KR100784071B1 - Sensors and systems for structural health monitoring - Google Patents

Abstract

The present invention provides a sensor 200 for monitoring the health of a structure (structures such as bridges, aviation, space, drones, oil refining / chemical facilities, ships, vehicles, high-rise buildings, etc.), the sensor 200 is a dielectric substrate ( 202); A piezoelectric device 208 for actuating and / or sensing a lamb wave; A molding layer 228 deposited on the piezoelectric device 208; A coating layer 206 deposited on the molding layer 228; And a hoop layer 204 surrounding the piezoelectric device 208 and attached to the substrate 202. The sensor 200 further includes an optical fiber coil sensor 210 attached to the dielectric substrate 202, wherein the optical fiber coil sensor 210 has a winding fiber optic cable 224 and an optical fiber cable 224 of the winding body. ) Has a coating layer 220 applied thereto. In addition, the present invention provides a diagnostic network patch including a plurality of patch sensors 602 attached to the main structure 610 and a bridge box 604 connected to the patch sensors 602.

Structure, sound condition, monitoring, sensor, optical fiber, wireless communication

Description

Sensors and systems for structural health monitoring

1A is a schematic partial ablation plan view of a patch sensor according to an embodiment of the present invention.

FIG. 1B is a schematic side cross-sectional view of the patch sensor shown in FIG. 1A.

1C is a schematic plan view of a typical piezoelectric device that may be used in the patch sensor of FIG. 1A.

1D is a schematic side cross-sectional view of the exemplary piezoelectric device of FIG. 1C.

1E is a schematic partial ablation plan view of a patch sensor according to another embodiment of the present invention.

FIG. 1F is a schematic side cross-sectional view of the patch sensor shown in FIG. 1E.

1G is a schematic cross-sectional view of a composite laminate including the patch sensor of FIG. 1E.

1H is a schematic side cross-sectional view of another embodiment of the patch sensor of FIG. 1E.

2A is a schematic partial ablation plan view of a hybrid patch sensor according to an embodiment of the present invention.

FIG. 2B is a schematic side cross-sectional view of the hybrid patch sensor shown in FIG. 2A.

Figure 2c is a schematic partial ablation plan view of a hybrid patch sensor according to another embodiment of the present invention.

FIG. 2D is a schematic side cross-sectional view of the hybrid patch sensor shown in FIG. 2C.

3A is a schematic partial ablation plan view of an optical fiber patch sensor according to an embodiment of the present invention.

3B is a schematic side cross-sectional view of the optical fiber patch sensor shown in FIG. 3A.

3C is a schematic partial ablation plan view of an optical fiber coil housed in the optical fiber patch sensor of FIG. 3A.

FIG. 3D is a schematic partial ablation plan view of another embodiment of the optical fiber coil shown in FIG. 3C.

3E and 3F are schematic partial ablation plan views of another embodiment of the optical fiber coil of FIG. 3C.

3G is a schematic side cross-sectional view of the optical fiber coil of FIG. 3E.

4A is a schematic partial ablation plan view of a diagnostic patch washer according to an embodiment of the present invention.

4B is a schematic side cross-sectional view of the diagnostic patch washer shown in FIG. 4A.

4C is a schematic diagram of an exemplary bolted structure using the diagnostic patch washer of FIG. 4A in accordance with an embodiment of the present invention.

4D is a schematic diagram of an exemplary bolted structure using the diagnostic patch washer of FIG. 4A in accordance with another embodiment of the present invention.

5A is a schematic diagram of an interrogation system having a sensor / actuator device in accordance with one embodiment of the present invention.

5B is a schematic diagram of an interrogation system having a sensor in accordance with one embodiment of the present invention.

6A is a schematic diagram of a diagnostic network patch system applied to a host structure in accordance with one embodiment of the present invention.

6B is a schematic diagram of a diagnostic network patch system having a strip network structure according to an embodiment of the present invention.

6C is a schematic diagram of a diagnostic network patch system having a pentagonal network structure in accordance with one embodiment of the present invention.

6D is a schematic perspective view of a diagnostic network patch system mounted in a rivet / bolt combined composite laminate in accordance with an embodiment of the present invention.

6E is a schematic perspective view of a diagnostic network patch system mounted in a composite laminate repaired with an adhesive patch according to another embodiment of the present invention.

Figure 6f is a schematic diagram showing an embodiment of a wireless communication system for controlling a remote diagnosis network patch system according to an embodiment of the present invention.

7A is a schematic diagram of a diagnostic network patch system having sensor assemblies in a strip network structure in accordance with one embodiment of the present invention.

7B is a schematic diagram of a diagnostic network patch system having sensor assemblies in a pentagonal network structure in accordance with another embodiment of the present invention.

8A is a schematic diagram of a sensor assembly including an optical fiber coil in series connection according to an embodiment of the present invention.

8B is a schematic diagram of a sensor assembly having an optical fiber coil in parallel connection according to another embodiment of the present invention.

9 is a curve diagram of an actuator and a sensor signal according to an embodiment of the present invention.

This application claims the benefit of US Provisional Application No. 60 / 505,120, filed September 22, 2003, entitled Sensors and Systems for Health Monitoring of Structures, which is incorporated herein by reference in its entirety. The present invention relates to diagnostic network patch systems (DNP systems) for the diagnosis of structures, in particular for the health monitoring of structures.

All structures in use (bridges, aviation, space, unmanned aerial vehicles, refineries / chemical installations, ships, vehicles, high-rises, etc.) require proper inspection and maintenance to prolong their life or to prevent accidental breakage. The integrity and integrity of the structure should be monitored. It is clear that the health monitoring of structures has become an important topic in recent years. To date, numerous inspection methods have been used, including conventional visual inspection and non-destructive methods such as ultrasound and eddy current scanning, acoustic emission and X-ray inspection to identify defects or damage to the structure. In these conventional inspection methods, it is necessary to at least temporarily remove the structure from use for inspection. Although the conventional methods are still used for the monitoring of isolated sites, they require a lot of time and money.

As sensor technology advances, new diagnostic techniques for monitoring the complete state of the structure have been significantly improved. Typically, these new diagnostic techniques utilize sensor systems consisting of suitable sensors and actuators mounted on the main structure. However, these problem solutions have several drawbacks and do not provide an effective online diagnostic method that provides a reliable sensor network system and / or precision monitoring method that can diagnose, classify and predict the condition of a structure with minimal manpower. For example, U. S. Patent No. 5,814, 729 to Wu et al. Discloses a method for detecting a change in attenuation characteristics of vibration waves in a structure to find a plate-shaped crack region in a laminated composite structure in the structure. A piezoceramic device is used as the actuator for generating the vibration wave, and an optical fiber cable having different grating locations is used as a sensor for receiving the wave signal. The drawback of this system is that it cannot accommodate multiple actuator arrays, so each actuator and sensor must be mounted separately. The defect detection is based on a change in the vibration wave traveling along the direct path between the actuator and the sensor, so this detection method is present around the boundary of the defect and / or structure existing outside the direct path. The defect cannot be detected.

