Reading system

Abstract

This system provides a reading system that can reliably receive sensor signals using multiple reading devices. [Solution] The reading system includes a sensor device installed on a structure and having a capacitor capable of storing power for driving, and a plurality of reading devices that transmit a wireless signal capable of charging the capacitor and receive a sensor signal from the sensor device, the plurality of reading devices mounted on a mobile body that moves along the structure, each reading device having an antenna and a transmitting / receiving unit that transmits the wireless signal and receives the sensor signal via the antenna, and the plurality of transmitting / receiving units of the plurality of reading devices transmit the wireless signal and receive the sensor signal at frequencies that are spaced apart so that their output does not stop even when they perform carrier sensing on each other.

Description

Technical Field

[0001] The present disclosure relates to a reading system.

Background Art

[0002] Conventionally, a sensor device for detecting loosening and vibration of a rail fastening device that fastens a rail to a sleeper, and a battery-less type RFID (Radio Frequency Identifier) tag that transmits a sensor signal representing measurement data are installed in the rail fastening device, and a plurality of readers mounted along the traveling direction on a train receive the sensor signal to read measurement data (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the conventional inspection system does not stipulate the relationship between the frequencies of a plurality of readers. For this reason, when carrier sense is performed between a plurality of readers, there is a period during which all readers or some readers cannot transmit a read signal, the sensor device cannot be sufficiently charged and measurement data cannot be obtained, and there is a risk that none of the readers can receive the sensor signal.

[0005] In addition, when carrier sense is performed between a plurality of readers, there is a period during which all readers or some readers cannot receive the sensor signal, and even if the sensor device measures, there is a risk that none of the readers can receive the sensor signal.

[0006] Therefore, an object is to provide a reading system that can surely receive a sensor signal using a plurality of reading devices. [Means for solving the problem]

[0007] The reading system of the embodiment of the present disclosure includes a sensor device having a capacitor capable of storing power for driving and installed on a structure, and a plurality of reading devices that transmit a wireless signal capable of charging the capacitor and receive a sensor signal from the sensor device, the plurality of reading devices mounted on a moving body that moves along the structure, each reading device having an antenna and a transmitting / receiving unit that transmits the wireless signal and receives the sensor signal via the antenna, and the plurality of transmitting / receiving units of the plurality of reading devices transmit the wireless signal and receive the sensor signal at frequencies that are spaced apart so as not to perform carrier sensing with each other. [Effects of the Invention]

[0008] By using multiple reading devices, a reading system capable of reliably receiving sensor signals can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the configuration of the reading system in the embodiment. [Figure 2] This figure shows an example of a specific configuration of the sensor device of the reading system according to the embodiment. [Figure 3] This figure shows an example of the time variation of the charge level of the capacitor in the sensor device of the reading system of the embodiment. [Figure 4A] This is a characteristic diagram showing an example of experimental results (Part 1). [Figure 4B] This figure shows an example of a communication status log when the experimental results (Part 1) were obtained. [Figure 5A] This is a characteristic diagram showing an example of experimental results (Part 2). [Figure 5B] This is a characteristic diagram showing an example of experimental results (Part 2). [Figure 5C] This is a characteristic diagram showing an example of experimental results (Part 2). [Modes for carrying out the invention]

[0010] The following describes embodiments applying the reading system of this disclosure.

[0011] The following explains the XYZ coordinate system. The directions parallel to the X-axis (X direction), the directions parallel to the Y-axis (Y direction), and the directions parallel to the Z-axis (Z direction) are mutually orthogonal. Plane view refers to viewing from the XY plane. In addition, the lengths, widths, thicknesses, etc. of each part may be exaggerated in the following explanation to make the structure easier to understand.

[0012] <Embodiment> Figure 1 shows an example of the configuration of the reading system 100 of the embodiment. The reading system 100 includes a sensor device 110, reading devices 120A to 120C, and a control device 130. Figure 1 shows three reading devices 120A to 120C as an example. Since the configurations of reading devices 120A to 120C are equivalent to each other as an example, they will simply be referred to as reading device 120 unless specifically distinguished.

[0013] Figure 1 shows the reading system 100, the inner wall of the tunnel 10, and the train 50. The inner wall of the tunnel 10 is an example of a structure, and the train 50 is an example of a moving object.

[0014] In Figure 1, the XY plane is, for example, a horizontal plane. The +Z direction is vertically upward. For example, the inner wall 10 of the tunnel extends along the Y direction, and the direction of travel of the train 50 is the +Y direction.

[0015] Multiple sensor devices 110 are installed, for example, along the inner wall 10 of the tunnel, and multiple reading devices 120 are mounted on the train 50 along the direction of travel (+Y direction). The train 50 is also equipped with a control device 130, which is connected to the reading devices 120A to 120C.

