JP5945778B2 - Sensor system and sensor tag - Google Patents

Description

The present invention relates to a sensor system and a sensor tag .

As a sensor system, for example, a sensor system that measures the state of a measurement target portion set on a measurement target such as a concrete structure or soil is known (see, for example, Patent Document 1).
For example, the sensor system described in Patent Document 1 has a plurality of sensors that measure the state of road equipment and a roadside unit installed in the vicinity of the plurality of sensors, and the roadside unit wirelessly transmits measurement information of each sensor. The collected measurement information is collected by communication or wired communication, and the collected measurement information is transmitted to an in-vehicle unit mounted on the inspection vehicle by wireless communication.

Conventionally, in such a sensor system, each sensor performs measurement and transmission of the measurement result at regular time intervals. By setting such a long time interval, measurement can be performed over a long period of time using the power of the power source embedded in the measurement object together with the sensor.
However, in the conventional sensor system, since the time interval is not changed, there is a problem that detailed measurement information cannot be obtained at a short time interval, for example, at the time of the earthquake or within a desired period thereafter.

JP 2010-117837 A

  An object of the present invention is to provide a sensor system capable of measuring the state of a measurement target portion of a measurement target over a long period of time and acquiring detailed measurement information at a short time interval within a desired period. .

Such an object is achieved by the present invention described below.
The sensor system of the present invention is a sensor tag having a sensor for measuring a state of a measurement target part of a measurement target, and a communication unit having a function of wirelessly transmitting measurement information of the sensor,
A reader / writer having a function of receiving measurement information wirelessly transmitted from the communication unit;
The sensor tag includes a first state in which the communication unit wirelessly transmits measurement information of the sensor at a first transmission time interval, and a second transmission time in which the communication unit is shorter than the first transmission time interval. It is configured to be switchable between a second state in which measurement information of the sensor is wirelessly transmitted at intervals,
In the first state, the communication unit performs carrier sense at a first carrier sense time interval, and in the second state, the communication unit is a second carrier shorter than the first carrier sense time interval. Carrier sensing is performed at sense time intervals.
According to the sensor system configured as described above, the state of the measurement target portion of the measurement target can be measured over a long period of time, and detailed measurement information can be acquired at short time intervals within a desired period.

In the sensor system of the present invention, the sensor tag includes a storage unit in which a plurality of programs including a first program used for the first state and a second program used for the second state are stored in advance. It is preferable that a control unit that selects one of the plurality of programs stored in the storage unit and controls driving of the communication unit based on the selected program is provided.
Thereby, the 1st state and 2nd state of a communication part can be switched.

In the sensor system of the present invention, the reader / writer further has a function of wirelessly transmitting instruction information for selecting one of the plurality of programs,
The communication unit further has a function of receiving the instruction information,
It is preferable that the control unit selects one program from the plurality of programs stored in the storage unit based on the instruction information.
Thereby, the first state and the second state of the communication unit can be switched by an instruction from the outside of the measurement object.

In the sensor system of the present invention, the reader / writer stores in advance a plurality of instruction information including instruction information for selecting the first program and instruction information for selecting the second program, It is preferable that one instruction information out of the plurality of instruction information is selected and wirelessly transmitted based on the environment information of the measurement object.
Thereby, according to the environment of a measurement object, the 1st state and 2nd state of a communication part can be switched.

In the sensor system of the present invention, it is preferable that the sensor tag includes a time information generation unit that generates time information.
Thereby, carrier sense can be performed based on the time information of the time information generation unit.
In the sensor system of the present invention, it is preferable that the time information generating unit is configured using a transmitter having a clock frequency lower than 32 kHz.
Thereby, the power consumption of the sensor tag can be suppressed.

In the sensor system of the present invention, the reader / writer further has a function of generating time information,
In the first state, the sensor tag preferably performs measurement at a time interval based on time information generated by the reader / writer, and the communication unit transmits measurement information at a time interval based on time information generated by the reader / writer.
Thereby, it is not necessary for the sensor tag to have a real-time clock, and the power consumption of the sensor tag can be suppressed.

In the sensor system of the present invention, it is preferable that the reader / writer has a transmitter having a clock frequency of 32 kHz or more.
Accordingly, the sensor can perform measurement and the communication unit can transmit measurement information at a highly accurate time interval.
In the sensor system of the present invention, the sensor tag performs measurement at a first measurement time interval in the first state, and the sensor performs the first measurement time in the second state. It is preferable to perform measurement at a second measurement time interval shorter than the interval.
Thereby, detailed measurement information can be acquired within a desired period.

In the sensor system of the present invention, it is preferable that the wireless transmission of the communication unit uses an LF band carrier wave.
Thereby, even if the measurement object is, for example, a concrete structure, it is possible to increase the communicable distance between the sensor tag and the reader / writer while suppressing the power consumption of the sensor tag.