Other defect detection methods can be found in US Pat. No. 5,184,516 to Blazic et al. This patent discloses an embedded conformal circuit for the health monitoring and evaluation of structures. This right angle circuit consists of a series of stacks of strain sensors, each of which measures strain changes at corresponding positions to identify defects in the right angle structure. The right angle circuit is a passive system, for example, does not have an actuator for signal issuance. A similar passive sensor network system can be found in US Pat. No. 6,399,939 to Mannur, J. et al. The patent discloses that a piezoceramic-fiber sensor system has planner fibers embedded in a composite structure. The drawback of these passive methods is the inability to monitor the delamination and damage between the sensors. In addition, these methods can detect the state of the main structure only in the local region where the embedded circuit and the piezoelectric fiber are attached.

US Pat. No. 6,370,964 to Chang et al. Discloses one method for detecting damage in a structure. This patent discloses a sensor network layer called the Stanford Multi-Actuator-Receiver Transduction (SMART) Layer. The SMART ^layer® includes a piezoceramic sensor / actuator in which a piezoceramic sensor / actuator (or simply, piezoceramic) is disposed at equal intervals, and the flexible dielectric film is bonded to the piezoceramic sensor / actuator via the piezoceramic sensor / actuator. The actuator generates acoustic waves, and the sensor receives the sound waves and converts them into electrical signals. To connect the piezoceramic to an electronic device, the plated wire is etched using conventional flexible circuit techniques and laminated between a plurality of circuit boards. As a result, a significant amount of flexible circuit board area is required to cover the plated wire area. In addition, the SMART layer ^® should be adhered to the main structure made of a laminated composite layer. Due to the internal stress caused by the high temperature cycle during the fixing process, the piezoceramic in the SMART layer ^® can cause microdestruction. In addition, the substrate of the SMART layer ^® can be easily separated from the main structure. In addition, since the SMART layer ^® is very difficult to insert or attach to the main structure having the fastening part, the plating wire is easily bent due to the compression load applied to the fastening part. Broken piezoelectric ceramics and bent wires are susceptible to electromagnetic interference noise and can cause induction of electrical signals. In heavy conditions, such as heat stress, battlefield shock and vibration the SMART Layer may not have ^® it does not strongly reliability as a tool for monitoring structural health. It is also expensive because the main structure must be dismantled when replacing a damaged and / or defective actuator / sensor.

Defect detection of other structures is disclosed in US Pat. No. 6,396,262 to Light et al. This patent discloses a magnetostrictive sensor for investigating damage to the structure, the sensor having a ferromagnetic strip and a coil disposed proximate the strip. The main drawback of this system is that internal damage between the sensor cannot be detected because it cannot be designed to accommodate the sensor array.

Therefore, it is easy to install in existing structures and / or new structures and is effective, precise and reliable, providing an effective online technique for state diagnosis, state classification and state prediction of structures with minimal human intervention. I need a system.

The object of the present invention is achieved by a diagnostic network patch (DNP) system that is attached to the composite and / or metal main structure. The DNP system can receive actuators / sensors and detect and monitor defects / damages of the main structure. Like the nervous system of the human body, the DNP system provides an internal wave-ray communication network in the main structure by transmitting acoustic stimuli (or lamb waves) between actuators / sensors.

According to an aspect of the present invention, a health monitoring apparatus for a structure includes a dielectric substrate, at least one buffer layer attached to the substrate, a piezoelectric device attached to the at least one buffer layer, a molding layer deposited on the piezoelectric device, and the molding. A coating layer deposited on the layer, and a pair of wires connected to the piezoelectric device, the piezoelectric device being configured to generate and / or receive a signal.

The optical fiber coil sensor for monitoring the health of a structure according to another aspect of the present invention includes an optical fiber cable roll body and a coating layer coated on the optical fiber cable roll body, and a predetermined tensile force is applied during the winding process of the optical fiber cable, and the coating layer is The tensile stress of the optical fiber cable roll is maintained.

According to still another aspect of the present invention, there is provided a health condition monitoring apparatus for a structure, comprising: a dielectric substrate, at least one sensor attached to the substrate, and a hoop layer surrounding the at least one sensor and attached to the substrate; A molding layer deposited on the at least one sensor; And a coating layer deposited on the molding layer.

According to another aspect of the present invention, an apparatus for monitoring a dry state of a structure includes a lower substrate, an upper substrate, at least one sensor interposed between the upper and lower substrates, and the at least one sensor, and attached to the upper and lower substrates. And a hoop layer.

A diagnostic patch washer according to another aspect of the invention is a ring shaped support element having a circumferential groove and a notch in the radial direction, attached to the support element, the groove And a pair of wires connected to the piezoelectric device, and an optical fiber coil sensor attached to the support element and housed in the groove. The optical fiber coil sensor includes an optical fiber cable roll body and a coating layer coated on the optical fiber cable roll body. A predetermined tensile force is applied during the winding process of the optical fiber cable, and the coating layer maintains the tensile stress of the optical fiber cable roll body. The diagnostic patch washer further includes an annular lid for covering the groove, and both ends of the pair of wires and the optical fiber cable pass through the notch.

Diagnostic network patch system for health status monitoring of the main structure according to another aspect of the present invention has a plurality of patches attached to the main structure in a predetermined pattern, at least one of the plurality of patches is the plurality of patches The vibration wave generated by at least one of the other may be received. The system also includes a bridge box connected to the plurality of patches. The bridge box includes an RF telemetry system for transmitting signals received from a plurality of patches via radio means to a ground control system.

The following description includes many illustrative details, but one of ordinary skill in the art will recognize that many various changes and modifications are possible within the scope of the invention. Accordingly, the following embodiments of the present invention are presented without loss of generality of the claims and without limiting the claims.

