Pressure sensor arrangement and method of manufacture of the same

Abstract

Aspects concern a pressure sensor arrangement comprising: a base structure, the base structure defining a cavity; a diaphragm, the diaphragm positioned on the base structure in a manner such as to deform under an applied pressure, the deformation toward or into the cavity; a first Fiber Bragg Grating (FBG) disposed on a first side of the diaphragm, and a second FBG disposed on an opposing second side of the diaphragm relative to a neutral plane of the diaphragm, the first FBG and the second FBG forming an optical fiber sensor; wherein upon the application of the applied pressure, the first FBG and the second FBG experience opposing strain relative to each other.

Description

PRESSURE SENSOR ARRANGEMENT AND METHOD OF MANUFACTURE OF THE SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] The application claims the benefit of priority of Singapore patent application No.10202500807R, filed on 27 March 2025, the content of it being hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The disclosure relates to a pressure sensor arrangement and a method of manufacture thereof.BACKGROUND

[0003] The following discussion of the background is intended to facilitate an understanding of the present disclosure only. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known, or is part of the common general knowledge of the person skilled in the art in any jurisdiction as of the priority date of the disclosure

[0004] In relatively larger water vessels, particularly those having aft-located deckhouses and bridges, slamming events at the bow may go unnoticed by the crew. Such slamming events subject the vessel structure to high loads and significantly contribute to structural fatigue.

[0005] Accurate detection of bow emergence and slamming pressures requires strategically positioned pressure sensors. In addition, since pressure-induced strain and temperature both cause wavelength shifts, temperature effects can reduce measurement accuracy.

[0006] There therefore exists a need for a pressure sensor that is able to measure pressure accurately, compensates for temperature effects, and is suitable for use in underwater operation.SUMMARY]0007] A technical solution is provided in the form of a pressure sensor arrangement, the pressure sensor arrangement comprising a diaphragm configured to deform under pressure; a base structure, whereby temperature-induced wavelength shifts are compensated and pressure sensitivity is increased relative to a single FBG.

[0008] The present disclosure relates to a pressure sensor arrangement.

[0009] In some embodiments, there may comprise a pressure sensor arrangement comprising a base defining a cavity, a diaphragm covering the cavity, and a pair of Fiber Bragg Gratings (FBGs) pre-embedded within CFRP and bonded to opposing sides of the diaphragm symmetrically about its neutral plane, such that opposing-sign strain is induced under an applied pressure. In such embodiments, the base is a single-piece 3D-printed structure sealed to the diaphragm by a continuous waterproof seal; the total thickness is < 3 mm; the optical fiber traverses the diaphragm diagonally; and a plurality of the arrangements can be cascaded and interrogated optically for slamming detection.

[0010] According to an aspect of the present disclosure there is provided a pressure sensor arrangement comprising: a base structure, the base structure defining a cavity; a diaphragm, the diaphragm positioned on the base structure in a manner such as to deform under an applied pressure, the deformation toward or into the cavity; a first Fiber Bragg Grating (FBG) disposed on a first side of the diaphragm, and a second FBG disposed on an opposing second side of the diaphragm relative to a neutral plane of the diaphragm, the first FBG and the second FBG forming an optical fiber sensor; wherein the first FBG and the second FBG are positioned in a manner such that upon the application of the applied pressure, the first FBG and the second FBG experience opposing strain relative to each other.

[0011] In some embodiments, upon the application of the applied pressure, the first FBG experiences tensile strain and the second FBG experiences compressive strain.

[0012] In some embodiments, at least one of the first FBG and / or the second FBG is embedded within a carbon fiber reinforced polymer (CFRP) prepreg bonded to the diaphragm.

[0013] In some embodiments, the pressure sensor arrangement further comprises a waterproof sealant, wherein the waterproof sealant is applied around an interface between the diaphragm and the base structure.

[0014] In some embodiments, the diaphragm comprises a polymer sheet selected from polycarbonate (PC) or polyvinyl chloride (PVC).]0015] In some embodiments, the base structure comprises a base sheet and a hollow frame layered on the base sheet, the hollow frame defining the cavity, and the diaphragm is dimensioned to form a cover over the hollow frame.

[0016] In some embodiments, the diaphragm is dimensioned to cover the cavity and form a pressure chamber, the diaphragm being configured to deform into the cavity when pressure is applied to a first side of the diaphragm.

[0017] In some embodiments, the first FBG and second FBG are directly bonded to the diaphragm using an adhesive layer.

[0018] In some embodiments, each of the first FBG and the second FBG is positioned at or near a central region of the diaphragm.

[0019] In some embodiments, the adhesive layer is disposed between each of the first FBG, the second FBG, and the diaphragm, and wherein a protective epoxy layer covers at least a grating region of each of the first FBG and the second FBG.

[0020] In some embodiments, the first FBG has a first Bragg wavelength and the second FBG has a second Bragg wavelength different from the first Bragg wavelength.

[0021] In some embodiments, the first Bragg wavelength is a shorter wavelength than the second Bragg wavelength.