[0016] <Overview of Sensor Device 110 and Structures, etc.> The sensor device 110, as an example, detects the fastening force of the structure fastening part on the inner wall 10 of the tunnel. The structure fastening part, as an example, is bolts, nuts, etc. provided in a fixing part for fixing a power cable or the like to the inner wall 10 of the tunnel, and the fastening force is the fastening force of bolts, nuts, etc. The sensor device 110, as an example, is a washer-type sensor fastened to the fixing part together with such bolts and nuts. By detecting the fastening force with the washer-type sensor device 110 and monitoring its change with the reading system 100, loosening of bolts, nuts, etc. in the fixing part for fixing a power cable or the like to the inner wall 10 of the tunnel can be discovered. In FIG. 1, only a partial section in the extending direction (Y direction) of the tunnel is shown, and three sensor devices 110 are shown. As an example, a large number of sensor devices 110 are provided at equal intervals along the inner wall 10 of the tunnel.

[0017] The sensor device 110 is a passive type sensor device, does not include a secondary battery, and does not receive power supply from a commercial power supply or the like. Therefore, there is no need to connect a cable or the like for power supply to the sensor device 110. Also, since the sensor device 110 transmits a sensor signal to the reading device 120 by wireless communication with the reading device 120, there is no need to connect a cable or the like for extracting the sensor signal.

[0018] When the train 50 moves, the reading system 100 transmits a reading signal from a plurality of reading devices 120 to a plurality of sensor devices 110. Each sensor device 110 charges an internal capacitor with the reading signal, performs measurement with the charging power, and transmits the sensor signal to the reading device 120.

[0019] Therefore, even when the train 50 moves, it is preferable that the distance d in the X direction between the inner wall 10 of the tunnel and the train 50 is substantially constant. The distance d may be treated as the distance in the X direction between the sensor device 110 and the train 50. Also, it is preferable that the heights (Z-direction heights) of the plurality of sensor devices 110 are equal. Further, it is preferable that the height of the antenna of the plurality of sensor devices 110 and the height of the reading device 120 mounted on the train 50 are substantially equal, and even if there is a difference in height, it is preferable that the difference is such that it does not affect the transmission and reception of the reading signal and the sensor signal.

[0020] Note that the structure is not limited to the inner wall 10 of the tunnel, and may be a building or the like that extends along the traveling direction of the moving body. The structure fastening part is not limited to bolts, nuts, etc. provided in the fixing part for fixing a power cable or the like, and may be, for example, a member that fastens the fixing part for fixing a sleeper or the like that fixes a railway track to the ground. Also, the moving body is not limited to the train 50, and may be a vehicle, a ship, an aircraft, or the like.

[0021] <Specific configuration of the sensor device 110> Here, it will be described with reference to FIG. 2. FIG. 2 is a diagram showing an example of the specific configuration of the sensor device 110. As an example, the sensor device 110 includes an antenna 111, an RF (Radio Frequency) circuit 112, an IC (Integrated Circuit) chip 113, a capacitor 114, a MCU (Micro Controller Unit) 115, an amplifier 116, and a sensor 117. The IC chip 113 is an example of a transmission / reception unit.

[0022] The antenna 111 is an antenna that receives a reading signal and transmits a sensor signal. The antenna 111 may be an antenna capable of transmitting and receiving signals in the 920 MHz band. As such an antenna 111, for example, a dipole antenna, an inverted F-type antenna, a patch antenna, or a monopole antenna can be used.

[0023] The RF circuit 112 is a circuit that performs impedance matching between the antenna 111 and the IC chip 113. The RF circuit 112 includes capacitors, coils, etc.

[0024] IC chip 113 is a passive RFID (Radio Frequency Identifier) ​​chip. IC chip 113 has a rectifier circuit, and when a read signal is received by antenna 111 and input via RF circuit 112, it converts the AC power based on the read signal into DC power and charges capacitor 114. IC chip 113 is also connected to MCU 115 for data communication. Figure 2 shows four data communication lines between IC chip 113 and MCU 115 as an example. IC chip 113 has a built-in regulator, and when the terminal voltage VDD of capacitor 114 exceeds the threshold voltage Vth (described later), it converts the voltage VDD of the power charged in capacitor 114 into voltage Vr and supplies it to MCU 115. Voltage Vth is the terminal voltage VDD when the charge amount of capacitor 114 reaches a predetermined amount that enables the transmission of a sensor signal. The IC chip 113 has an internal memory that stores identification information representing a unique ID. When the MCU 115 operates and outputs a sensor signal to the IC chip 113, the IC chip 113 outputs a modulated wave based on the ID and the sensor signal to the RF circuit 112. The sensor signal is radiated from the antenna 111.

[0025] Capacitor 114 is inserted in series between the output terminal of the rectifier circuit of the IC chip 113 and the ground potential point (the point indicated by the inverted triangle symbol). Capacitor 114 stores power for driving the sensor device 110.