In the sensor system of the present invention, it is preferable that the reader / writer further has a function of wirelessly transmitting the received measurement information.
Thereby, the measurement information collected by the reader / writer can be easily acquired by the host.
In the sensor system of the present invention, it is preferable that the wireless transmission of the reader / writer uses an RF band carrier wave.
Thereby, the communicable distance between the host and the reader / writer can be increased.
In the sensor system of the present invention, it is preferable that the measurement object is a concrete structure.
Thereby, the state of a concrete structure can be measured.

It is a figure which shows an example of the use condition of the sensor system which concerns on embodiment of this invention. It is a block diagram which shows schematic structure of the sensor system shown in FIG. It is a schematic diagram which shows the installation state of the sensor tag of the sensor system shown in FIG. It is a block diagram which shows the sensor tag structure shown in FIG. It is a block diagram which shows schematic structure of the reader / writer of the sensor system shown in FIG. It is a flowchart for demonstrating operation | movement of the sensor system shown in FIG.

Hereinafter, a preferred embodiment of a sensor system of the present invention will be described with reference to the accompanying drawings.
1 is a diagram illustrating an example of a usage state of a sensor system according to an embodiment of the present invention, FIG. 2 is a block diagram illustrating a schematic configuration of the sensor system illustrated in FIG. 1, and FIG. 3 is a sensor system illustrated in FIG. FIG. 4 is a block diagram showing the sensor tag configuration shown in FIG. 3, FIG. 5 is a block diagram showing a schematic configuration of the reader / writer of the sensor system shown in FIG. 2, and FIG. These are flowcharts for demonstrating operation | movement of the sensor system shown in FIG.

Hereinafter, a case where the sensor system of the present invention is used for quality measurement of a concrete structure will be described as an example.
A sensor system 1 shown in FIG. 1 measures the quality of a concrete structure 100 constituting a bridge.
The concrete structure 100 is not limited to a bridge. For example, tunnels, dams, buildings such as buildings and houses, harbor structures such as seawalls, river structures, airport facilities such as runways, etc. It can also be applied to structures. In addition, the measurement target of the sensor system 1 is not limited to the concrete structure, and may be soil that forms a bank, a bank, a slope, or the like, for example.

The sensor system 1 includes a plurality of sensor tags 2 embedded in the concrete structure 100 and a reader / writer 3 installed outside the concrete structure 100.
In the example illustrated in FIG. 1, the plurality of sensor tags 2 include a plurality of sensor tags 2 a, 2 b, and 2 c embedded in the bridge girder portion 101 of the concrete structure 100 and a plurality of sensor tags 2 embedded in the pier portion 102 of the concrete structure 100. Sensor tags 2d and 2e.

Here, the sensor tags 2a, 2b, 2c, 2d, and 2e have the same configuration except that the installation positions are different. Therefore, in the following description, the sensor tag 2a will be representatively described, and description of the sensor tags 2b, 2c, 2d, and 2e will be omitted. In FIG. 2, the sensor tags 2c, 2b, 2d, and 2e are not shown. The number of sensor tags 2 is not limited to that shown in FIG.
In such a sensor system 1, as shown in FIG. 2, the reader / writer 3 and each sensor tag 2 are configured to be capable of wireless communication with each other.

  Note that only one sensor tag 2 of the plurality of sensor tags 2 may be configured to be capable of wireless communication with the reader / writer 3. In this case, the sensor tag 2 capable of wireless communication with the reader / writer 3 collects the measurement information of the other sensor tags 2 by putting the sensor tags 2 in wireless communication with each other, and collects the collected measurement information. And wirelessly transmit to the reader / writer 3.

Further, the reader / writer 3 is configured to be capable of wireless communication with the host 4, and the measurement information collected by the reader / writer 3 is transmitted to the host 4 (server).
Here, the host 4 may be fixedly installed in a structure away from the concrete structure 100 as long as it is within a distance communicable with the reader / writer 3 when necessary, or the inspection vehicle (the movement shown in FIG. 1). It may be mounted on the body M). Moreover, the host 4 may be comprised with the portable terminal.

  The host 4 further has a function of acquiring environmental information of the concrete structure 100 and wirelessly transmitting the environmental information. The wirelessly transmitted environment information is received by the reader / writer 3. Then, the reader / writer 3 gives an instruction to each sensor tag 2 based on the received environment information. Here, the host 4 constitutes environmental information acquisition means for acquiring environmental information of the concrete structure 100.

Such environmental information is not particularly limited as long as it relates to the presence or absence of an environmental state in which the state measurement of the concrete structure 100 needs to be performed at short time intervals. For example, the presence or absence of a disaster such as an earthquake or a tsunami can be mentioned. .
In addition, the method for acquiring environmental information in the host 4 is not particularly limited. For example, the host 4 includes a sensor that detects the presence or absence of a disaster or the like, and acquires environmental information based on the detection result of the sensor. Alternatively, it may be acquired from outside by wired or wireless.