1A is a schematic partial ablation plan view of a patch sensor 100 according to an embodiment of the present invention. FIG. 1B is a schematic cross-sectional view of the patch sensor 100 taken along the A-A direction of FIG. 1A. As shown in FIGS. 1A-1B, the patch sensor 100 includes: a substrate 102 configured to be attached to a main structure; Hoop layer 104; Piezoelectric devices 108 for generating and / or receiving signals (especially Lamb waves); A buffer layer 110 for providing mechanical impedance matching while reducing thermal stress mismatch between the substrate 102 and the piezoelectric device 108; Two electric wires 118a-b connected to the piezoelectric device 108; A molding layer 120 for fixing the piezoelectric device 108 to the substrate 102; The coating layer 106 for protecting and sealing the molding layer 120 is provided. The piezoelectric device 108 includes a piezoelectric layer 116, a lower conductor 112 connected to the electric wire 118b, and an upper conductor 114 connected to the electric wire 118a. The piezoelectric device 108 may operate as an actuator (or equivalently, a signal generator) when a predetermined electrical signal is applied through the wires 118a-b. Upon application of an electrical signal, the piezoelectric layer 116 is deformed to produce a lamb wave. In addition, the piezoelectric device 108 includes a receiver for detecting a vibration signal, converting the vibration signal applied to the piezoelectric layer 116 into an electrical signal, and transmitting the electrical signal through the wires 118a-b. Can operate as

The substrate 102 may be attached to the main structure using a structural adhesive such as conventional casting agent thermosetting epoxy such as butyralthenolic, acrylic polyimide, nitriale phenolic or aramid. The substrate 102 may consist of an insulating layer against thermal and electromagnetic interference, protecting the piezoelectric device 108 attached thereto. In some cases, the dielectric substrate 102 needs to cope with a temperature of 250 ° C or higher. It is also possible to have a dielectric constant for minimizing signal transmission delay and crosstalk between the piezoelectric device 108 and the main structure, and high impedance for reducing power loss at high frequencies.

The substrate 102 may be made of various materials. Kapton ^® polyimide manufactured by DuPont (Wilmington, Delaware) is preferred for general use, and Teflon perfluoroalkoxy (PFA), poly p-xylylene (PPX), and polybenzimidazole (PBI) can be used for special purposes.

For example, PFA films can have good dielectric properties and low dielectric losses suitable for low voltages and high temperatures. PPX and PBI can provide stable dielectric strength at high temperatures.

The piezoelectric layer 116 may be made of piezoceramic, piezoelectric crystal, or piezoelectric polymer. Piezoelectric crystals, such as PZN-PT crystals manufactured by TRS Ceramics, Inc. of Pennsylvania State, are preferably employed in the design of piezoelectric device 108 due to its high strain energy density and low strain hysteresis. For small patch sensors, such as PZT ceramics manufactured by Fuji Ceramic Corporation, Tokyo, Japan, or APC International, Ltd., Mackeyville, Pennsylvania. Piezoceramic may be used for the piezoelectric layer 116. The upper and lower conductors 112 and 114 may be made of a metal such as chromium or gold, and may be attached to the piezoelectric layer 116 by a conventional sputtering process. In FIG. 1B the piezoelectric device 108 is shown having only a pair of conductors. However, it will be apparent to those skilled in the art that the piezoelectric device 108 may include a plurality of layers of conductors having various thicknesses for optimizing the performance of the piezoelectric layer 116 in the generation / detection of the signal wave. The thickness of each conductor can be determined by the thermal limits and mechanical loads applied to the particular main structure to which the patch sensor 100 is attached.

In order to sustain the temperature cycle, each layer of the piezoelectric device 108 needs to have a coefficient of thermal expansion similar to that of the other layers. In addition, the thermal expansion coefficient of the conventional polyimide including the substrate 102 is approximately 4-6 × 10 ⁻⁵ K ⁻¹ , and the thermal expansion coefficient of the conventional piezoelectric ceramic / crystal including the piezoelectric layer 116 is approximately 3. X 10 ^-6 K ^-1 . This mismatch in thermal expansion may be the maximum cause of failure of the piezoelectric device 108. If the piezoelectric device 108 is broken, the patch sensor 100 of the main structure should be replaced. As described above, the buffer layer 110 may be used to reduce the adverse effect of the mismatch in thermal expansion coefficient between the piezoelectric layer 116 and the substrate 102.

The buffer layer 110 is preferably made of a conductive polymer or metal, particularly aluminum having a thermal expansion coefficient of 2 × 10 ⁻⁵ K ⁻¹ . The buffer layer 110 may be replaced or added to one or more buffer layers made of alumina, silicon, or graphite. In one embodiment, the thickness of the aluminum buffer layer 110 is approximately equal to the thickness of the piezoelectric layer 116, which is about 0.25 mm thick, including two conductors 112 and 114, each about 0.05 mm thick. It can be done. In general, the thickness of the buffer layer 110 may be determined by the material properties and the thickness of the adjacent layer. The buffer layer 11 may provide durability and dual function for thermal load of the piezoelectric device 108. In other embodiments, the piezoelectric device 108 may stack another buffer layer on the upper conductor 114.

Another function of the buffer layer 110 is the amplification of the signal received by the substrate 102. As the lamb wave signal generated by the patch sensor 100 propagates along the main structure, the strength of the signal received by the other patch sensor 100 attached to the main structure decreases as the distance between the two patch sensors increases. do. When one RAM signal reaches the position where the patch sensor 100 is installed, the substrate 102 receives the signal. Next, the strength of the received signal may be amplified at a specific frequency depending on the material and thickness of the buffer layer 110. The piezoelectric device 108 then converts the amplified signal into an electrical signal.

Moisture, mobile ions, and poor environmental conditions may deteriorate the performance of the patch sensor 100 and reduce its lifetime, thereby allowing the use of two protective coating layers, namely, the molding layer 120 and the coating layer 106. . The molding layer 120 may be manufactured by a conventional manufacturing method using epoxy, polyimide, or silicon-polyimide. In addition, the molding layer 120 is made of low thermal expansion polyimide, and may be deposited on the piezoelectric device 108 and the substrate 102. Since the passivation of the molding layer 120 does not form a conformal hermetic seal, the coating layer 106 may be laminated on the molding layer 120 to seal the sealing layer. The coating layer 120 is made of a metal such as nickel, chromium or silver, and may be laminated by conventional techniques such as electrolysis or e-beam deposition and sputtering. In one embodiment, an epoxy film or polyimide film may be further coated on the coating layer 106 to provide a protective layer against scratching and cracking.

The hoop layer 104 may be made of a dielectric insulating material such as silicon nitride or glass, and surrounds the piezoelectric device 108 on the substrate 102 so that the conductive components of the piezoelectric device 108 are not electrically shorted. .

FIG. 1C is a schematic plan view of a piezoelectric device 130, which is a conventional type known in the art and may be substituted for the piezoelectric device 108. As shown in FIG. FIG. 1D is a schematic cross-sectional view of the piezoelectric device 130 taken along the B-B direction of FIG. 1C. As shown in FIGS. 1C-D, the piezoelectric device 130 includes a lower conductor 134; Piezoelectric layer 136; An upper conductor 132 connected to an electric wire 138b; A connecting member 142 connected to the electric wire 138a; And a conductive piece 144 for connecting the connecting member 142 to the lower conductor 134.

1E is a schematic partial ablation plan view of a patch sensor 150 according to another embodiment of the present invention. FIG. 1F is a schematic side cross-sectional view of the patch sensor 150 shown in FIG. 1E. As shown in Figure 1e-f, the patch sensor 150, the lower substrate 151; Upper substrate 152; Hoop layer 154; Piezoelectric device 156; Upper and lower buffer layers 160a-b; And two electric wires 158a-b connected to the piezoelectric device 108. The piezoelectric device 156 includes a piezoelectric layer 164; A lower conductor 166 connected to the electric wire 158b; And an upper conductor 162 connected to the electric wire 158a. The function and material of the patch sensor 150 are similar to those of the counterpart of the patch sensor 100. Each buffer layer 160a-b may include one or more lower layers, and each lower layer may be made of a polymer or a metal. The upper substrate 152 may be made of the same material as the material of the substrate 102.