[0026] The MCU115 operates when a voltage Vr is supplied from the IC chip 113, and controls the operation of the IC chip 113, supplies power to the amplifier 116, and applies voltage to the sensor 117. Furthermore, when the MCU115 acquires the analog value of the sensor signal amplified by the amplifier 116, it converts it to a digital value and outputs it to the IC chip 113.

[0027] Amplifier 116 is connected to the bridge circuit of sensor 117 and amplifies the sensor signal output by sensor 117 and outputs it to MCU 115.

[0028] Sensor 117 has four bridge-connected strain detection elements 117A. Sensor 117 is a washer-type sensor fastened to the fixed part together with the bolt and nut described above, and has a configuration in which four strain detection elements 117A are attached to the surface of a washer which acts as a strain generating body. As an example, strain resistance elements whose resistance value changes according to the amount of strain of the strain generating body can be used as the four strain detection elements 117A. Sensor 117 outputs a sensor signal to amplifier 116 corresponding to the change in the resistance values ​​of the four strain detection elements 117A.

[0029] <Configuration of reading device 120> As shown in Figure 1, the reading device 120 includes an antenna 121 and a transmitting / receiving unit 122. Power is supplied to the reading device 120, for example, from the power supply unit (not shown) of the train 50, and it is operational while the train 50 is running (while the moving object is in motion). When the train 50 is moving in the +Y direction, all of the reading devices 120A to 120C transmit a reading signal. This is because they transmit a reading signal sequentially to each of the multiple sensor devices 110 installed on the inner wall 10 of the tunnel.

[0030] Antenna 121 can be any antenna capable of transmitting and receiving signals in the 920MHz band. Examples of such antennas 121 include an inverted F antenna, a patch antenna, or a monopole antenna.

[0031] The transmitting / receiving unit 122 is connected to the antenna 121 and transmits wireless signals via the antenna 121 and receives sensor signals from the sensor device 110. The transmitting / receiving unit 122 has a memory 122A. The transmitting / receiving unit 122 can be any wireless communication device that performs at least the transmission of wireless signals, the reception of sensor signals, and the storage of the received sensor signals in the memory 122A.

[0032] The transmitting and receiving units 122 of the reading devices 120A to 120C are configured, for example, to transmit reading signals at 920.4MHz, 916.8MHz, and 919.2MHz, respectively. Since the 920MHz band signals are divided into channels every 200kHz, the frequencies of 920.4MHz, 916.8MHz, and 919.2MHz are separated by more than 5 channels.

[0033] If the frequencies of the reading devices are the same, or if the difference between them is very small (for example, if the difference between channels is 1 or less), then multiple reading devices will need to stop outputting for a certain period of time as a result of carrier sensing. However, the frequencies used by the transmitting and receiving units 122 of the reading devices 120A to 120C are far enough apart that carrier sensing will not cause them to stop outputting to each other. Not causing them to stop outputting to each other even when carrier sensing is performed means that the three channels on which the reading devices 120A to 120C transmit reading signals are sufficiently far apart due to the distance between their frequencies, and the reading devices 120A to 120C do not need to stop transmitting reading signals to each other due to carrier sensing.

[0034] Therefore, when all of the reading devices 120A to 120C are simultaneously transmitting reading signals, none of the transmissions or receptions will be stopped by carrier sensing, ensuring reliable transmission of reading signals to the sensor device 110 and reception of sensor signals from the sensor device 110.

[0035] <Pitch p of reading devices 120A~120C> Let p be the pitch between the three reading devices 120A to 120C in the direction of movement of the train 50 (Y direction), and let d be the distance between the three reading devices 120 and the surface of the inner wall 10 of the tunnel in the direction perpendicular to the direction of movement (Y direction) (X direction) in a plan view (XY plane view).

[0036] The reading devices 120A to 120C communicate at frequencies spaced far enough apart that carrier sensing does not cause them to stop outputting from one another. However, if the distance d is close, there is a risk that they may receive reflected waves from the inner wall 10. Such reflected waves may interfere with the reception of the sensor signals that should be received. For this reason, a certain pitch p is required between the reading devices 120A to 120C, and this pitch p has a lower limit.

[0037] Furthermore, in order to efficiently read multiple sensor devices 110, the reading system 100 uses a reading device 120 mounted on the train 50 to read sensor signals while the train 50 is in motion. Since the train 50 travels in the +Y direction, one reading device 120 may not be able to sufficiently charge the capacitors 114 of the sensor devices 110. For this reason, the reading system 100 includes three reading devices 120A to 120C, and charges the capacitors 114 sequentially in the order of reading devices 120A to 120C while the train 50 is moving.