Hereinafter, each part which comprises the sensor system 1 is demonstrated sequentially.
(Sensor tag)
As shown in FIG. 3, the sensor tag 2 is embedded in the vicinity of the reinforcing bar 104 in the concrete 103 of the concrete structure 100 that is a measurement object. When the concrete structure 100 is placed, the sensor tag 2 may be fixedly embedded in the reinforcing bar 104 before the concrete 103 is placed, or may be embedded in the hardened concrete 103 after the placement. .
As shown in FIG. 4, the sensor tag 2 includes sensors 21 and 22, a communication unit 23, an interface unit 24, a storage unit 25, a time information generation unit 26, a control unit 27, and a power supply unit 28. Have.

[sensor]
Each of the sensors 21 and 22 measures a state of a measurement target portion (hereinafter also simply referred to as “measurement target portion”) set in the vicinity of the reinforcing bar 104 of the concrete 103.
Specifically, the sensor 21 is a pH sensor that measures pH as the state of the measurement target site. Thereby, based on the measurement information of the sensor 21, the corrosion state of the reinforcing bar 104 can be measured.

In this embodiment, the sensor 21 is installed between the outer surface of the concrete 103 and the reinforcing bar 104. Therefore, the sensor 21 can detect the neutralization of the concrete 103, the intrusion of chloride ions into the concrete 103, and the like before the reinforcing bar 104 reaches corrosion. Thereby, the measure which prevents the corrosion of the rebar 104 by neutralization of the concrete 103, the penetration | invasion of the chloride ion to the concrete 103, etc. can be taken beforehand at an appropriate time.
The pH sensor is not particularly limited, and various known pH sensors can be used. For example, the pH sensor has a metal electrical resistor or electrode pair, and electrical characteristics associated with corrosion of the electrical resistor or electrode. A sensor that measures pH based on the change can be used.
More specifically, as such a pH sensor, for example, a resistance value that accompanies corrosion of an electrical resistor, a sensor that measures pH based on changes in impedance, and the impedance between electrode pairs that accompanies corrosion of electrode pairs, A sensor or the like that measures pH based on changes in potential difference, capacitance, inductance, or the like can be used.

The sensor 22 is a strain sensor that measures strain as the state of the first measurement target region. Thereby, based on the measurement information of the sensor 22, the distortion state of the concrete 103 or the reinforcing bar 104 can be measured.
In the present embodiment, the sensor 22 is installed along the reinforcing bar 104. Thereby, the distortion state of the reinforcing bar 104 can be measured with high sensitivity.
Such a strain sensor is not particularly limited, and various known strain sensors can be used. For example, a strain sensor using an electric resistor whose resistance value changes due to an external force, a semiconductor strain sensor using a semiconductor, or the like is used. be able to.

[Communication Department]
The communication unit 23 has a wireless communication function.
More specifically, the communication unit 23 has a function of wirelessly transmitting the measurement information of the sensors 21 and 22 described above. The wirelessly transmitted measurement information is received by the reader / writer 3 as will be described in detail later.
The communication unit 23 further has a function of receiving instruction information wirelessly transmitted from the reader / writer 3. Based on the received instruction information, the control unit 27 selects and executes a program in the storage unit 25.

  Further, the communication unit 23 may further have a function of receiving time information wirelessly transmitted from the reader / writer 3. In this case, the received time information can be used for time correction of the time information generation unit 26. Thereby, the operation | movement of the sensor tag 2 and the reader / writer 3 can be synchronized easily and reliably by adjusting the time of the time information generation part 26 and the reader / writer 3. Therefore, the sensor tag 2 can be operated without waste, and the power consumption of the sensor tag 2 can be suppressed.

Such a communication unit 23 includes an antenna 231 and a communication circuit 232.
The antenna 231 is not particularly limited. For example, the antenna 231 is made of a metal material, carbon, or the like, and has a form such as a winding or a thin film. The antenna 231 may be configured with one antenna in common for transmission and reception, or may be configured with two antennas corresponding to transmission and reception, respectively.

The communication circuit 232 includes, for example, a transmission circuit for transmitting an electromagnetic wave, a modulation circuit having a function for modulating a signal to be transmitted, a reception circuit for receiving an electromagnetic wave, and a demodulation having a function for demodulating a received signal. Circuit. Note that the communication circuit 232 includes a down converter circuit having a function of converting a signal frequency to a low level, an up converter circuit having a function of converting a signal frequency to a high level, an amplifier circuit having a function of amplifying a signal, and the like. Also good. Note that these circuits may be provided on the same substrate or different substrates.
The communication unit 23 is not particularly limited as long as wireless communication within the concrete structure 100 is possible, but a communication unit using a carrier wave in the LF band (30 kHz to 300 kHz) is preferable. Thereby, the communication distance between the sensor tag 2 and the reader / writer 3 can be increased while suppressing the power consumption of the sensor tag 2.