The patch sensor 150 may be attached to the main structure to monitor the health of the structure. In addition, the patch sensor 150 may be inserted into the stack. 1G is a schematic cross-sectional view of a composite laminate 170 via a patch sensor 150. As shown in FIG. 1G, the main structure includes a plurality of stacks 172; And at least one patch sensor 150 fixed to the plurality of stacks 172. In one embodiment, the inside of the stack 172 may contain an adhesive material such as an epoxy resin before the curing process. During the curing process, the adhesive material from the stack 172 fills the cavity 174. In order to prevent accumulation of such an adhesive material, the hoop layer 154 may have a structure filling the cavity 174.

FIG. 1H is a schematic side cross-sectional view of another embodiment 180 of the patch sensor 150 of FIG. 1E. As shown, the patch sensor 180, the lower substrate 182, the upper substrate 184, the hoop layer 198; Piezoelectric device 190; Upper and lower buffer layers 186 and 188; And a piezoelectric layer 196. For simplicity, a pair of wires connected to the piezoelectric device 190 is not shown in FIG. 1H. The piezoelectric device 190 may include a piezoelectric layer 196; Lower conductor 194; And an upper conductor 192. The function and material of the components of the patch sensor 180 are similar to those of the counterpart of the patch sensor 150.

The hoop layer 198 may have one or more lower layers 197 of various dimensions such that the outline of the outside thereof matches the shape of the cavity 174. Filling the cavity 174 with the lower layer 197 prevents the adhesive material from accumulating during the curing process of the laminate 170.

2A is a schematic partial ablation plan view of a hybrid patch sensor 200 according to an embodiment of the present invention. FIG. 2B is a schematic cross-sectional view of the hybrid patch sensor 200 taken along the C-C direction of FIG. 2A. As shown in FIGS. 2A-B, the hybrid patch sensor 200 includes a substrate 202 configured to attach to a main structure; Hoop layer 204; Piezoelectric device 208; An optical fiber coil 210 having both ends 214a-b; Buffer layer 216; Two wires 212a-b connected to the piezoelectric device 208; Molding layer 228; And a coating layer 206. The piezoelectric device 208 includes a piezoelectric layer 222; A lower conductor 220 connected to the wire 212b; And an upper conductor 218 connected to the electric wire 212a. In other embodiments, the piezoelectric device 208 may be the same as the piezoelectric device 130 of FIG. 1C. The optical fiber coil 210, the optical fiber cable 224 of the winding; And a coating layer 226. The components of the hybrid patch sensor 200 may be similar to those of the counterpart of the patch sensor 100.

The optical fiber coil 210 may be configured as a Sagnac interferometer to receive a lamb wave signal. The elastic strain on the surface of the main structure caused by the lamb wave can be added on the existing strain of the fiber optic cable 224 caused by bending and stretching. As a result, the frequency / phase change amount in the movement of light through the optical fiber cable 224 depends on the total length of the optical fiber cable 224. In one embodiment, the optical fiber coil 210 may be used as the main sensor and the piezoelectric device 208 may be used as the auxiliary sensor in consideration of being not affected by electromagnetic interference and vibration noise.

The optical fiber coil 210 uses the Doppler effect to the frequency of the movement of light through the optical fiber cable 224 of the winding. In each of the optical fiber coils 210, the inside of the optical fiber winding is under compressive force and the outside is under tensile force. These compressive and tensile forces cause strain on the fiber optic cable 224. The vibrational displacement or strain of the main structure caused by the lamb wave is added to the strain of the fiber optic cable 224. According to the birefringence equation, the angle of reflection on the cladding surface of the fiber optic cable 224 is a function of the strain caused by the compressive and / or tensile forces. Thus, the inside and outside of each fiber winding produces a different angle of reflection than the inside and outside of the straight fiber, so that the frequency of light is dependent upon the relative flexural displacement of the lamb wave when light is transmitted through the fiber coil 210. Therefore, it is displaced from the center input frequency.

In one embodiment, the fiber coil 210 comprises 10 to 30 fiber optic cables 224 and has a minimum loop diameter 236 (di) of at least 10 mm. A gap 234 (dg) may exist between the innermost winding of the optical fiber coil 210 and the outer circumference of the piezoelectric device 208. This gap 234 depends on the minimum loop diameter 236 and the diameter 232 (dp) of the piezoelectric device 208, and the diameter 230 (df) of the optical fiber cable 224 than the diameter 232 of the piezoelectric device. Preferably about two or three times greater than).

The coating layer 226 is preferably composed of a metal or polymer material, in particular epoxy, to increase the sensitivity of the optical fiber coil 210 to the deflection displacement or strain of the lamb wave guided by the main structure. In addition, a controlled tensile force may be added to the optical fiber cable 224 to add a tensile stress during the winding process of the optical fiber cable 224. The coating layer 226 may maintain the internal stress of the optical fiber cable 224 of the winding body and allow uniform in-plane displacement with respect to the deflection displacement of the lamb wave for each optical fiber winding.

The coating layer 226 may be made of another material such as polyimide, aluminum, copper, gold or silver, and the thickness thereof may be in the range of about 30% to twice the diameter 230. The coating layer 226 formed of the polymer material may be formed in two ways. One embodiment is to install the optical fiber cable 224 of the winding body on the substrate 202, and then formed by spraying with a device such as a Biodot spray-coater, another embodiment of the winding body It is formed by immersing the optical fiber cable 224 in the molten bath of the coating material.

The coating layer 226 made of metal may be formed by a conventional metal coating method such as magnetron reaction sputtering or plasma sputtering as well as electrolysis. In particular, zinc oxide may be used as a coating material of the coating layer 226 to provide piezoelectric properties to the coating layer 226. When zinc oxide is coated on the upper and lower sides of the optical fiber cable 224 of the winding body, the optical fiber coil 210 contracts or expands radially concentrically in a radial direction corresponding to the electrical signal. In addition, a silicon oxide or tantalum oxide coating material may also be used to control the refractive index of the optical fiber cable 224 of the winding.

Silicon oxide or tantalum oxide can be deposited using direct / indirect ion beam deposition or electron beam vapor deposition. It is also known that the coating layer 226 can be formed on the optical fiber cable 224 using other methods without departing from the invention.

