Structural health monitoring system, monitoring circuit, and structural health monitoring method

Abstract

To provide a structural health monitoring system with a simpler configuration and reduced installation work burden.SOLUTION: A structural health monitoring system includes a monitoring circuit fixed to the surface of a monitoring object and a determining unit that determines the health of the monitoring object based on a physical quantity detected by the monitoring circuit. The monitoring object includes a conductive base material and an insulating film fixed to the surface of the base material. The monitoring circuit includes a detector that can detect capacitance as the physical quantity and a conductive path connected in series to the detector, and at least the conductive path is fixed to the surface of the insulating film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a system for monitoring the health of a structure. [Background technology]

[0002] Structural health monitoring (SHM) refers to attaching sensors to a structure to detect physical quantities, and diagnosing and predicting damaged and deteriorated parts of the structure based on the detected physical quantities. Patent Document 1 discloses a structural damage detection device that is suitable for use in aircraft, for example.

[0003] The structural damage detection device described in Patent Document 1 consists of a capacitor formed by sandwiching a sheet-shaped insulating dielectric fixed along the surface of a structural material between sheet-shaped conductors, and a capacitor capacitance measurement circuit that detects the capacitance of the capacitor. This capacitor is formed by sandwiching a sheet-shaped insulating dielectric made of oil-impregnated paper, polyester film, barium titanate, or the like, between sheet-shaped conductors such as copper foil or aluminum foil. Patent Document 1 describes how, when damage occurs to the inspection target, the capacitor is also damaged in proportion to the damage, causing a change in the capacitance of the capacitor. Patent Document 1 states that by detecting this change in capacitance, it is possible to immediately detect the location of the damage, even during flight. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-298192 Summary of the Invention [Problem to be solved by the invention]

[0005] The structural damage detection device described in Patent Document 1 has a simple configuration consisting of a pre-made capacitor and a capacitor capacitance measurement circuit that detects the capacitance of this capacitor, allowing it to immediately detect damage even during flight. However, if the device is to be installed in multiple locations on the object to be inspected, the number of capacitors required will increase, and the installation work for the capacitors will be a heavy burden. Furthermore, there are practical issues with this method, such as the high cost and effort required to manufacture capacitors that fit the shape of the object to be inspected. In view of the above, an object of the present disclosure is to provide a structural health monitoring system that has a simpler configuration and reduces the burden of installation work. [Means for solving the problem]

[0006] The structural health monitoring system according to the present disclosure comprises: a monitoring circuit fixed to the surface of the object to be monitored; and a determiner that determines the health of the monitoring object based on the physical quantity detected in the monitoring circuit. The objects to be monitored are: The device comprises a conductive base material and an insulating film fixed to the surface of the base material. The monitoring circuit is The present invention includes a detector capable of detecting capacitance as a physical quantity, and a conductive path connected in series to the detector, At least the conductive path is fixed to the surface of the insulating film.

[0007] The monitoring circuit according to the present disclosure is fixed to the surface of the object to be monitored. The objects to be monitored are: The device comprises a conductive base material and an insulating film fixed to the surface of the base material. The monitoring circuit is A detector capable of detecting capacitance and a conductive path connected in series to the detector, At least the conductive path is fixed to the surface of the insulating film.

[0008] The structural health monitoring method according to the present disclosure determines the health of a monitored object based on capacitance detected in a monitoring circuit fixed to the monitored object. The objects to be monitored are: The device comprises a conductive base material and an insulating film fixed to the surface of the base material. The monitoring circuit is The present invention includes a detector capable of detecting capacitance as a physical quantity, and a conductive path connected in series to the detector, At least the conductive path is fixed to the surface of the insulating film. In a damaged state where damage has occurred in the base material, the capacitance of a parasitic capacitor generated by the base material, insulating film, and conductive path, which are layered in this order, is detected. [Effects of the Invention]