[Interface part]
The interface unit 24 has a function of inputting the measurement information of the sensors 21 and 22 described above to the control unit 27.
Further, the interface unit 24 performs a predetermined process on the measurement information of the sensors 21 and 22 as necessary, and then inputs the processed measurement information to the control unit 27. For example, the interface unit 24 includes an A / D conversion circuit, converts measurement information of the sensors 21 and 22 from analog to digital, and inputs the converted information to the control unit 27. The interface unit 24 includes an amplifier circuit, and amplifies the measurement information of the sensors 21 and 22 and inputs the amplified information to the control unit 27.

[Storage unit]
The storage unit 25 stores in advance a plurality of programs including a first program used for a first state of the communication unit 23 to be described later and a second program used for a second state of the communication unit 23 to be described later. Yes.
Of these programs, one of these programs is appropriately selected and executed by the control unit 27 described later.

  Here, the first program is, for example, a program used in normal times, and is for measuring the sensors 21 and 22 and transmitting the measurement results while suppressing the power consumption of the sensor tag 2. The second program is a program used at the time of an earthquake and a predetermined period thereafter, for example, for measuring the sensors 21 and 22 and transmitting the measurement results at short time intervals.

The storage unit 25 may have a function of storing measurement information of the sensors 21 and 22. In this case, the stored information is wirelessly transmitted by the communication unit 23 described above. Thereby, whenever the communication part 23 performs the measurement by the sensors 21 and 22 several times, a communication operation | movement can be performed and the measurement information of multiple times can be collectively transmitted by radio.
Such a storage unit 25 is not particularly limited, and any of a non-volatile memory and a volatile memory can be used. However, it is possible to maintain a state in which information is stored without supplying power, thereby saving power. It is preferable to use a non-volatile memory from the viewpoint that the memory can be realized, and it is particularly preferable to use a flash memory from the viewpoint that information can be read and written with power saving.

[Time information generator]
The time information generation unit 26 has a function of generating time information (clock signal). Accordingly, the communication unit 23 can perform carrier sense based on the time information of the time information generation unit 26.
The time information generation unit 26 is not particularly limited, and is constituted by, for example, an oscillation circuit using a crystal resonator. Thereby, the time information generation unit 26 can generate time information with relatively low power consumption.

  The time information generation unit 26 is preferably configured using a transmitter having a clock frequency lower than that of the transmitter used for the time information generation unit 34 of the reader / writer 3 to be described later, specifically, from 32 kHz. It is preferable to use a low clock frequency oscillator (oscillator circuit). Thereby, the power consumption of the sensor tag 2 can be suppressed. Note that the time information of the time information generation unit 26 need only be used for measuring the time interval of carrier sense, and therefore does not need to be highly accurate.

[Control unit]
The control unit 27 has a function of controlling each unit constituting the sensor tag 2, specifically, the communication unit 23, the interface unit 24, the storage unit 25, the time information generation unit 26, and the like.
Specifically, the control unit 27 has a function of selecting one program among a plurality of programs stored in the storage unit 25 and controlling the driving of the communication unit 23 based on the selected program. Have.

Thereby, the sensor tag 2 has a first state in which the communication unit 23 wirelessly transmits the measurement information of the sensors 21 and 22 at the first transmission time interval T11 (hereinafter, also simply referred to as “first state”), It is possible to switch between the second state in which the communication unit 23 wirelessly transmits the measurement information of the sensors 21 and 22 at the second transmission time interval T12 that is shorter than the first transmission time interval T11.
In the first state, the communication unit 23 performs carrier sense at the first carrier sense time interval T21, and in the second state, the communication unit 23 performs the second carrier sense shorter than the first carrier sense time interval T21. Carrier sense is performed at time interval T22.

By appropriately switching between the first state and the second state, the state of the measurement target portion of the concrete structure 100 can be measured over a long period (specifically, 20 years or more), and a desired period ( For example, detailed measurement information can be acquired at short time intervals within the earthquake disaster and a predetermined period thereafter.
Further, the control unit 27 selects one program from among a plurality of programs stored in the storage unit 25 based on the instruction information received by the communication unit 23, that is, the instruction information from the reader / writer 3. Thereby, according to the instruction | indication from the exterior of the concrete structure 100, the 1st state and 2nd state of the communication part 23 of the sensor tag 2 can be switched.

In addition, the control unit 27 drives and controls the sensors 21 and 22 so that the measurement time interval of the sensors 21 and 22 in the second state is shorter than the measurement time interval of the sensors 21 and 22 in the first state. . That is, in the sensor tag 2, in the first state, the sensors 21 and 22 perform measurement at the first measurement time interval T31, and in the second state, the sensor 21 and 22 operate from the first measurement time interval T31. The measurement is performed at the second measurement time interval T32 that is shorter. Thereby, more detailed measurement information can be acquired within a desired period (that is, the period of the second state).
Although this control part 27 is not specifically limited, For example, it is comprised by MPU.

[Power supply part]
The power supply unit 28 is not particularly limited as long as it can supply power capable of operating the sensor tag 2. For example, a battery such as a button-type battery can be used, and in particular, the battery operating life is relatively long. From this point of view, it is preferable to use a lithium battery.
In the sensor tag 2 configured as described above, the communication circuit 232, the interface unit 24, the storage unit 25, the time information generation unit 26, and the control unit 27 of the communication unit 23 constitute an electric circuit 41.