The piezoelectric device 208 and the optical fiber coil 210 may be attached to the substrate 202 using a physically solidified adhesive instead of the usual polymer. The physical coagulation adhesives include, but are not limited to, butyl acrylate-ethyl acrylate copolymer, styrene-butadiene-isoprene terpolymer, polyurethane alkyd resin, and the like. The adhesion properties of these materials can be kept constant during and after the coating process due to the lack of crosslinking of the polymer structure. In addition, these adhesives may be most suitable for a wide range of wetting of the substrate 202 without sacrificing sensitivity to various analytes, compared to conventional polymers.

2C is a schematic partial ablation plan view of a hybrid patch sensor 240 according to another embodiment of the present invention. 2D is a schematic side cross-sectional view of the hybrid patch sensor 240 shown in FIG. 2C. As shown in Figure 2c-d, the hybrid patch sensor 240, the lower substrate 254; Upper substrate 242; Hoop layer 244; Piezoelectric device 248; An optical fiber coil 246 having both ends 250a-b; Upper and lower buffer layers 260a-b; And two electric wires 252a-b connected to the piezoelectric device 248. The piezoelectric device 248 includes a piezoelectric layer 264; A lower conductor 262 connected to the wire 252b; And an upper conductor 266 connected to the electric wire 252a. The optical fiber coil 246 may include an optical fiber cable 258 of a winding body; And a coating layer 256. The components of the hybrid patch sensor 240 are similar to those of the counterpart of the hybrid patch sensor 200.

As in the case of the patch sensor 150, the hybrid patch sensor 240 can be attached to the main structure and / or embedded in the composite laminate. In one embodiment, the hoop layer 244 may be configured similarly to the hoop layer 198 to fill the cavity formed by the patch sensor 240 and the composite laminate.

3A is a schematic partial ablation plan view of an optical fiber patch sensor 300 according to an embodiment of the present invention. 3B is a schematic side cross-sectional view of the optical fiber patch sensor 300 taken along the D-D direction of FIG. 3A. As shown in FIGS. 3A-B, the optical fiber patch sensor 300 includes a substrate 302; Hoop layer 304; An optical fiber coil 308 having both ends 310a-b; Molding layer 316; And a coating layer 306. The optical fiber coil 308, the optical fiber cable 312 of the winding; And a coating layer 314. The material and function of each element of the optical fiber patch sensor 300 is similar to that of the counterpart of the hybrid patch sensor 200 of FIG. 2A. The diameter 313 of the innermost winding of the fiber optic cable 312 can be determined by the material properties of the fiber optic cable 312.

FIG. 3C is a schematic partial ablation plan view of an optical fiber coil 308 housed within the optical fiber patch sensor of FIG. 3A, illustrating a method of winding the optical fiber cable 312. As shown in FIG. 3C, the outermost winding of the optical fiber coil 308 starts at one end 310a and the innermost winding ends at the other end 310b. 3D is a schematic partial ablation plan view of another embodiment 318 of the optical fiber coil 308 shown in FIG. 3C. As shown in FIG. 3D, the optical fiber cable 322 is folded and wound such that its outermost windings begin to form at both ends 320a-b. The optical fiber cable 322 of the winding body may be coated with a coating layer 319.

The optical fiber coils 308 and 318 shown in Figs. 3C-D can be directly attached to the main structure and used as optical fiber coil sensors. For this reason, hereinafter, the terms "optical fiber coil" and "optical fiber coil sensor" will be used synonymously. 3E-F illustrate another embodiment of the fiber coil 308. As shown in FIG. 3E, the optical fiber coil 330 includes an optical fiber cable 334 having both ends 338a-b and wound in the same shape as the cable 312; And a coating layer 332. The optical fiber coil 330 may include a hole 336 for accommodating a fastener described later. Similarly, the optical fiber coil 340 of FIG. 3F includes an optical fiber cable 344 having both ends 348a-b and wound in the same form as the cable 322; And a coating layer 342. The coil 340 may include a hole 346 for receiving a fastener. 3G is a schematic side cross-sectional view of the optical fiber coil 330 taken along the D-D direction of FIG. 3E.

It should be noted that the sensor shown in FIGS. 3A-G can be embedded in a stack in a form similar to that shown in FIG. 1G.

4A is a schematic partial ablation plan view of a diagnostic patch washer 400 in accordance with one embodiment of the present invention. 4B is a schematic side cross-sectional view of the diagnostic patch sensor 400 taken along the E-E direction of FIG. 4A. As shown in FIGS. 4A-B, the diagnostic patch sensor 400 includes: an optical fiber coil 404 having both ends 410a-b; Piezoelectric device 406; A support element 402 for bonding and receiving the optical fiber coil 404 and the piezoelectric device 406 with an adhesive material; A pair of wires 408a-b connected to the piezoelectric device 406; And a covering disk 414 configured to cover the optical fiber coil 404 and the piezoelectric device 406.

The materials and functions of the optical fiber coil 404 and the piezoelectric device 406 are similar to those of the optical fiber coil 210 and the piezoelectric device 208 of the hybrid patch sensor 200. In one embodiment, the piezoelectric device 406 is similar to the piezoelectric device 130 except that there is no hole 403. The optical fiber coil 404 and the piezoelectric device 406 may be attached to the support element 402 using conventional epoxy. The support element 402 may have a notch 412 through which both ends 410a-b and a pair of wires 408a-b of the optical fiber coil 404 pass.

In FIGS. 4A-B, the diagnostic patch sensor 400 can act as an actuator / sensor and can include an optical fiber coil 404 and a piezoelectric device 406. In other embodiments, the diagnostic patch washer 400 may act as a sensor, and may include only an optical fiber coil 404. In other embodiments, the diagnostic patch washer 400 may act as an actuator / sensor and may include only a piezoelectric device 406.

As shown in FIGS. 4A-B, the diagnostic patch washer 400 may have a cavity 403 for receiving another fastener such as a bolt or rivet. 4C is a schematic diagram of an exemplary bolted structure 420 using a diagnostic patch washer 400 in accordance with one embodiment of the present invention. In the bolted structure 420, a pair of structures 422a-b such as plates may be fixed using a conventional bolt 424, a nut 426 and a washer 428. It is well known that the stress of the structure tends to concentrate on the bolted portion 429 and damage the structure. The diagnostic patch sensor 400 may be embedded in the bolted structure 420 and used to detect such damage.

4D is a schematic cross-sectional view of an exemplary bolted structure 430 using a diagnostic patch washer 400 in accordance with another embodiment of the present invention. In the bolted structure 430, the honeycomb / laminated structure 440 may be fixed using a conventional bolt 432, a nut 434, and a pair of washers 436 and 438. The honeycomb and laminate structure 440 includes a composite laminate 422 and a honeycomb portion 448. In order to detect damage of the structure near the bolting region, a pair of diagnostic patch washers 400a-b may be inserted into the honeycomb portion 448, as shown in FIG. 4D. A sleeve 446 is required to support the top and bottom patch washers 400a-b against the composite stack 442. In addition, a heat shield annular disk 444 may be interposed between the composite stack 422 and the diagnostic patch washer 400b to protect the washer 400b from destructive heat transfer.