[0009] In the present disclosure, when damage to the base material causes a break at any point in the conductive path, a parasitic capacitor is generated by the base material, the insulating film, and the conductive path. Damage to the base material can be determined by detecting the capacitance of this parasitic capacitor. Because the present disclosure uses the base material and insulating film of the monitored object as components of the parasitic capacitor, all that is added to existing aircraft components is the conductive path and a detector, resulting in a simpler configuration and less installation work. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a configuration of a structural health monitoring system according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating a monitoring state in a structural health monitoring system. [Figure 3] 1A and 1B are diagrams illustrating the potential difference, electrostatic induction, and capacitive coupling state that occur in a detection circuit after damage in a structural health monitoring system. [Figure 4] FIG. 1 is a diagram illustrating a method for detecting a damage location in a structural health monitoring system. [Figure 5]FIG. 10 is a diagram showing a structural health monitoring system according to a first modified example. [Figure 6] FIG. 10 is a diagram showing a structural health monitoring system according to a second modified example. [Figure 7] FIG. 1 is a diagram illustrating an object to which a structural health monitoring system is applied. [Figure 8] 10A and 10B are diagrams illustrating a method for determining the presence or absence of damage to a base material by electrical resistance. DETAILED DESCRIPTION OF THE INVENTION

[0011] A preferred embodiment of a structural health monitoring system 1 according to the present disclosure will now be described. The structural health monitoring system 1 detects capacitance and determines the health of the structure by determining changes in capacitance. The determination of changes is performed by comparing the capacitance when the monitoring circuit 10 is healthy with the capacitance of a parasitic capacitor that is generated when a break occurs in the monitoring circuit 10.

[0012] [Configuration of Structural Health Monitoring System 1: See Figure 1] The structural health monitoring system 1 comprises a monitoring circuit 10 fixed to the surface of the object 100 to be monitored, an RFID reader 30 that reads the capacitance detected by the monitoring circuit 10 through wireless communication, and a mobile terminal 40 that acquires information relating to the capacitance from the RFID reader 30 and processes the information.

[0013] [Monitoring object 100; see Figure 1] The monitoring object 100 includes a conductive base material 101 and an insulating film 103 made of an electrically insulating material that covers the surface of the base material 101. The direct target of the structural health monitoring system 1 for determining the health of the base material 101 is the base material 101, but if damage, such as a crack, occurs on the surface of the base material 101, the crack in the base material 101 may also cause a crack in the insulating film 103 that covers the surface of the base material 101. The structural health monitoring system 1 utilizes the fact that the conductive base material 101 and the insulating film 103 are layered together to generate a parasitic capacitor between the monitoring circuit 10 and the monitoring object 100. The parasitic capacitor will be described in detail in the description of the monitoring circuit 10. Although the monitoring object 100 shown here is rectangular in plan view, this merely shows a portion of the structure to be monitored.

[0014] The base material 101 is made of a metal material such as iron, iron alloy, aluminum, or aluminum alloy, and is electrically conductive. The insulating film 103 includes both a form not derived from the base material 101 and a form derived from the base material 101. A form not derived from the base material 101 typically includes a coating film formed by applying a paint made of a resin material. Another form derived from the base material 101 is anodized aluminum if the base material 101 is aluminum. Anodized aluminum refers to a coating made of aluminum oxide that is artificially formed on the surface of aluminum by, for example, electrolytically treating aluminum with an anode. The insulating film 103 adheres to the surface of the base material 101 and does not easily peel off from the base material 101. The thicknesses of the base material 101 and the insulating film 103 are arbitrary, but the insulating film 103 is usually thinner than 101.

[0015] [Monitoring circuit 10: See Figure 1] The monitoring circuit 10 includes a detector 11 capable of detecting capacitance and a conductive path 15 connected to the detector 11. The detector 11 and the conductive path 15 are fixed at a predetermined position on the monitoring object 100 by, for example, attaching them to the surface of the insulating film 103.

[0016] <Detector 11> An LCR meter is used as an example of the detector 11. The LCR meter is a measuring instrument that applies an AC voltage of a certain frequency to the object to be measured, measures the AC current and phase difference, and calculates the capacitance from the impedance and phase difference. The LCR meter can calculate inductance (L) and resistance (R) in addition to capacitance (C), but the structural health monitoring system 1 only calculates capacitance.

[0017] Detector 11 has a pair of lead wires 13A and 13B connected to terminals 12A and 12B, respectively. Both ends of conductive path 15 are connected between lead wires 13A and 13B, and detector 11 and conductive path 15 form a series circuit. By applying an AC voltage of a certain frequency to detector 11 as an LCR meter and conductive path 15, the capacitance between conductive path 15 and monitoring object 100 can be determined.