  In addition, the communication unit 23, the interface unit 24, the storage unit 25, the time information generation unit 26, the control unit 27, and the power supply unit 28 are sealed with a sealing unit 42. Thereby, when the sensor tag 2 is installed in the presence of moisture or concrete, the deterioration of the communication unit 23, the interface unit 24, the storage unit 25, the time information generation unit 26, the control unit 27, and the power supply unit 28 is prevented. Can do.

Here, the sensors 21 and 22 are exposed to the outside of the sealing portion 42. Thereby, measurement by the sensors 21 and 22 can be performed while the sealing part 42 prevents deterioration of each part other than the sensors 21 and 22.
As a constituent material of the sealing portion 42, a known sealing resin can be used. For example, a thermoplastic resin such as an acrylic resin, a urethane resin, and an olefin resin, an epoxy resin, a melamine resin, Various resin materials such as a thermosetting resin such as a phenolic resin can be used, and one or more of these can be used in combination.

(Reader / writer)
Next, the reader / writer 3 will be described in detail.
As illustrated in FIG. 5, the reader / writer 3 includes a tag side communication unit 31, a host side communication unit 32, a storage unit 33, a time information generation unit 34, a control unit 35, and a power supply unit 36.

[Tag side communication section]
The tag side communication part 31 can be comprised similarly to the communication part 23 of the sensor tag 2 mentioned above.
However, the tag side communication part 31 can abbreviate | omit the function which transmits measurement information.
More specifically, the tag side communication unit 31 has a function of receiving measurement information wirelessly transmitted from the communication unit 23 of the sensor tag 2 described above. As will be described later in detail, the received measurement information is stored in the storage unit 33 and then wirelessly transmitted from the host side communication unit 32 at a predetermined time.

The tag-side communication unit 31 further has a function of wirelessly transmitting instruction information for selecting one of a plurality of programs stored in the storage unit 25 of the sensor tag 2. This wirelessly transmitted instruction information is received by the communication unit 23 of the sensor tag 2.
The tag side communication unit 31 may further have a function of wirelessly transmitting the time information generated from the time information generation unit 34. In this case, the wirelessly transmitted time information is received by the sensor tag 2 and can be used to correct the time of the time information generation unit 26 of the sensor tag 2.

Such a tag side communication unit 31 includes an antenna 311 and a communication circuit 312.
The antenna 311 can be configured similarly to the antenna 231 of the sensor tag 2 described above.
The communication circuit 312 can be configured similarly to the communication circuit 232 of the sensor tag 2 described above.

[Host side communication section]
The host side communication unit 32 has a function of transmitting the measurement information (more specifically, measurement information and time information stored in the storage unit 33) received by the tag side communication unit 31 described above. The transmitted measurement information is received by the host 4 as will be described in detail later.
Thereby, the measurement information collected by the reader / writer 3 can be easily acquired by the host 4.

The host-side communication unit 32 further has a function of receiving environment information wirelessly transmitted from the host 4. The received environment information is received by the reader / writer 3.
The host-side communication unit 32 can be configured in the same manner as the communication unit 23 of the sensor tag 2 described above, but transmits wirelessly using a carrier wave having a frequency higher than the LF band (for example, a GHz band) because it transmits in the air. It is preferable to be configured so as to perform radio transmission using a carrier wave in the RF band, and it is more preferable.

When the wireless transmission of the reader / writer 3 uses an RF band carrier wave, the communicable distance between the host 4 and the reader / writer 3 can be increased.
Note that the host-side communication unit 32 can omit the function of receiving measurement information and the function of transmitting and receiving time information.
Such a host-side communication unit 32 includes an antenna 321 and a communication circuit 322.

The antenna 321 can be configured in the same manner as the antenna 231 of the sensor tag 2 described above, but is preferably configured so that the host-side communication unit 32 can transmit a carrier wave in the RF band.
The communication circuit 322 can be configured in the same manner as the communication circuit 232 of the sensor tag 2 described above, but is preferably configured so that the host-side communication unit 32 can transmit a carrier wave in the RF band.

[Storage unit]
The storage unit 33 has a function of storing measurement information received by the tag side communication unit 31. The stored information is wirelessly transmitted by the host side communication unit 32 described above.
Here, the storage unit 33 stores measurement information of the sensors 21 and 22 together with the time information generated by the time information generation unit 34. That is, the storage unit 33 stores the measurement information of the sensors 21 and 22 with the time information added to the measurement information of the sensors 21 and 22. By using such measurement information, the state of the measurement target part can be known for each time.