[0038] Capacitor 114 can be charged with the power of the reading signal, but unlike a secondary battery, it has a relatively large discharge rate. Therefore, when charging capacitor 114 sequentially in the order of reading devices 120A to 120C, it is desirable that the charging by each reading device 120A to 120C is interrupted as much as possible. Furthermore, it is desirable that the charging of capacitor 114 by the next reading device 120 begins while the power charged by the previous reading device 120 remains in capacitor 114. This is to charge capacitor 114 to a charge level sufficient for the sensor device 110 to operate and to ensure that the sensor signal from the sensor device 110 is reliably received by at least one of the reading devices 120A to 120C. For this reason, an upper limit is required for the pitch p between reading devices 120A to 120C.

[0039] Furthermore, there may be a period during the switching between readers 120A and 120B during which both readers 120A and 120B transmit a reading signal. The same applies to readers 120B and 120C. Charging the capacitor 114 sequentially in the order of readers 120A to 120C means that there may be overlapping periods.

[0040] For the reasons described above, in order to make it difficult for the reading devices 120A to 120C to receive reflected waves from the inner wall 10 of each other's reading signals, and to ensure that the capacitor 114 is reliably charged to a charge level that allows the sensor device 110 to operate, it is preferable that the pitch p satisfies the following equation (1A) or (1B). Note that there may be more than three reading devices 120. Also, speed V is the assumed maximum speed.

[0041]

number

[0042] Here, Dmax is the maximum communication range for each reading device 120, and V is the speed of the train 50 moving in the +Y direction. Also, Td is the discharge time from when the charge level of the capacitor 114 goes from a predetermined amount that enables the transmission of a sensor signal to zero.

[0043] <Explanation of equation (1A)> Equation (1A) represents the pitch p condition when the distance d is less than or equal to Dmax / 2, and the distance in the X direction between the reading devices 120A to 120C and the inner wall 10 of the tunnel is relatively short. In reality, the reading devices 120A to 120C are spaced apart in the Y direction, but under the most stringent conditions, we consider that when the train 50 is moving in the +Y direction, the reading signal and the reflected wave at the inner wall 10 propagate only in the X direction. In this case, for adjacent reading devices 120A and 120B, the condition that the distance d is less than or equal to Dmax / 2 means that the reflected wave of the reading signal transmitted by reading device 120A can reach reading device 120B. In reality, since the train 50 is moving in the +Y direction, such an event does not actually occur, but in order to suppress the occurrence of such an event, the lower limit of the pitch p when the distance d is less than or equal to Dmax / 2 is set to d / 2. This also applies to the relationship between adjacent reading devices 120B and 120C.

[0044] Furthermore, if the pitch p between adjacent reading devices 120A and 120B is too large, there is a risk that the capacitor 114 may discharge and its charge level may drop to zero between the time reading device 120A finishes charging the capacitor 114 and the time reading device 120B begins charging the capacitor 114.

[0045] From this perspective, the upper limit of the pitch p is set to 2 × Dmax + V × Td, taking into account the moving speed V of the train 50. Although the reading devices 120A to 120C actually transmit reading signals in the -X direction, under the most stringent conditions, we consider that the reading signals propagate in the Y direction. In this case, we consider the adjacent reading devices 120A and 120B as follows: In order for the power charged by reading device 120A to remain in the capacitor 114 between the time reading device 120A finishes charging the capacitor and the time reading device 120B begins charging the capacitor, the distance between reading devices 120A and 120B in the Y direction should satisfy the following condition: That is, when reading device 120A, sensor device 110, and reading device 120B are arranged in the Y direction in that order, the distance between reading device 120A and sensor device 110 should be Dmax, and the distance between sensor device 110 and reading device 120B should be Dmax. In other words, the distance in the Y direction between reading device 120A and reading device 120B should be 2 × Dmax.

[0046] Furthermore, in reality, the reading devices 120A and 120B are moved in the +Y direction at a speed V by the train 50. Therefore, considering the discharge time Td from when the charge level of the capacitor 114 goes from a predetermined amount that enables the transmission of a sensor signal to zero, if we add the distance V × Td that the train 50 moves during the discharge time Td to the above 2 × Dmax, the upper limit of the pitch p becomes 2 × Dmax + V × Td.

[0047] <Explanation of formula (1B)> Equation (1B) represents the pitch p condition when the distance d is longer than Dmax / 2, and the distance in the X direction between the reading devices 120A~120C and the inner wall 10 of the tunnel is relatively long.

[0048] The upper limit of the pitch p should be set to 2 × Dmax + V × Td, similar to the case where the distance d is less than or equal to Dmax / 2. This is because even if the distance d is longer than Dmax / 2, if the pitch p is too large, the charge level of the capacitor 114 will decrease significantly before the next reading device 120 can be charged.

[0049] Furthermore, the lower limit of the pitch p when the distance d is longer than Dmax / 2 can be considered as follows: When the distance d between the reading devices 120A~120C and the inner wall 10 of the tunnel is longer than Dmax / 2, even under the most severe condition, where the reading signal and reflected wave propagate only in the X direction when the train 50 is moving in the +Y direction, the reflected wave will not reach the reading devices 120A~120C.