[0018] The detector 11 preferably has a wireless function. Specifically, the detector 11 is included in an RFID (Radio Frequency Identification) system, that is, a system that uses radio waves to contactlessly exchange tag data. The capacitance measured by the detector 11 is read by an RFID reader 30 via wireless communication. The detector 11 is provided as an RFID tag. This RFID tag preferably operates using wireless power from the RFID reader 30, for example. This eliminates the need to provide a power source for operating the detector 11 near the monitoring target 100.

[0019] <Conductive path 15> The conductive path 15 is composed of a linear film or wire made of a conductive material. Any means can be used to fix the conductive path 15 to the insulating film 103, and may be, for example, by attaching a metal tape to a predetermined position on the insulating film 103, or by applying and curing a conductive paint containing a conductive filler such as metal powder to a predetermined position on the insulating film 103. In the structural health monitoring system 1, it is assumed that the conductive path 15 breaks when damage occurs to the monitored object 100. When the conductive path 15 breaks, a parasitic capacitor is generated due to the presence of the insulating film 103 between the conductive path 15 and the base material 101, both of which are conductive. In this manner, in this embodiment, one of the conductors and the dielectric for generating the parasitic capacitor is configured by the base material 101 and the insulating film 103 of the monitored object 100.

[0020] [RFID reader 30: see Figure 1] The RFID reader 30 acquires information about the capacitance detected by the detector 11 of the monitoring circuit 10 from the detector 11. The RFID reader 30 transfers the acquired capacitance to the mobile terminal 40. A portable, so-called handy RFID reader is used as the RFID reader 30. An operator who performs structural health monitoring of the monitoring object 100 carries the RFID reader 30 along with the mobile terminal 40 to perform structural health monitoring of the monitoring object 100.

[0021] The RFID reader 30 may have other functions, such as an RFID writer function, in which case the detector 11 is energized by radio waves transmitted by radio waves, thereby detecting capacitance. The means for wirelessly communicating with the detector 11 is not limited to RFID tags. Examples include wireless LAN, Wi-Fi (registered trademark), Bluetooth (registered trademark), etc. The means for communicating with the detector 11 is not limited to wireless communication, and may be wired communication means such as electric wires or optical fibers.

[0022] [Mobile terminal 40: See Figure 1] The mobile terminal 40 processes information about capacitance obtained from the RFID reader 30. The mobile terminal 40 refers to a small, lightweight, and easily portable information device, such as a laptop computer, a smartphone, or a tablet terminal. The processing of information related to capacitance by the mobile terminal 40 includes evaluation of the information. For example, by comparing an actual capacitance value provided as a numerical value with a reference capacitance value, if the actual capacitance value exceeds the reference value, it can be determined that a break has occurred in the conductive path 15 and that the monitored object 100 is damaged. The processing of the information by the mobile terminal 40 also includes displaying the determination result on a display. Furthermore, the processing of the information by the mobile terminal 40 can store the obtained actual capacitance value and determination result. Although the RFID reader 30 and the mobile terminal 40 are shown as being independent, in the present disclosure, a device having the functions of both the RFID reader 30 and the mobile terminal 40 may also be used.

[0023] [Differences between healthy and damaged circuits: see Figure 2] The difference in capacitance between when the monitoring object 100 is healthy and when it is damaged will be explained with reference to Figure 2. If the monitoring object 100 is healthy, the conductive path 15 is also healthy and not broken. If the monitoring object 100 is damaged, the portion of the conductive path 15 corresponding to the damage will be broken. In other words, if the monitoring object 100 is healthy, this means that the conductive path 15 is also healthy, and if the monitoring object 100 is damaged, this means that the conductive path 15 will also be damaged. An AC voltage of a constant frequency is applied to the conductive path 15 from the detector 11.

[0024] <Healthy state: See Figure 2 G> When conductive path 15 is healthy and lead wire 13A, conductive path 15B, and lead wire 13B are conductive, no potential difference occurs between conductive path 15 and its surroundings, or even if a potential difference occurs, it is very small, and therefore no electrostatic induction occurs in base material 101. Therefore, no capacitance occurs between conductive path 15, insulating film 103, and base material 101, or even if a capacitance occurs, it is very small. In this case, the capacitance EC detected by detector 11 is 0 or EC≒0. Mobile terminal 40, which acquires the capacitance measurement results via RFID reader 30, can display a message such as "Monitoring object 100 is healthy" on display 41. Note that an equivalent electrical circuit ECC is shown in Figure 2.