As shown in FIG. 4B, the outer circumferential portion 415 of the covering disk 414 separates the optical fiber coil 404 and the piezoelectric device 406 from excessive contact load due to torque applied to the bolt 424 and the nut 426. It may have an angle of inclination to form a protective locking mechanism.

5A is a schematic diagram of an interrogation system 500 having a sensor / actuator in accordance with one embodiment of the present invention. As shown in FIG. 5A, the interrogation system 500 includes a sensor / actuator device 502 for generating and / or receiving a lamb wave signal; Two conductor wires 516; An adjusting device (508) for processing signals received by the device (502); An analog-to-digital (A / D) converter 504 for converting the analog signal into a digital signal; A computer 514 for managing the entire system 500; Amplifier 506; A waveform generator 510 for converting a digital signal into an analog lamb wave signal; And a relay switch module 512 configured to switch a connection state between the sensor / actuator device 502 and the computer 514. In general, one or more devices 502 may be connected to a relay switch 512.

The sensor / actuator device 502 comprises one of the sensors shown in FIGS. 1A-2D and 4A-D, including a piezoelectric device for generating a lamb wave 517 and receiving a lamb wave generated at another device. can do. To generate the lamb wave 517, the waveform generator 510 receives the digital signal of the waveform excited from the computer 514 (especially the analog output card included in the computer 514) via the relay switch module 512. Can be received. In one embodiment, the waveform generator 510 may be configured as an analog output card.

The relay switch module 512 may be configured as a conventional plug-in relay board. By means of a "cross-talks" linker between the actuators and the sensors, the relay switches included in the relay switch module 512 can cooperate with the computer 514 to select each relay switch in a particular order. have. In one embodiment, the analog signal generated by waveform generator 510 may be transmitted to other actuator (s) via branching wires 515.

The device 502 can function as a sensor for receiving Lamb waves. The received signal is sent to a regulator 508 that can adjust the signal voltage and filter the electrical noise to select a meaningful signal within the appropriate frequency band. The filtered signal is then sent to an analog-to-digital converter 504 that can be configured as a digital input card.

5B is a schematic diagram of an interrogation system with a sensor in accordance with another embodiment of the present invention. The interrogation system 520 includes: a sensor 522 having an optical fiber coil; Optical fiber cable 525 for connection; A laser light source 528 for providing a carrier input signal; A pair of modulators 526 and 534; Acoustooptic modulator (AOM) 530; A pair of couplers 524 and 532; A photodetector 536 for detecting an optical signal transmitted through the optical fiber cable 525; A / D converter 538; Relay switch 540; And a computer 542. The sensor 522 may be configured as one of the sensors shown in FIGS. 2A-4D having an optical fiber coil. In one embodiment, coupler 524 may connect fiber optic cable 525 to another fiber 527, which may be connected to another sensor 523.

The sensor 522, in particular the fiber coil included in the sensor 522, can act as a laser Doppler velocitimeter (LDV). The laser light source 528, preferably a diode laser, may emit an input carrier optical signal to the modulator 526. The modulator 526 may be configured as a heterodyne modulator, and splits a carrier input signal into two signals, one signal for the sensor 522 and the other for the AOM 530. do. The sensor 522 displaces the input carrier signal by the Doppler frequency corresponding to the lamb wave and transmits it to the modulator 534 which can be configured as a heterodyne synchronizer. The modulator 534 may demodulate the transmitted light to remove the carrier frequency of the light. The photodetector 536, preferably a photodiode, converts the demodulated optical signal into an electrical signal. The A / D converter 538 then digitizes the electrical signal and transmits it to the computer 542 via the relay switch module 540. In one embodiment, the coupler 532 may connect an optical fiber cable 546 connected to another sensor 544.

6A is a schematic diagram of a diagnostic network patch system (DNP) 600 installed in a master structure 610 in accordance with one embodiment of the present invention. As shown in FIG. 6A, the system 600 includes a patch 602; Transmission link 612; At least one bridge box 604 connected to the transmission link 612; Data collection system 606; And a computer 608 for managing the DNP system 600. The patch 602 may consist of the sensor / actuator device 502 of FIG. 5A or the sensor 522 of FIG. 5B, where the format of the transmission link 612 may be determined by the type of the patch 602. , Wires, optical fiber cables, or both. Typically, the main structure 610 may be made of composite or metal.

The transmission link 612 terminates at the bridge box 604. The bridge box 604 connects a plurality of patches 602 to receive a signal from an external waveform generator 510 (see FIG. 5A), and receives the received signal from an external A / D converter 504 (FIG. (See 5a). The bridge box 604 is connected via an electrical / optical cable and at the same time accommodates an adjusting device 508 (see FIG. 5A) for adjusting operating signals, filtering received signals, and converting optical fiber signals to electrical signals. can do. The data collection system 606 connected to the bridge box 604 uses a relay switch module 512 (see FIG. 5A) to relay a plurality of patches 602 and at the same time a signal received from the patches 602. Are multiplexed into the channel in a predetermined order.

It is well known that the generation and detection of lamb waves is influenced by the installation positions of actuators and sensors on the main structure. Thus, the patches 602 should be properly paired within the network structure to maximize the use of the lamb wave to identify damage.

6B is a schematic diagram of a diagnostic network patch system 620 having a strip network structure in accordance with one embodiment of the present invention. As shown in FIG. 6B, the patch system 620 may be attached to the main structure 621 and includes a patch 622; A bridge box 624 connected to the computer 626; And a transmission link 632. The plurality of patches 622 may be configured with the sensor / actuator device 502 of FIG. 5A or the sensor 522 of FIG. 5B, and the format of the transmission link 632 may be determined by the type of the patch 622. have. The transmission link 632 may be configured of an electric wire, an optical fiber cable, or both.

The computer 626 may coordinate the operation of the patch 622, which may function as an actuator and / or a sensor. Arrow 630 indicates the propagation of the lamb wave generated by patch 622. In general, defects 628 in the main structure 621 may affect the transmission pattern in the form of wave scattering, diffraction, and transmission loss of the lamb wave. The defects 628 include damage, cracks, exfoliation of composite structures, and the like. The defect 628 can be monitored by detecting a change in the transmission pattern of the lamb wave captured by the patch 622.

The network structure of the DNP system is important in the health monitoring system of a lamb wave-based structure. In the network structure of the DNP system 620, the wave-ray communication path should be uniformly randomized. The uniformity of the communication path and the distance between the patches 622 can determine the minimum detectable dimension of the defect 628 in the main structure 621. An optimized network structure with an appropriate path structure can improve the confirmation accuracy of the damaged portion without increasing the number of patches 622.