In addition, the storage unit 33 indicates instruction information (first instruction information) for selecting the first program used for the first state and instruction information for selecting the second program used for the second state. A plurality of instruction information including (second instruction information) is stored in advance. The stored instruction information is wirelessly transmitted by the tag side communication unit 31.
Such a memory | storage part 33 can be comprised similarly to the memory | storage part 25 of the sensor tag 2 mentioned above. Further, as will be described later, since the power supply unit 36 of the reader / writer 3 can be a battery having a relatively large capacity, a commercial power supply, a secondary battery connected to a solar battery, or the like, the storage unit 33 is relatively consumed. You may be comprised with the memory with big electric power.

[Time information generator]
The time information generation unit 34 can be configured in the same manner as the time information generation unit 26 of the sensor tag 2 described above, and has a function of generating time information (clock signal).
In addition, as will be described later, a battery with a relatively large capacity, a commercial power supply, a secondary battery connected to a solar battery, or the like can be used as the power supply unit 36 of the reader / writer 3. A device that can generate more accurate time information, for example, an atomic oscillator, a GPS, a device that acquires time information using a standard radio wave, or the like can be used even if the power consumption is high. When the host side communication unit 32 has a function of receiving time information, the host side communication unit 32 receives time information from the host 4 and corrects the time of the time information generation unit 34 based on the time information. You can also

In addition, the time information of the time information generation unit 34 is used to measure time intervals (T11, T31) in which the sensors 21 and 22 in the first state perform measurement and the communication unit 23 transmits measurement information. Further, such time information is added to the measurement information.
Such a time information generator 34 preferably includes a transmitter having a clock frequency of 32 kHz or more. Thereby, the sensors 21 and 22 can perform measurement and the communication unit 23 can transmit measurement information at a highly accurate time interval.

[Control unit]
The control unit 35 has a function of controlling each unit constituting the reader / writer 3, specifically, the tag side communication unit 31, the host side communication unit 32, the storage unit 33, the time information generation unit 34, and the like.
Further, the control unit 35 selects one instruction information from among a plurality of instruction information stored in the storage unit 33 based on the environmental information from the host 4 and causes the tag side communication unit 31 to wirelessly transmit the instruction information. Thereby, according to the environment of the concrete structure 100, the 1st state and 2nd state of the communication part 23 of the sensor tag 2 can be switched.

Further, in the first state, the control unit 35 measures time according to the time information of the time information generation unit 34 and periodically (specifically, corresponds to the first measurement time interval and the first transmission time interval). The tag side communication unit 31 is operated at a time interval. As a result, in the sensor tag 2, in the first state, the sensors 21 and 22 perform measurement at the time interval based on the time information generated by the time information generation unit 34 of the reader / writer 3, and the communication unit 23 measures the measurement information. Send. Therefore, it is not necessary for the sensor tag 2 to have a real-time clock, and the power consumption of the sensor tag 2 can be suppressed.
Although this control part 35 is not specifically limited, For example, it is comprised by MPU.
The operation of the control unit 35 will be described in detail in the description of the operation of the sensor system 1 described later.

[Power supply part]
The power supply unit 36 can be configured in the same manner as the power supply unit 28 of the sensor tag 2 described above, and supplies power that can operate the reader / writer 3.
However, since the reader / writer 3 can be installed outside the concrete structure 100, the power source 36 is easy to inspect, repair, replace, etc. and is larger than the power source 28 of the sensor tag 2. Can be used. In addition, it is possible to supply power to the power supply unit 36 from the outside by wire without drilling the concrete structure 100 or the like.
For this reason, as the power source unit 36, a power source that generates larger power than the power source unit 28 of the sensor tag 2, for example, a battery having a relatively large capacity, a commercial power source, or a solar cell connected to the power source unit 36. A secondary battery or the like can be used. By using such a power source, the communication distance between the tag side communication unit 31 and the host side communication unit 32 described above can be increased.

(Sensor system operation)
Next, the operation of the sensor system 1 will be described based on FIG.
In the sensor system 1 of the present embodiment, first, the sensor tag 2 enters the first state in which the communication unit 23 wirelessly transmits the measurement information of the sensors 21 and 22 at the first transmission time interval T11. The communication unit 23 switches to the second state in which the measurement information of the sensors 21 and 22 is wirelessly transmitted at the second transmission time interval T12 that is shorter than the first transmission time interval T11.

Hereinafter, the first state and the second state will be sequentially described in detail.
[First state]
In the first state, the sensor tag 2 waits for an instruction from the reader / writer 3 while performing carrier sense at the first carrier sense time interval T21.
On the other hand, the reader / writer 3 performs the instruction information (more specifically, the first information described above) at a predetermined cycle (first transmission time interval T11 and first measurement time interval T31) according to the time information of the time information generation unit 34. 1 instruction) is transmitted.

Thereby, in the first state, the sensor tag 2 performs the measurement by the sensors 21 and 22 (hereinafter also simply referred to as “measurement”) at the first measurement time interval T31, and transmits the measurement information by the communication unit 23 ( Hereinafter, this is also simply referred to as “transmission”) at the first transmission time interval T11.
When any of such measurement and transmission is performed, the control unit 27 of the sensor tag 2 becomes active, and the power consumption of the control unit 27 increases. On the other hand, when neither measurement nor transmission is performed, the control unit 27 enters a sleep state, and the power consumption of the control unit 27 is reduced.