[0025] <Damage status: See Figure 2 NG> Suppose that a break occurs at any location in the conductive path 15. The location of the break is indicated by the symbol R, and the electrical circuit is divided into two electrically independent parts at the break R. One part is the first path 15-1, and the other is the second path 15-2. In the example of FIG. 2, the first path 15-1 is longer than the second path 15-2 depending on the location of the break R. When the circuit is divided into two parts, the lengths of the first path 15-1 and the second path 15-2 are determined by the position of the break R.

[0026] A voltage is applied to both ends E1 and E2 of the broken conductive path 15. This generates a potential difference between end E1 and end E2. This potential difference causes electrostatic induction on the surface of the base material 101 via the insulating film 103, resulting in capacitive coupling. Therefore, in the thickness direction T of the first path 15-1 region, a parasitic capacitor C1 is generated due to the presence of the insulating film 103 between the first path 15-1 and the base material 101. Furthermore, in the thickness direction T of the second path 15-2 region, a parasitic capacitor C2 is generated due to the presence of the insulating film 103 between the second path 15-2 and the base material 101. Electrostatic capacitances EC1 and EC2 are generated in the parasitic capacitors C1 and C2, respectively.

[0027] [Damage state potential difference, electrostatic induction, and capacitive coupling state: see Figure 3] The potential difference, electrostatic induction and capacitive coupling conditions in the damaged state are explained. In the following description, it is assumed that a break R occurs in the conductive path 15 at the position shown in the plan view of Fig. 3, dividing the conductive path 15 into two, a first path 15-1 and a second path 15-2. In this example, the lengths of the first path 15-1 and the second path 15-2 are approximately equal. As shown in the plan view of FIG. 3 and the cross-sectional view (Section B-B) of FIG. 3, assume that the portion of first path 15-1 is negatively charged and the portion of second path 15-2 is positively charged. Then, the portion of base material 101 facing first path 15-1 across insulating film 103 becomes positively charged due to electrostatic induction, and a parasitic capacitor C1 is generated by first path 15-1, insulating film 103, and base material 101. Furthermore, the portion of base material 101 facing second path 15-2 across insulating film 103 becomes negatively charged due to electrostatic induction, and a parasitic capacitor C2 is generated by second path 15-2, insulating film 103, and base material 101. This configuration is shown in the circuit diagram below Section B-B of FIG. 3 as an equivalent electrical circuit. As shown in this circuit diagram, the parasitic capacitors C1 and C2 are capacitively coupled, causing a charge transfer Qm due to polarization from the parasitic capacitor C1 side to the parasitic capacitor C2 side, and an apparent current Ia flows in the opposite direction.

[0028] [Estimation of fracture location: See Figure 4] The structural health monitoring system 1 can estimate the position of a break R that occurs in the conductive path 15. This will be described with reference to Fig. 4. The mobile terminal 40 described above can estimate this position. Now, consider conductive paths 15 with different positions of fracture R. Case 1 in Fig. 4 shows an example in which the first path 15-1 is longer than the second path 15-2, and Case 2 in Fig. 4 shows an example in which the lengths of the first path 15-1 and the second path 15-2 are approximately equal.

[0029] In Case 1, the capacitance of the parasitic capacitor C11 is EC11, and the capacitance of the parasitic capacitor C21 is EC21. The capacitances EC11 and EC21 are determined depending on the length of the respective conductive paths of the first path 15-1 and the second path 15-2, and therefore the capacitances EC11 and EC21 have the following relationship: Case 1 (unit: pF): Capacitance EC11 > Capacitance EC21 Combined capacitance 1 = (EC11 * EC21) / (EC11 + EC21)

[0030] In Case 2, the capacitance of parasitic capacitor C12 is EC12, and the capacitance of parasitic capacitor C22 is EC22. The capacitances EC12 and EC22 are also determined depending on the length of the respective conductive paths of first path 15-1 and second path 15-2, so the capacitances EC12 and EC22 have the following relationship: Case 2 (unit: pF): Capacitance EC12 ≒ Capacitance EC22 Combined capacitance 2 = (EC12 * EC22) / (EC12 + EC22)

[0031] The relationship between these two capacitances is Composite capacitance 1 < Composite capacitance 2, which indicates that the break position is at a position corresponding to the composite capacitance. This means that the composite capacitance can be used to estimate the break position. The above example assumes that the length of the detection circuit and the dielectric constant of the insulating film are obtained in advance at the time of installation, but the location of the break R can be roughly estimated from the detected capacitance.