[0050] Therefore, when the distance d is longer than Dmax / 2, the lower limit of the pitch p of the reading devices 120A to 120C is set to λ / 2, which is the typical pitch when two antennas are placed next to each other. λ is the wavelength of the reading signal in free space.

[0051] <An example of the time change in the charge level of capacitor 114> Figure 3 shows an example of the time variation of the charge level of capacitor 114. In Figure 3, the horizontal axis represents time, and the vertical axis represents the terminal voltage VDD (V) of capacitor 114. The terminal voltage VDD corresponds to the charge level of capacitor 114. Here, we will explain an example of the time variation of the terminal voltage VDD when capacitor 114 is charged sequentially using reading devices 120A to 120C arranged at a pitch p that satisfies the above-described equation (1A) or equation (1B).

[0052] Voltage Vth is the terminal voltage VDD of capacitor 114 when the charge level of capacitor 114 reaches a predetermined amount that enables the transmission of a sensor signal. In other words, voltage Vth is the lower limit of the terminal voltage VDD of capacitor 114 when the sensor device 110 has performed a measurement with sensor 117 and is in a state where it can transmit a sensor signal from antenna 111.

[0053] At time t1, the reading device 120A begins charging the capacitor 114, and the terminal voltage VDD starts to rise. The charging of the capacitor 114 by the reading device 120A continues until time t2.

[0054] After time t2, for example, the terminal voltage VDD decreases because charging of capacitor 114 by the next reading device 120B has not yet begun.

[0055] At time t3, the reading device 120B begins charging the capacitor 114, and the terminal voltage VDD starts to rise again. The reading device 120B continues charging the capacitor 114 until time t4. At time t4, the terminal voltage VDD has not reached Vth, so the sensor device 110 does not operate.

[0056] After time t4, for example, the terminal voltage VDD decreases because charging of capacitor 114 by the next reading device 120C has not yet begun.

[0057] At time t5, the reading device 120C begins charging the capacitor 114, and the terminal voltage VDD starts to rise. At time t6, the terminal voltage VDD becomes greater than or equal to Vth, so the sensor device 110 becomes operational. The reading device 120C continues charging the capacitor 114 until time t7. After time t7, charging stops, so the terminal voltage VDD decreases.

[0058] At time t8, the terminal voltage VDD falls below Vth, so the sensor device 110 stops operating. In other words, the period between time t6 and time t8 is the period during which the sensor device 110 can operate. During this period, the sensor device 110 should detect strain with sensor 117 and transmit a sensor signal. As a result, the reading device 120C can receive the sensor signal.

[0059] In the example shown in Figure 3, if charging of the capacitor 114 by the reading device 120C does not begin at time t5, the terminal voltage VDD will continue to decrease as shown by the dashed line.

[0060] As the reading devices 120A to 120C move along the train 50, the capacitors 114 of each sensor device 110 are charged sequentially. If the terminal voltage VDD of the capacitor 114 changes as shown in Figure 3, for example, the reading device 120C can receive the sensor signal.

[0061] <Control device 130> As shown in Figure 1, the control device 130 is connected to the reading devices 120A to 120C. The control device 130 is, for example, composed of a computer. The control device 130 starts transmitting reading signals simultaneously to all of the reading devices 120A to 120C, and stops transmitting reading signals to all of the reading devices 120A to 120C once readings for all of the sensor devices 110 are complete. The control device 130 also acquires the sensor signals received by the reading devices 120A to 120C.

[0062] <Experimental Results (Part 1)> Figure 4A is a characteristic diagram showing an example of experimental results (Part 1). Two reading devices 120A and 120B were placed along the direction of movement (Y direction) of the moving object, and the reading devices 120A and 120B were passed in front of a single sensor device 110 in that order. The experiment confirmed how the terminal voltage VDD of the capacitor 114 of the sensor device 110 and the voltage Vr output by the IC chip 113 changed. Both reading devices 120A or 120B were kept transmitting reading signals from the start to the end of the measurement.

[0063] The reading devices 120A and 120B communicate at 920.4MHz and 916.8MHz, respectively. The pitch p in the direction of movement (Y direction) of the reading devices 120A and 120B was set to 1.6m, and the distance in the X direction between the sensor device 110 and the train 50 was set to a predetermined distance. In addition, the height of the reading devices 120A and 120B and the sensor device 110 were made the same.

[0064] Figure 4A shows the period during which it was confirmed that the capacitor 114 was charged in each of the reading devices 120A and 120B, indicated by double arrows.

[0065] When the mobile body equipped with reading devices 120A and 120B was moved in the +Y direction, the terminal voltage VDD of the capacitor 114 was measured with an oscilloscope. As shown in Figure 4A, the terminal voltage VDD of the capacitor 114 first increased as it was charged by the reading device 120A. When the charging switched from the reading device 120A to the reading device 120B, the terminal voltage VDD decreased slightly, but the decrease was only about 30%, and when the charging of the reading device 120B began, the terminal voltage VDD increased again.