In the present embodiment, the first transmission time interval T11 is set equal to the first measurement time interval T31. Thereby, transmission performed at the first transmission time interval T11 is performed after each measurement performed at the first measurement time interval T31.
Note that the first transmission time interval T11 may be set longer than the first measurement time interval T31. In this case, the first transmission time interval T11 is preferably an integral multiple of the first measurement time interval T31. Thereby, each transmission can be performed every predetermined number of measurements.

The first transmission time interval T11 and the first measurement time interval T31 are set to be equal intervals in the example shown in FIG. 6, but may not be equal intervals, and the intervals are variable. It may be. When the first transmission time interval T11 and the first measurement time interval T31 are variable, for example, these time intervals are usually about once per day, and the amount of change in measurement information is a predetermined value or less. 1 time / 10 days.
Specifically, the first transmission time interval T11 and the first measurement time interval T31 are set to about 1/10 days to 1 time / 1 day, respectively.

Further, the first carrier sense time interval T21 is set shorter than the first transmission time interval T11 and the first measurement time interval T31 described above, and specifically, is set to several times / one second. Yes.
In the first state as described above, the first transmission time interval T11, the first carrier sense time interval T21, and the first measurement time interval T31 are set to be relatively long. Power consumption can be reduced.

[Second state]
As described above, in the first state, the sensor tag 2 is waiting for an instruction from the reader / writer 3 while performing carrier sense at the first carrier sense time interval T21. The reader / writer 3 transmits instruction information (more specifically, an instruction to select the second program described above) based on the environment information.
Accordingly, the sensor tag 2 enters the second state, performs measurement at the second measurement time interval T32, and performs transmission at the second transmission time interval T12.

In the second state, the sensor tag 2 waits for an instruction from the reader / writer 3 while performing carrier sense at the second carrier sense time interval T22. As a result, the reader / writer 3 can give an instruction to the sensor tag 2 at a more accurate timing. As a result, more detailed measurement information can be acquired.
In the present embodiment, the second transmission time interval T12 is set equal to the second measurement time interval T32. Thereby, the transmission performed at the second transmission time interval T12 is performed every time after the measurement performed at the second measurement time interval T32.

Note that the second transmission time interval T12 may be set longer than the second measurement time interval T32. In this case, the second transmission time interval T12 is preferably an integral multiple of the second measurement time interval T32. Thereby, each transmission can be performed every predetermined number of measurements.
Note that the second transmission time interval T12 and the second measurement time interval T32 may be set at equal intervals or may not be equal intervals, and the intervals may be varied as necessary. There may be.

The second transmission time interval T12 and the second measurement time interval T32 are not particularly limited as long as they are shorter than the first transmission time interval T11 and the first measurement time interval T31. Time / second to about once / day.
The second carrier sense time interval T22 is not particularly limited as long as the second carrier sense time interval T22 is set shorter than the first carrier sense time interval T21 described above. For example, the second carrier sense time interval T22 is set to about several times per second.

In the second state as described above, since the second transmission time interval T12 and the second measurement time interval T32 are set to be relatively short, detailed measurement information can be acquired at short time intervals. it can.
In particular, in the second state, since the second carrier sense time interval T22 is set shorter than the first carrier sense time interval T21, more detailed measurement information can be acquired.

As mentioned above, although the sensor system of this invention was demonstrated based on embodiment of illustration, this invention is not limited to this.
For example, in the sensor system of the present invention, the configuration of each part can be replaced with any configuration that exhibits the same function, and any configuration can be added.
Moreover, although embodiment mentioned above demonstrated to the example the case where each sensor tag was an active tag, it is not limited to this, Each sensor tag may be a passive tag.

  In the above-described embodiment, the case where two sensors are provided in one sensor tag has been described as an example. However, the number of sensors provided in one sensor tag may be one, There may be three or more. When a plurality of sensors are provided in one sensor tag, the plurality of sensors may be the same type or different types.

Further, the arrangement of the sensors can be appropriately set according to the type and purpose of the sensor.
The type of sensor is not limited to that of the above-described embodiment, and may be, for example, a chloride ion sensor, a temperature sensor, a magnetic sensor, an acceleration sensor, an optical sensor, a pressure sensor, or the like.