[0032] [Effects of monitoring circuit 10] The effects achieved by the monitoring circuit 10 described above will now be described. The determination is made based on the capacitance that detects whether or not there is a break in the conductive path 15. That is, when the conductive path 15 is healthy and no break occurs, there is no capacitance around the conductive path 15, or even if there is, it is very small, based on this as a criterion, and it can be determined that no damage such as a crack has occurred in the monitored object 100 in which the conductive path 15 is provided. Also, by detecting a combined capacitance formed by connecting, in series, for example, the capacitance EC1n corresponding to the first path 15-1 and the capacitance EC2n corresponding to the second path 15-2 after the break, and comparing this with the capacitance in a healthy state, which is essentially 0 (zero), it can be determined with high accuracy that damage has occurred in the monitored object 100.

[0033] In particular, unlike a case where a capacitor (pre-fabricated capacitor) is prepared in advance for the conductive path 15, the monitoring circuit 10 detects the capacitance of a parasitic capacitor that is generated when the conductive path 15 is broken, and can determine that a break has occurred in the monitoring object 100. Therefore, the monitoring circuit 10 uses the base material 101 and insulating film 103 that constitute the monitoring object 100 as elements of the parasitic capacitor, and can generate a parasitic capacitor that detects capacitance simply by adding the conductive path 15. As a result, the monitoring circuit 10 can minimize the elements that need to be added to generate the parasitic capacitor.

[0034] Furthermore, the monitoring circuit 10 can detect a capacitance that is significantly higher than 0 (zero), regardless of the position of the break in the conductive path 15, while the capacitance in a healthy state is substantially 0 (zero), and therefore can determine a break with high accuracy. In contrast, when a prefabricated capacitor (off-the-shelf capacitor) is prepared, the change in capacitance due to damage may be so small that the damage may not be recognized.

[0035] In addition, based on the amount of capacitances ECn1, ECn2, … of a plurality of conductive paths after breakage, it is possible to estimate the position in the conductive path 15 where the break R has occurred, that is, the position in the monitoring object 100 where the break R has occurred. For example, by detecting the electrical resistance value in the conductive path, it is possible to determine the presence or absence of breakage in the conductive path, but it is difficult to estimate the position of the break. This is because the method of detecting the electrical resistance value only determines the presence or absence of conduction in the conductive path.

[0036] Although the preferred embodiments in the present disclosure have been described, it is possible to select and choose the configurations given in the embodiments or to appropriately change them to other configurations. [Attachment of buffer film: refer to FIG. 5] For example, as shown in FIG. 5, conductive buffer films 17A and 17B can be connected to the basic monitoring circuit 10. The buffer films 17A and 17B are set to have a larger area than the conductive path 15 according to the capacitance measurement range and resolution of the detector 11. By providing the buffer films 17A and 17B, it becomes possible to control the capacitance generated in the circuit when damage occurs within a desired range as compared to the case where only the conductive path 15 is present.

[0037] Assume that a break R as shown in FIG. 5 has occurred in the conductive path 15. Then, in addition to the portion corresponding to the first path 15-1, capacitance also occurs in the buffer film 17A, so the capacitance increases as compared to only the first path 15-1. If the capacitance of the portion corresponding to the first path 15-1 is EC11 and the capacitance corresponding to the buffer film 17A is C17A, a total capacitance of EC11 + C17A = C1s can be detected. Here, since the relationship EC11 << EC17A holds, EC11 << C1s holds. The same applies to the second path 15-2. As described above, by connecting the buffer films 17A and 17B, a large capacitance can be detected in the monitoring circuit 10. Therefore, even if a detector 11 with a low detection limit resolution for capacitance is used, providing the buffer films 17A and 17B makes it possible to reliably detect damage to the monitoring object 100. In other words, by providing the buffer films 17A and 17B, the range of capacitance to be detected when damage occurs can be adjusted.

[0038] The buffer films 17A and 17B can be made of the same or different conductive material as that constituting the conductive path 15. Furthermore, the buffer films 17A and 17B are not limited to being connected to the illustrated leads 13A and 13B, but may be connected to any position on the conductive path 15. The areas of the buffer films 17A and 17B may be the same or different. Furthermore, the number of buffer films provided is not limited to two, but may be one, three, or more. The buffer films 17A and 17B can be provided when the monitoring circuit 10 including the conductive path 15 is installed on the monitoring object 100, thereby minimizing additional costs.