Another structure for forming the crosstalk path between the patches may consist of the pentagonal network shown in FIG. 6C. 6C is a schematic diagram of a diagnostic network patch system 640 having a pentagonal network structure in accordance with another embodiment of the present invention. The system 640 may be installed in the main structure 652, and may include a patch 642; A bridge box 644 connected to the computer 646; And a transmission link 654. The plurality of patches 642 may be configured as the sensor / actuator device 502 of FIG. 5A or the sensor 522 of FIG. 5B. In the system 640, the patch 642 can detect the defect 650 by transmitting and receiving a lamb wave indicated by arrow 648.

6D is a schematic perspective view of a diagnostic network patch system 660 installed in rivet / bolt coupled composite laminates 666 and 668 according to another embodiment of the present invention. As shown in FIG. 6D, the system 660 includes a patch 662; And a diagnostic patch washer 664, each washer connected by a pair of bolts and nuts. In FIG. 6D, the bridge box and the transmission link are not shown for simplicity. The plurality of patches 662 may be configured as the sensor / actuator device 502 of FIG. 5A or the sensor 522 of FIG. 5B. In the diagnostic network patch system 660, the patch 662 and the diagnostic patch washer 664 can detect the defect 672 by the transmission and reception of the lamb wave as indicated by the arrow 670. Normally, a defect 672 occurs near the fastener hole. The diagnostic patch washer 664 may be in communication with another adjacent diagnostic patch 662 disposed in the strip network structure, as shown in FIG. 6D. In one embodiment, the optical fiber coil sensors 330 and 340 of FIGS. 3E and 3F may be used as a substitute for the diagnostic patch washer 664.

6E is a schematic perspective view of a diagnostic network patch system 680 installed in a composite laminate 682 that may be repaired by an adhesive patch 686 in accordance with one embodiment of the present invention. As shown in FIG. 6E, the system 680 includes a plurality of patches 684 that may be configured with the sensor / actuator device 502 of FIG. 5A or the sensor 522 of FIG. 5B. 6E does not show the bridge box and the transmission link for simplicity. In the system 680, the patch 684 detects a defect 688 located between the repair patch 686 and the composite laminate 682 by transmitting and receiving the lamb wave indicated by the arrow 687. Can be.

6F is a schematic diagram illustrating one embodiment of a wireless data communication system 690 for controlling a network patch system for remote diagnostics in accordance with one embodiment of the present invention. As shown in FIG. 6F, the system 690 includes a bridge box 698; And a terrestrial communication system 694 that can be operated by the ground controller 692. The bridge box 698 may be connected to a diagnostic network patch system implemented on a host structure, such as an aircraft 696, which requires extensive structural health monitoring.

The bridge box 698 can operate in two ways. In one embodiment, the bridge box 698 may operate as a signal transmitter. In this embodiment, the bridge box 698 is an RF remote capable of transmitting micro miniature transducers and health monitoring information of the structure to the terrestrial communication system 694 via radio signals 693. Microprocessors of the measurement system. In another embodiment, the bridge box 698 may operate as a receiver of electromagnetic waves. In this embodiment, the bridge box 698 may have an assembly for receiving power from the terrestrial communication system 694 via a radio signal 693. The received power can be used to operate the DNP system installed in the structure 696. The assembly may comprise a micromachined silicon substrate having a stimulating electrode, a complementary metal oxide semiconductor (CMOS), a bipolar power regulation circuit, a hybrid chip capacitor, and a receiving antenna coil. have.

The structure of the bridge box 698 may be configured similarly to the outer layer of the main structure (696). In one embodiment, the bridge box 698 may have a plurality of honeycomb laminated structure. Here, a plurality of microstrip antennas are embedded in the outer surface of the honeycomb laminated structure of the plurality of layers, and the antennas operate as a right angle load antenna. The multi-layer honeycomb laminated structure is made of a honeycomb core, an organic material and / or an inorganic material such as e-glass / epoxy, kevlar / epoxy, graphite / epoxy, aluminum, or steel. Can be provided with a plurality of dielectric laminates. As the integrated micromachining technology rapidly develops, the dimensions and production costs of microstrip antennas can be further reduced, which can lead to a reduction in the operation / production costs of the bridge box 698 without any functional impairment.

The scope of the present invention is not limited to the use of standard Wireless Application Protocol (WAP) and wireless markup languages for structure sound wireless surveillance systems. By using the mobile Internet toolkit, the system provides a stable site that allows WAP-enabled cell phones, Pocket PCs with HTML browsers, or other HTML-enabled devices to accurately access structural status monitoring or infrastructure management. Can be rescued.

Just as the microphone array can be used to find the direction of a moving source, the sensor assembly array can be used to detect damage by measuring the difference in signal arrival time. 7A is a schematic diagram of a diagnostic network patch system 700 having sensor assemblies in a strip network structure in accordance with one embodiment of the present invention. As shown in FIG. 7A, the system 700 may be installed in the main structure 702 and includes a sensor assembly 704 and a transmission link 706. Each sensor assembly 704 has two receivers 708 and 712 and one actuator / receiver device 710. Each receiver 708 and 712 can be configured with one of the sensors shown in FIGS. 1A-4D, and the actuator / receiver device 710 is one of the sensors shown in FIGS. 1A-2D and 4A-D. A piezoelectric device for lamb wave generation can be provided. When the actuator / receiver 710 of the sensor assembly 704 transmits a lamb wave, the adjacent sensor assembly 704 has all three elements, namely the actuator / receiver device 710 and the receivers 708 and 712. To receive the lamb wave. By using all three elements as the receiving unit, each sensor assembly 704 can receive a more refined lamb wave. In addition, by measuring the time difference of arrival between the three elements, the direction of the defect 714 can be extracted with high accuracy.

7B is a schematic diagram of a diagnostic network patch system 720 having sensor assemblies in a pentagonal network structure in accordance with another embodiment of the present invention. As shown in FIG. 7B, the system 720 can be installed in the main structure 722 to detect a defect 734 and includes a sensor assembly 724 and a transmission link 726. Each sensor assembly 724 is similar to the sensor assembly 704.

8A is a schematic diagram of a sensor assembly 800 having an optical fiber coil in series connection according to an embodiment of the present invention. The sensor assembly 800 is similar to the sensor assembly 704 of FIG. 7A and includes two sensors 804 and 808 and one actuator / sensor 806. In this structure, the input signal can enter the sensor via one end 810a, and the output signal from the other end 810b is the contribution of the input signal and the three sensors 804, 806 and 808. Can be the sum of. In one embodiment, the signal output from each sensor can be separated from other signals using a wavelength-based de-multiplex technique.

8B is a schematic diagram of a sensor assembly 820 having optical fiber coils connected in parallel in accordance with one embodiment of the present invention. The sensor assembly 820 is similar to the sensor assembly 704 of FIG. 7A and includes two sensors 824 and 828 and one actuator / sensor 826. In this structure, the input signal can enter the three sensors through the three ends 830a, 832a, and 834a, respectively, and the output signals from the other ends 830b, 832b, and 834b are input signals and three sensors. 824, 826, and 828 can be the sum of the contributions.