[0066] Furthermore, the voltage Vr output by the IC chip 113 initially reached a predetermined value through charging by the reader 120A, and then only showed a slight decrease during the transition from charging the reader 120A to charging the reader 120B. This confirmed that the MCU 115 was operational for almost the entire period from immediately after the start of charging the reader 120A to the end of charging the reader 120B. The MCU 115 is operational when the sensor device 110 is able to transmit the sensor signal obtained from the sensor 117.

[0067] As described above, the experimental results confirmed that by moving the mobile body equipped with reading devices 120A and 120B in the +Y direction, the capacitors 114 of the sensor device 110 can be charged sequentially, and the sensor device 110 can be made capable of transmitting sensor signals.

[0068] Furthermore, Figure 4B shows the results of obtaining a log of the communication status of the readers 120A and 120B when the capacitor 114 was being charged, as shown in Figure 4A. Figure 4B is a diagram showing an example of the communication status log when the experimental results (part 1) were obtained. Figure 4B shows the period during which the capacitor was being charged by the readers 120A and 120B, indicated by double arrows in Figure 4A.

[0069] In Figure 4B, the horizontal axis represents time, and the vertical axis represents the communication status level of the reading devices 120A and 120B. The communication status on the vertical axis is shown in levels 0 to 3. Level 3 indicates that the communication status of the reading devices 120A and 120B is good, and they can receive sensor signals from the sensor device 110. Level 2 indicates that the communication status of the reading devices 120A and 120B is not good, and it is somewhat difficult to receive sensor signals from the sensor device 110. Level 1 indicates that the communication status of the reading devices 120A and 120B is poor, and it is difficult to receive sensor signals from the sensor device 110. Level 0 indicates that the reading devices 120A and 120B are unable to communicate with the sensor device 110. Note that no marker is shown at level 0.

[0070] As shown in Figure 4B, it was confirmed that a Level 3 communication state can be obtained during the period when the readers 120A and 120B, indicated by the double-headed arrows, are charging. Furthermore, it was confirmed that during the period when charging of reader 120A ends and the charging switches to reader 120B (the period between the two double-headed arrows), the communication state level of reader 120A becomes level 0, and the communication state of reader 120B transitions from Level 2 to Level 3.

[0071] From the communication status log shown in Figure 4B, it was confirmed that by moving the mobile body equipped with the reading devices 120A and 120B in the +Y direction, the capacitors 114 of the sensor device 110 could be charged sequentially, and the sensor device 110 could be made capable of transmitting sensor signals.

[0072] <Experimental Results (Part 2)> Figures 5A to 5C are characteristic diagrams showing an example of experimental results (Part 2). Two reading devices 120A and 120B were arranged along the direction of movement (Y direction) of the moving object, and the reading devices 120A and 120B were passed in front of a single sensor device 110 in that order. The experiment confirmed whether reading device 120A or 120B received a sensor signal from sensor device 110. In other words, the communication status between reading device 120A or 120B and sensor device 110 was confirmed. Both reading devices 120A or 120B were kept transmitting reading signals from the start to the end of the measurement.

[0073] The reading devices 120A and 120B communicate at 920.4MHz and 916.8MHz, respectively. The pitch p in the direction of movement (Y direction) of the reading devices 120A and 120B was set to 1.6m, and the distance in the X direction between the sensor device 110 and the moving object was set to 1m. In addition, the height of the reading devices 120A and 120B was made the same as that of the sensor device 110. Furthermore, the reading device 120B was tilted backward so that, in a plan view, it faces 20 degrees counterclockwise with respect to the -X direction relative to the direction of movement (Y direction) of the moving object.

[0074] In the experiment, the moving speed of the moving object as it passed in front of the sensor device 110 (the +X direction side of the sensor device 110 in Figure 1) was set to 20 km / h, 30 km / h, 40 km / h, 50 km / h, and 60 km / h, and three measurements were taken at each moving speed.

[0075] In Figures 5A to 5C, the horizontal axis represents the travel speed (km / h), and the vertical axis represents the communication status. The communication status of readers 120A and 120B is indicated by levels 0 to 3, similar to Figure 4B. The meanings of levels 0 to 3 are the same as in Figure 4B. In Figures 5A to 5C, a marker is also shown for level 0.

[0076] Figure 5A shows the communication status of reader 120A when only reader 120A transmits a read signal. In the experiment to obtain the results shown in Figure 5A, reader 120B did not transmit a read signal.

[0077] A communication status of reading device 120A at level 3 indicates that reading device 120A, which is the first to pass in front of sensor device 110, has sufficiently charged capacitor 114 and received the sensor signal. A communication status of reading device 120A at level 2 or lower indicates that reading device 120A, which is the first to pass in front of sensor device 110, may not be able to sufficiently charge capacitor 114 and therefore may not be able to receive the sensor signal.