[0039] [Adding a capacitor (pre-made capacitor): See Figure 6] Instead of providing buffer films 17A and 17B, capacitors C11, C12, C13, etc. can be intentionally connected to the basic monitoring circuit 10, as shown in FIG. 6. These capacitors C11, C12, C13, etc. are referred to as off-the-shelf capacitors in this disclosure because they are originally configured as capacitors. Connecting off-the-shelf capacitors C11, C12, C13, etc. to the monitoring circuit 10 provides the same effect as connecting buffer films 17A and 17B. In addition, since the capacitances of off-the-shelf capacitors C15, C16, C17, etc. are known, damage to the monitoring object 100 can be determined with higher accuracy than when buffer films 17A and 17B are connected. Note that off-the-shelf capacitors C15, C16, C17, etc. may be provided in addition to buffer films 17A and 17B.

[0040] The number of pre-made capacitors C15, C16, C17, etc. that can be connected to the monitoring circuit 10 is arbitrary, and one or more pre-made capacitors can be connected to the monitoring circuit 10. Furthermore, when multiple pre-made capacitors C15, C16, C17, etc. are connected, the capacitances of the respective capacitors can be the same or different.

[0041] [Applicable target of Structural Health Monitoring System 1: See Figure 7] The structural health monitoring system 1 can be applied to any object, but as an example, we will use an aircraft 110. Note that the structural health monitoring system 1 can also be applied to moving objects other than the aircraft 110, such as flying objects and rockets, or to fixed objects such as bridges. As an example, a monitoring circuit 10 is provided for each of a plurality of components of the aircraft 110's airframe, such as an aileron 111, an elevator 113, and a rudder 115. Furthermore, a plurality of monitoring circuits 10 may be provided for each component. The components of the aircraft 110 are monitoring targets 100, each of which includes a base material 101 and an insulating film 103, and a monitoring circuit 10 is fixed to this insulating film 103. An identification code (ID) is assigned to each of the plurality of monitoring circuits 10, particularly to the detectors 11, and the detected capacitance is linked to this ID and read by the RFID reader 30.

[0042] Each time the aircraft is parked for inspection, the structural health monitoring system 1 is used to determine whether or not there is any damage to the aircraft 110. Inspectors carry at least the RFID reader 30 out of the RFID reader 30 and the mobile terminal 40, and rotate around to inspect objects such as the aileron 111. The mobile terminal 40 may be carried by an inspector other than the inspector who carries the RFID reader 30 and performs the inspection, and the mobile terminal 40 can also be used to view the determination results.

[0043] For example, suppose that n monitoring circuits 10 are provided at predetermined intervals on an aileron 111. Each monitoring circuit 10 is assigned an ID, such as 10-1, 10-2, or 10-n, in advance. Each monitoring circuit 10 has a predetermined communication range with an RFID reader 30. When the RFID reader 30 reaches the communication range of the monitoring circuit 10 with ID 10-1, it reads the actual measured value of the capacitance detected by the detector 11 of circuit 10-1. Next, when the RFID reader 30 reaches the communication range of the monitoring circuit 10 with ID 10-2, the communication partner switches from circuit 10-1 to circuit 10-2, and it reads the actual measured value of the capacitance detected by the detector 11 of circuit 10-2. For the aileron 111, when an inspector carrying an RFID reader 30 has completed detecting the capacitance up to the circuit 10-n, he or she then sequentially inspects the multiple monitoring circuits 10 belonging to, for example, the elevator 113.

[0044] [Damage determination by detecting other physical quantities: see Figure 8] In this embodiment, capacitance is used as the physical quantity to be detected. However, if damage to the base material 101 is determined due to a break in the conductive path 15, other electrical characteristics, such as electrical resistance, may be used as the physical quantity to be detected. That is, if the conductive path 15 is connected (Connected) as shown in the healthy state of FIG. 8 , the detector 11 measures a circuit resistance CR within a predetermined range (CR: 0 to *kΩ), and the conductive path 15 can be determined to be healthy. On the other hand, if a break occurs in the conductive path 15 (Disconnected) as shown in the damaged state of FIG. 8 , the circuit resistance CR is infinite (CR: ∞Ω), and the conductive path 15 can be determined to be in a broken state. However, according to the study of the present inventors, a predetermined circuit resistance CR may be measured (Connected) even when a break occurs in the conductive path 15. This has led to the discovery that damage to the base material 101 cannot be accurately determined using a method that detects the circuit resistance CR. In contrast, according to the present disclosure, which detects capacitance, if a break occurs in the conductive path 15, damage to the base material 101 can be determined with high accuracy by detecting the capacitance.

