensor  58  may be transmitted to the control part  92  via a signal line. In this case, the radio communication parts  57  and  94  may be replaced with an interface for wired connection. Here, when using the wired connection of the return stand  5  and the information processing device  9  to supply DC power from the information processing device  9  to the return stand  5 , transmitting the result of detection of the key detection sensor  58  in a high frequency signal, and superimposing the DC power on the high frequency signal, the return stand  5  and the information processing device  9  may be connected by a single signal line. 
       INDUSTRIAL APPLICABILITY 
       [0096]    The present disclosure can be utilized as, e.g., a sensor system for detecting “at home” and a sensor system for detecting the removal of a common object. 
         [0097]    According to the present disclosure in some embodiments, it is possible to provide a sensor system which is capable of grasping behaviors of persons without any human detection sensor. 
         [0098]    While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the novel methods and apparatuses described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.