[0078] As shown in Figure 5A, the reader 120A achieved a Level 3 communication status all three times at 20 km / h and 30 km / h. At 40 km / h, the reader 120A achieved a Level 2.5 communication status once and a Level 2 communication status twice. At 50 km / h, the reader 120A achieved a Level 2 communication status once and a Level 1 communication status twice. At 60 km / h, the reader 120A achieved a Level 0 communication status all three times.

[0079] In other words, it was found that the reading device 120A alone can operate the sensor device 110 when the travel speed is 20 km / h and 30 km / h, but it cannot operate the sensor device 110 alone when the travel speed is 40 km / h or higher.

[0080] Figure 5B shows the communication status of reader 120A when readers 120A and 120B sequentially transmit reading signals. The meaning of communication status levels 0 to 3 is the same as in Figure 5A.

[0081] As shown in Figure 5B, the reader 120A achieved a Level 3 communication status all three times at 20 km / h. At 30 km / h, the reader 120A achieved a Level 2.5 communication status once and a Level 0 communication status twice. At 40 km / h, the reader 120A achieved a Level 2 communication status once and a Level 0 communication status twice. At 50 km / h and 60 km / h, the reader 120A achieved a Level 0 communication status all three times.

[0082] In other words, it was found that if the travel speed is 20 km / h, the reader 120A can operate the sensor device 110 by itself when the reader 120A and 120B sequentially transmit reading signals, but at speeds of 30 km / h or higher, the reader 120A cannot operate the sensor device 110 by itself.

[0083] Figure 5C shows the communication status of reader 120B when readers 120A and 120B sequentially transmit reading signals. The meanings of communication status levels 0 to 3 are the same as in Figures 5A and 5B.

[0084] As shown in Figure 5C, the reader 120A maintained a Level 3 communication status all three times at speeds between 20 km / h and 50 km / h. At 60 km / h, the reader 120A maintained a Level 2.5 status all three times.

[0085] In other words, it was found that if the travel speed is 50 km / h or less, the sensor device 110 can be activated and the reader device 120B can receive the sensor signal when the reader devices 120A and 120B sequentially transmit reading signals. At speeds of 60 km / h or more, the sensor device 110 could not be activated.

[0086] From the above experiments, it was confirmed that by appropriately setting the communication frequency, pitch p, and movement speed, the reading devices 120A and 120B can sequentially transmit reading signals to the sensor device 110 while moving as mobile units, and as a result, the capacitor 114 of the sensor device 110 can be sufficiently charged, making it possible to receive sensor signals.

[0087] <Effects> The reading system 100 includes a sensor device 110 installed on a structure (10) having a transmitting / receiving unit (IC 113) and a capacitor capable of storing power to drive the transmitting / receiving unit, which receives a wireless signal that can charge the capacitor at the transmitting / receiving unit and transmits a sensor signal, and a plurality of reading devices 120 that transmit a wireless signal that can charge the capacitor 114 and receive a sensor signal from the sensor device 110, which are mounted on a mobile body that moves along the structure (10), and each reading device 120 has an antenna 121 and a transmitting / receiving unit 122 that transmits a wireless signal and receives a sensor signal via the antenna 121, and the plurality of transmitting / receiving units 122 of the plurality of reading devices 120 transmit a wireless signal and receive a sensor signal at frequencies that are spaced far enough apart that their output does not stop even when they perform carrier sensing on each other. As a result, the capacitor 114 of the sensor device 110 can be charged sequentially by the plurality of reading devices 120, and the sensor device 110 can be operated to receive a sensor signal. Multiple reading devices can transmit reading signals sequentially and efficiently without being interrupted by carrier sensing.

[0088] Therefore, by using multiple reading devices 120, a reading system 100 capable of reliably receiving sensor signals can be provided.

[0089] Furthermore, the multiple reading devices 120 may be arranged along the direction of movement of the moving body. By arranging the multiple reading devices 120 along the direction of movement, the reading devices 120 can efficiently transmit reading signals sequentially to the sensor device 110, thereby enabling more reliable reception of the sensor signal.

[0090] Furthermore, when the charge level of the capacitor 114 becomes sufficient to transmit a sensor signal, the sensor device 110 may transmit its own identification information and the sensor signal. Since the reading device 120 can receive the identification information along with the sensor signal, it can easily identify which sensor device 110 transmitted the sensor signal.

[0091] Furthermore, the sensor signal represents the fastening force of the structural fastening part, and when the reading device 120 receives the sensor signal, it may store the sensor signal in the memory 122A. Even without an inspector directly examining the fastening state of the structural fastening part, the fastening state of the structural fastening part can be measured remotely via wireless communication while moving in a mobile device.