[0045] [Note] [1] A monitoring circuit (10) fixed to the surface of a monitoring object (100); a determiner (30, 40) that determines the health of the monitoring object (100) based on the physical quantity detected in the monitoring circuit; The object to be monitored (100) is The device comprises a conductive base material (101) and an insulating film (103) fixed to the surface of the base material (101), The monitoring circuit (10) The device includes a detector (11) capable of detecting capacitance as a physical quantity, and a conductive path (15) connected in series to the detector (11), At least the conductive path (15) is fixed to the surface of the insulating film (103).

[0046] [2] The decision unit (30, 40) is Based on the capacitance obtained from the detector (11), A structural health monitoring system (1) [1] that determines whether the base material (101) is in a healthy state where no damage has occurred or in a damaged state where damage has occurred to the base material (101).

[0047] [3] In a damaged state, a parasitic capacitor is generated by the base material (101), the insulating film (103), and the conductive path (15) stacked in this order. A structural health monitoring system (1) of [1] or [2], in which a detector (11) detects the capacitance of a parasitic capacitor.

[0048] [4] When the base material (101) is damaged, the conductive path (15) is broken and divided into at least two electrically independent paths, a first path (15-1) and a second path (15-2), The detector (11) Detecting one or both of a first capacitance (EC1) of a parasitic capacitor (C1) generated in the first path (15-1) and a second capacitance (EC2) of a parasitic capacitor (C2) generated in the second path (15-2); The decision unit (30, 40) A structural health monitoring system (1) according to any one of [1] to [3], which estimates the location of a break in a conductive path based on one or both of a first capacitance (EC1) and a second capacitance (EC2).

[0049] [5] The monitoring circuit (10) one or more buffer films (17A, 17B) made of a conductive material and electrically connected to the conductive path (15); A structural health monitoring system (1) according to any one of [1] to [4], wherein buffer films (17A, 17B) are fixed to the surface of an insulating film (103) of a monitoring object (100).

[0050] [6] The monitoring circuit (10) one or more pre-formed capacitors (C11, C12...) electrically connected to the conductive path (15); A structural health monitoring system (1) according to any one of [1] to [5], in which pre-formed capacitors (C11, C12, ...) are fixed to the surface of an insulating film (103) of a monitoring object (100).

[0051] [7] The monitoring circuit (10) a means for wirelessly communicating with the detector (11); Structural health monitoring system (1) [1]-[6]. [8] The monitoring circuit (10) comprises an RFID tag including a detector (11); The decision unit (30, 40) an RFID reader (30) for reading capacitance from an RFID tag; and a mobile terminal (40) that determines the soundness or damage state of the base material (101) based on the capacitance acquired from the RFID reader (30), The mobile terminal 40 displays the result of the determination. Structural health monitoring systems (1) from [1] to [7].

[0052] [9] A plurality of monitoring circuits (10) are provided at different positions of a monitoring object (100), The RFID tag provided in each of the plurality of monitoring circuits (10) is given an identification symbol, The mobile terminal (40) acquires the capacitance corresponding to the identification symbol via the RFID reader (30), and determines the healthy state or damaged state of the monitoring circuit (10) corresponding to the identification symbol based on the capacitance corresponding to the identification symbol. [8] structural health monitoring system (1).

[0053]

[10] A monitoring circuit (10) fixed to the surface of a monitoring object (100), The object to be monitored (100) is The device comprises a conductive base material (101) and an insulating film (103) fixed to the surface of the base material (101), The monitoring circuit (10) The device comprises a detector (11) capable of detecting capacitance and a conductive path (15) connected in series to the detector (11), At least the conductive path (15) is fixed to the surface of the insulating film (103).