In FIGS. 8A-B, the sensors 804, 808, 824, and 828 are shown as an optical fiber coil sensor 308. However, for those skilled in the art, each sensor 804, 808, 824, and 828 can be configured as one of the sensors shown in FIGS. 1A-4D, and the intermediate sensors 806 and 826 are shown in FIGS. 1A-2D and 4A-D. It can be configured as one of the sensors, it is obvious that it has a piezoelectric device for generating a lamb wave. In addition, the sensor assemblies 800 and 820 may be interposed in the composite laminate in the same form as shown in FIG. 1G.

9 is a curve diagram 900 of actuator and sensor signals in accordance with one embodiment of the present invention. In order to generate the lamb wave, the actuator signal 904 may be applied to an actuator, such as the patch sensor 100 of FIG. 1A. The actuator signal 904 may be configured as a toneburst signal having a plurality of wave peaks having the highest amplitude in the middle of the waveform. The actuator signal 904 can be designed by using a Hanning function for various waveforms and has its intermediate frequency of 0.01 MHz to 1.0 MHz. The actuator receives the actuator signal 904 to generate a lamb wave having a specific excitation frequency.

Signals 912a-n represent sensor signals received by the plurality of sensors. As shown, each signal 912 is separated by wave packets 926, 928 separated by signal extracting windows (or signal extracting envelopes) 920, 922, and 924, respectively. And 930. These wave bundles 926, 928 and 930 may have different frequencies due to the dispersion mode at the position of the sensor. The signal separation window 916 is applied to identify a lamb wave signal from each sensor signal. The wave _bundles 926, 928, and 930 correspond to the basic symmetry mode S ₀ , the reflection mode S _{0 _ ref} , and the basic asymmetry mode A ₀ , respectively. The reflection mode S _{0_ref} represents lamb wave reflection from the boundary of the main structure. Basic shear modes S ₀ ′ and other higher modes can be observed. However, these are not shown in FIG. 9 for the sake of simplicity.

Portions 914 of sensor signal 912 are electrical noise due to toneburst actuator signal 904. In order to separate the portion 914 from the sensor signal 12, a masking window 918, which is a sigmoid function that is postponed during the operation time, is used as a threshold function. Can be applied to). Next, wave speeds 926, 928, and 930 may be extracted from the sensor signals of 912 using moving wave-envelope windows 920, 922, and 924 along the time series of each sensor signal. The envelope windows 920, 922, and 924 apply a hill-climbing algorithm that searches for peaks and valleys of the sensor signal 912, and interpolates the searched data points on the time axis. can be determined by interpolating. If the size of the nearest data point is smaller than the size of the current data point until the size comparison of the wave in the forward and backward directions is made continuously for all data points of the wave signal, the data point in the wave signal The size and location can be stored. Once the envelope of the wave signal is obtained, each envelope is divided into sub-envelope windows 920, 922 and 924 at a time interval corresponding to that of the lamb wave mode. The server envelope windows 920, 922, and 924 can be applied to extract wave speeds 926, 928, and 930 by moving along the entire time history of each measured sensor signal 912.

While the present invention has been described with reference to specific embodiments, it is to be understood that the foregoing embodiments are directed to preferred embodiments of the invention, and that the invention is capable of modification without departing from the spirit and scope described in the appended claims.

Sensors or systems for health monitoring of structures of the present invention can be easily installed in existing structures and / or new structures, and provide effective online techniques for condition diagnosis, state classification, and condition prediction of structures with minimal human intervention. Can provide.

Claims (14)

A wave generator coupled to the structure and operative to generate a wave signal propagating through the structure; A plurality of optical fiber sensors applied to the structure, the optical fiber sensor for forming a communication path (communication path) for transmitting a wave signal between the optical fiber sensor and the derivative group; At least one electronic module operative to generate an input sensor signal and to transmit the input sensor signal to at least one optical fiber sensor, wherein each optical fiber sensor applies the wave signal to the input sensor signal to provide an output sensor signal; An electronic module operable to generate an information signal in response to the output sensor signal; Signal processing unit; A relay switch array module having a plurality of relay switches, wherein one of the relay switches operates to relay the information signal to the signal processing unit, wherein the signal processing unit generates a digital sensor signal in response to the information signal. A relay switch array module operative to transmit said digital sensor signal to computer means; And A interrogation system for monitoring the health status of the structure, comprising: a first coupler coupled to branch a portion of the input sensor signal and operative to transmit a portion of the input sensor signal to another optical fiber sensor; interrogation system). delete The optical sensor of claim 1, further comprising a second coupler for optically interconnecting the plurality of optical fiber sensors and the electronic module, wherein the second coupler is an output sensor from an optical fiber sensor different from the output sensor signal from the optical fiber sensor. Interrogation system for monitoring the health of the structure, characterized in that it operates to add a signal. The method of claim 1, wherein the electronic module, A light source for generating an optical signal; A first modulator responsive to the optical signal, the first modulator operative to modulate the optical signal and generate the input sensor signal; An acoustic optical modulator (AOM) operative to respond to the input sensor signal and to generate a modulated signal; A second modulator responsive to the modulated signal and the output sensor signal, the second modulator operative to extract an information light signal corresponding to the wave signal; And And a photo detector operable to respond to the information light signal and to generate the information signal. The interrogation system for health condition monitoring of a structure according to claim 4, wherein the first modulator is a heterodyne modulator and the second modulator is a heterodyne synchronizer. The interrogation system for health condition monitoring of a structure according to claim 1, wherein said optical fiber sensor forms a network arranged along at least two substantially parallel lines. 7. The interrogation system for health condition monitoring of a structure according to claim 6, wherein the network is configured to provide a uniformly random communication path between the two lines. The interrogation system for monitoring the health status of a structure according to claim 1, wherein the optical fiber sensor is arranged to form a pentagonal network. The interrogation system of claim 8, wherein the pentagonal network is configured to provide a uniformly random communication path within the pentagonal network. 9. The interrogation system for health condition monitoring of a structure according to claim 8, wherein the pentagonal network configuration surrounds an adhesive patch attached to the structure and provides a communication path concentrated on the adhesive patch. The interrogation system for health condition monitoring of a structure according to claim 1, wherein said signal processing unit comprises an analog-to-digital converter. The interrogation system for health condition monitoring of a structure according to claim 1, further comprising a bridge box for optically interconnecting the plurality of optical fiber sensors and the electronic module. The method of claim 1, wherein each of the plurality of optical fiber sensors, Optical fiber cable rolls; And It includes a coating layer coated on the optical fiber cable roll body, A predetermined tensile force is applied during the winding process of the optical fiber cable roll body, and the coating layer maintains the tensile stress applied to the optical fiber cable roll body during operation of the optical fiber sensor. The interrogation system of claim 1, wherein the wave signal comprises at least one of a lamb wave and a vibration wave.

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