1 sensor system 2 sensor tag 2a sensor tag 2b sensor tag 2c sensor tag 2d sensor tag 2e sensor tag 3 reader writer 4 host 21 sensor 22 Sensor 23 Communication unit 24 Interface unit 25 Storage unit 26 Time information generation unit 27 Control unit 28 Power supply unit 31 Tag side communication unit 32 Host side communication unit 33 ··· Storage unit 34 ··· Time information generation unit 35 ··· Control unit 36 · · · Power supply unit 41 · · · Electrical circuit 42 · · · Sealing unit 100 · · · Concrete structure 101 · · · Bridge girder unit 102 · · · Bridge pier 103 ··· Concrete 104 ... Reinforcing bar 231 ... Antenna 232 ... Communication circuit 311 ... Antenna 312 ... Communication circuit 321 Antenna 322 Communication circuit M Mobile unit T11 First transmission time interval T12 Second transmission time interval T21 First carrier sense time interval T22 Second carrier sense time interval T31 ... First measurement time interval T32 ... Second measurement time interval

Claims (15)

1st to nth sensor tags (n is an integer of 2 or more) having a sensor for measuring the state of a measurement target part of a measurement target and a communication unit having a function of wirelessly transmitting measurement information of the sensor ;
A reader / writer having a function of receiving measurement information wirelessly transmitted from the communication unit,
The first to nth sensor tags are configured to be able to communicate with each other wirelessly,
The first to n-th sensor tags are in a first state in which the sensor performs measurement at a first measurement time interval and the communication unit wirelessly transmits measurement information of the sensor at a first transmission time interval. A second state in which the sensor performs measurement at a second measurement time interval and the communication unit wirelessly transmits measurement information of the sensor at a second transmission time interval that is shorter than the first transmission time interval; Is configured to be switchable,
The first transmission time interval is an integer multiple of the first measurement time interval;
In the first state, the communication unit performs carrier sense at a first carrier sense time interval, and in the second state, the communication unit is a second carrier shorter than the first carrier sense time interval. the carrier sense are performed by the sense time interval,
The first sensor tag among the first to n-th sensor tags communicates with the reader / writer, and the first sensor tag and the second to n-th sensor tags communicate with each other, thereby One sensor tag collects the measurement information, and the measurement information collected by the first sensor tag is wirelessly transmitted to the reader / writer .   The sensor system according to claim 1, wherein the second transmission time interval is an integral multiple of the second measurement time interval.   The sensor tag is stored in a storage unit in which a plurality of programs including a first program used in the first state and a second program used in the second state are stored in advance, and in the storage unit. 3. The sensor system according to claim 1, further comprising: a control unit that selects one program from the plurality of programs and controls driving of the communication unit based on the selected program. The reader / writer further has a function of wirelessly transmitting instruction information for selecting one of the plurality of programs,
The communication unit further has a function of receiving the instruction information,
The sensor system according to claim 3, wherein the control unit selects one program from the plurality of programs stored in the storage unit based on the instruction information.   The reader / writer stores in advance a plurality of instruction information including instruction information for selecting the first program and instruction information for selecting the second program, and environmental information of the measurement object The sensor system according to claim 4, wherein one instruction information out of the plurality of instruction information is selected and wirelessly transmitted based on the information.   The sensor system according to claim 1, wherein the sensor tag includes a time information generation unit that generates time information.   The sensor system according to claim 6, wherein the time information generation unit is configured using an oscillator having a clock frequency lower than 32 kHz. The reader / writer further has a function of generating time information,
8. The sensor tag according to claim 1, wherein, in the first state, the sensor performs measurement and the communication unit transmits measurement information at time intervals based on time information generated by the reader / writer. The sensor system according to any one of the above.   The sensor system according to claim 8, wherein the reader / writer includes a transmitter having a clock frequency of 32 kHz or more.   In the first state, the sensor tag performs measurement at a first measurement time interval, and in the second state, the sensor tag has a second shorter than the first measurement time interval. The sensor system according to claim 1, wherein measurement is performed at measurement time intervals.   The sensor system according to claim 1, wherein the wireless transmission of the communication unit uses a carrier wave in an LF band.   The sensor system according to claim 1, wherein the reader / writer further has a function of wirelessly transmitting received measurement information.   The sensor system according to claim 12, wherein the wireless transmission of the reader / writer uses a carrier wave in an RF band.   The sensor system according to claim 1, wherein the measurement object is a concrete structure. First to nth sensor tags (n is an integer of 2 or more) having a sensor for measuring the state of a measurement target part of a measurement target and a communication unit having a function of wirelessly transmitting measurement information of the sensor to a reader / writer ) And
The first to n-th sensor tags are in a first state in which the sensor performs measurement at a first measurement time interval and the communication unit wirelessly transmits measurement information of the sensor at a first transmission time interval. A second state in which the sensor performs measurement at a second measurement time interval and the communication unit wirelessly transmits measurement information of the sensor at a second transmission time interval that is shorter than the first transmission time interval; Is configured to be switchable,
The first transmission time interval is an integer multiple of the first measurement time interval;
In the first state, the communication unit performs carrier sense at a first carrier sense time interval, and in the second state, the communication unit is a second carrier shorter than the first carrier sense time interval. the carrier sense are performed by the sense time interval,
Of the first to n-th sensor tags, the first sensor tag communicates with the reader / writer, and the first sensor tag and the second to n-th sensor tags communicate with each other. A sensor tag, wherein the first sensor tag collects the measurement information and wirelessly transmits the measurement information collected by the first sensor tag to the reader / writer .

Images