[0054]

[11] A structural health monitoring method determines the health of a monitored object (100) based on capacitance detected in a monitoring circuit (10) fixed to the monitored object (100). The object to be monitored (100) is The device comprises a conductive base material (101) and an insulating film (103) fixed to the surface of the base material (101). The monitoring circuit (10) The device includes a detector (11) capable of detecting capacitance as a physical quantity, and a conductive path (15) connected in series to the detector (11), At least the conductive path (15) is fixed to the surface of the insulating film (103). In a damaged state where the base material (101) is damaged, the capacitance of a parasitic capacitor generated by the base material (101), the insulating film (103) and the conductive path (15), which are layered in this order, is detected. [Explanation of symbols]

[0055] 1. Structural Health Monitoring System 10 Monitoring Circuit 11 Detector 12A, 12B terminals 13A,13B Leader line 15 Conductive Path 15-1 Route 1 15-2 Route 2 17A, 17B Buffer film 30 RFID readers 40 Mobile Devices 100 Monitoring Objects 101 Base material 103 insulating film 110 Aircraft 111 aileron 113 elevator 115 Rudder C1, C2, C11, C21, C12, C22 Parasitic capacitors C15, C16, C17 ready-made capacitors

Claims

1. a monitoring circuit fixed to the object to be monitored; a determiner that determines the health of the monitoring object based on the physical quantity detected by the monitoring circuit, The monitoring object is The device comprises a conductive base material and an insulating film fixed to a surface of the base material, The monitoring circuit a detector capable of detecting capacitance as the physical quantity; and a conductive path connected in series to the detector; At least the conductive path is fixed to the surface of the insulating film. Structural health monitoring systems.

2. The determiner is Based on the capacitance obtained from the detector, determining whether the base material is in a healthy state where no damage has occurred or in a damaged state where damage has occurred in the base material; The structural health monitoring system of claim 1 .

3. In the damaged state, a parasitic capacitor is generated by the base material, the insulating film, and the conductive path, which are stacked in this order; The structural health monitoring system of claim 2 , wherein the detector detects the capacitance of the parasitic capacitor or a combined capacitance thereof.

4. When the base material is damaged, the conductive path is broken and divided into at least two paths, a first path and a second path, which are electrically independent from each other, The detector comprises: detecting one or both of a first capacitance of the parasitic capacitor generated in the first path and a second capacitance of the parasitic capacitor generated in the second path, or a combined capacitance thereof; The determiner is estimating a location of a break in the conductive path based on one or both of the first capacitance and the second capacitance, or a combined capacitance thereof; The structural health monitoring system of claim 3 .

5. The monitoring circuit one or more buffer films made of a conductive material and electrically connected to the conductive path; The buffer film is fixed to the surface of the insulating film of the monitoring object. The structural health monitoring system of claim 1 .

6. The monitoring circuit one or more pre-fabricated capacitors electrically connected to the conductive path; The pre-formed capacitor is fixed to the surface of the insulating film of the monitoring object; The structural health monitoring system of claim 1 .

7. The monitoring circuit means for wirelessly communicating with the detector; The structural health monitoring system of claim 1 .

8. The wireless communication means includes: an RFID tag including the detector; The determiner is an RFID reader that reads the capacitance from the RFID tag; a mobile terminal that determines a sound state or a damaged state of the base material based on the capacitance acquired from the RFID reader; The mobile terminal displays the result of the determination. The structural health monitoring system of claim 7.

9. a plurality of the monitoring circuits provided at different positions of the monitoring object; an identification symbol is assigned to the RFID tag provided in each of the plurality of monitoring circuits; the mobile terminal acquires the capacitance corresponding to the identification symbol via the RFID reader, and determines the healthy state or the damaged state of the monitoring circuit corresponding to the identification symbol based on the capacitance corresponding to the identification symbol; The structural health monitoring system of claim 8 .

10. A monitoring circuit fixed to the surface of an object to be monitored, The monitoring object is The device comprises a conductive base material and an insulating film fixed to a surface of the base material, The monitoring circuit A detector capable of detecting capacitance and a conductive path connected in series to the detector, At least the conductive path is fixed to the surface of the insulating film. Monitoring circuit.

11. 1. A structural health monitoring method for determining the health of a monitoring object based on capacitance detected in a monitoring circuit fixed to the monitoring object, comprising: The monitoring object is The device comprises a conductive base material and an insulating film fixed to a surface of the base material, The monitoring circuit A detector capable of detecting capacitance and a conductive path connected in series to the detector, At least the conductive path is fixed to the surface of the insulating film, A structural health monitoring method for detecting the capacitance of a parasitic capacitor generated by the base material, the insulating film, and the conductive path, which are stacked in this order, in a damaged state where damage has occurred in the base material.

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