[0092] Furthermore, if p is the pitch of the moving bodies of the multiple reading devices 120 in the direction of movement, d is the distance between the multiple reading devices 120 and the surface of the structure (10) in a direction perpendicular to the direction of movement in a plan view, Dmax is the maximum communication distance of the multiple reading devices 120, V is the speed of movement of the moving bodies in the direction of movement, and Td is the discharge time from when the charge amount of the capacitor 114 goes from a predetermined amount that enables the transmission of a sensor signal to zero, then the pitch p may satisfy the following equation (1A) or (1B).

[0093]

number

[0094] By arranging multiple reading devices 120 such that the pitch p satisfies equation (1A) or (1B), the capacitor 114 of the sensor device 110 can be charged sequentially according to the moving speed of the moving object, thereby enabling the sensor device 110 to operate more reliably and receive sensor signals.

[0095] While exemplary embodiments of reading systems of this disclosure have been described above, this disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0096] The following additional information is disclosed regarding the embodiments described above. (Note 1) A sensor device installed in a structure, having a transmitting / receiving unit and a capacitor capable of storing power to drive the transmitting / receiving unit, wherein the transmitting / receiving unit receives a wireless signal capable of charging the capacitor and transmits a sensor signal, A plurality of reading devices that transmit a wireless signal capable of charging the capacitor and receive a sensor signal from the sensor device, wherein the plurality of reading devices are mounted on a mobile body that moves along the structure. Includes, Each reading device, Antenna and, A transmitting and receiving unit that receives the wireless signal and the sensor signal via the antenna. It has, A reading system in which the multiple transmitting and receiving units of the multiple reading devices transmit the wireless signal and receive the sensor signal at frequencies that are spaced far enough apart that their output does not stop even when they perform carrier sensing on each other. (Note 2) The reading system described in Appendix 1, wherein the plurality of reading devices are arranged along the direction of movement of the moving body. (Note 3) The reading system according to Appendix 1 or 2, wherein the sensor device transmits its own identification information and the sensor signal when the charge level of the capacitor becomes sufficient to transmit the sensor signal. (Note 4) The aforementioned sensor signal is a signal representing the fastening force of the structural fastening part. The reading device, upon receiving the sensor signal, stores the sensor signal in memory, as described in any one of the appendices 1 to 3. (Note 5) If p is the pitch of the plurality of reading devices in the direction of movement of the moving body, d is the distance between the plurality of reading devices and the surface of the structure in a direction perpendicular to the direction of movement in a plan view, Dmax is the maximum communication distance of the plurality of reading devices, V is the speed of movement of the moving body in the direction of movement, and Td is the discharge time from when the charge amount of the capacitor changes from a predetermined amount that enables the transmission of the sensor signal to zero, then The pitch p is a reading system according to any one of the items 1 to 4 of the appendix, satisfying the following equation (1A) or (1B).

[0097]

number

[0098] 10. Inner wall of a tunnel (an example of a structure) 50 Trains (an example of a moving object) 100 reading systems 110 Sensor device 111 Antenna 112 RF circuit 113 IC chip (example of a transceiver) 114 Capacitors 115 MCU 116 Amplifier 117 Sensor 117A Strain detection element 120, 120A~120C reading device 121 Antenna 122 Transmitter / Receiver 122A Memory 130 Control device

Claims

1. A sensor device installed in a structure, having a transmitting / receiving unit and a capacitor capable of storing power to drive the transmitting / receiving unit, wherein the transmitting / receiving unit receives a wireless signal capable of charging the capacitor and transmits a sensor signal, A plurality of reading devices that transmit the wireless signal capable of charging the capacitor and receive the sensor signal from the sensor device, wherein the plurality of reading devices are mounted on a mobile body that moves along the structure. Includes, Each reading device, Antenna and, A transmitting and receiving unit that transmits the wireless signal and receives the sensor signal via the antenna. It has, A reading system in which the multiple transmitting and receiving units of the multiple reading devices transmit the wireless signal and receive the sensor signal at frequencies that are spaced far enough apart that their output does not stop even when they perform carrier sensing on each other.

2. The reading system according to claim 1, wherein the plurality of reading devices are arranged along the direction of movement of the moving body.

3. The reading system according to claim 1, wherein the sensor device transmits its own identification information and the sensor signal when the charge level of the capacitor becomes sufficient to transmit the sensor signal.

4. The aforementioned sensor signal is a signal representing the fastening force of the structural fastening part. The reading system according to claim 1, wherein the reading device, upon receiving the sensor signal, stores the sensor signal in a memory.

5. If p is the pitch of the plurality of reading devices in the direction of movement of the moving body, d is the distance between the plurality of reading devices and the surface of the structure in a direction perpendicular to the direction of movement in a plan view, Dmax is the maximum communication distance of the plurality of reading devices, V is the speed of movement of the moving body in the direction of movement, and Td is the discharge time from when the charge amount of the capacitor becomes zero, then, The reading system according to any one of claims 1 to 4, wherein the pitch p satisfies the following formula (1A) or (1B). [Math 1]

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