[0022] According to another aspect of the present disclosure there is provided a method of manufacturing a pressure sensor arrangement, the method comprising: forming a base structure; defining a cavity on the base structure; providing a flexible sheet configured as a diaphragm; positioning the diaphragm on the base structure in a manner such as to deform under an applied pressure, the deformation toward or into the cavity; and disposing a first Fiber Bragg Grating (FBG) disposed on a first side of the diaphragm, and a second FBG on an opposing second side of the diaphragm relative to a neutral plane of the diaphragm, the first FBG and the second FBG fonning an optical fiber sensor; wherein upon the application of the applied pressure, the first FBG and the second FBG experience opposing strain relative to each other.

[0023] In some embodiments, the method further comprises securing the first FBG and the second FBG to the diaphragm, using an adhesive.

[0024] In some embodiments, defining the cavity on the base structure further comprises forming a hollow frame defining the cavity, bonding the diaphragm to the hollow frame using a waterproof adhesive so as to cover the cavity; and applying a waterproof sealing layer over at least part of a grating region defined by the first FBG and the second FBG.

[0025] In some embodiments, the base structure, the hollow frame, and the diaphragm are substantially square.

[0026] In some embodiments, the base structure has dimensions of approximately 28 millimetres (mm) x 28 mm and a thickness of approximately 0.4 mm; the hollow frame has outer dimensions of approximately 28 mm x 28 mm and inner dimensions of approximately 20 mm x 20 mm with a thickness of approximately 0.4 mm; and the diaphragm has dimensions of approximately 28 mm x 28 mm and a thickness of approximately 0.2 mm.

[0027] According to another aspect of the present disclosure there is provided a slamming event monitoring system for a marine vessel, comprising: at least one pressure sensor arrangement as described, the at least one pressure sensor arrangement mounted at a bow region of the marine vessel; an optical interrogator operatively connected to the at least one pressure sensor arrangement to receive wavelength shift signals from the first FBG and the second FBG; and a processing unit configured to: determine pressure data from the wavelength shift signals; and detect one or more slamming events based on the pressure data.

[0028] In some embodiments, the processing unit is further configured to: record pressure data over a time period; establish one or more loading profiles based on the recorded pressure data; predict structural fatigue life of the marine vessel based on the loading profiles; and trigger a warning signal when one or more slamming events or a predetermined loading condition is detected.

[0029] In some embodiments, a plurality of the pressure sensor arrangement are optically cascaded along a common optical fiber to form a pressure sensor array; the optical interrogator is configured to interrogate the pressure sensor array; and the processing unit is configured to: determine spatially distributed pressure data at a plurality of locations along the bow region, and detect one or more slamming events based on the spatial pressure distribution.

[0030] In some embodiments, the diaphragm comprises a thickness in a range of 0.10 mm to 0.50 mm, and a Young’s modulus of more than or equal to 2 Gigapascal (GPa), and each FBG is embedded within a 2 to 4-ply CFRP laminate bonded to the diaphragm, the base structure being additively manufactured with a wall thickness of more than or equal to 1 mm.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The disclosure will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:- FIG. 1 illustrates a side view of a pressure sensor arrangement according to various embodiments.- FIG. 2 illustrates perspective views of a base structure and diaphragm of the pressure sensor arrangement based on a diaphragm structure.- FIGS. 3A to 3C are cross-sectional views of the pressure sensor arrangement, with particular emphasis on the positioning of a first FBG and a second FBG, according to various embodiments of the present disclosure.- FIG. 4 illustrates an embodiment of the fabrication process of the pressure sensor arrangement according to various embodiments of the present disclosure.- FIGS. 5 A to 5D illustrate two possible embodiments of the pressure sensor arrangement according to various embodiments of the pressure disclosure. FIG. 5A and 5C illustrate a three-piece embodiment, and FIG. 5B and 5D illustrate a two-piece embodiment. - FIGS. 6A to 6D show perspective views of completed pressure sensor arrangement according to various embodiments of the pressure disclosure.- FIG. 7 is a generalized flow chart of a method for manufacturing a pressure sensor arrangement according to some embodiments.- FIG. 8 illustrates an embodiment of a slamming event monitoring system for a marine vessel according to some embodiments.DETAILED DESCRIPTION

[0032] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure. Other embodiments may be utilized and structural, logical changes may be made without departing from the scope of the disclosure The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments

[0033] Embodiments described in the context of one of the systems or methods are analogously valid for the other systems or methods.

[0034] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments,even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0035] In the context of some embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0036] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0037] As used herein, the term “at least substantially” may include “exactly” and a reasonable variance.

[0038] As used herein, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance.

[0039] As used herein, the term “device” may be understood to refer to any apparatus, equipment, or component, whether standalone or integrated, that performs a specific function or set of functions. This includes, but is not limited to, mechanical, electrical, electronic, optical, or electromechanical systems, subsystems, and assemblies. A device may comprise one or more components, modules, or units that are designed to interact with each other to achieve a particular purpose.

[0040] As used herein, the term “configured to” broadly refers to the design, arrangement, or adaptation of a system, device, component, or module to perform a specific function or achieve a particular outcome. The term includes both hardware and / or software implementations wherein in a hardware implementation, the physical components are arranged, programmed, or structured to carry out the intended function(s), and in the context of programming and software, a device is operable under executable instructions (e.g., software, firmware) to perform the specified function(s) when executed by one or more processors. The resultant configuration allows the system or component to perform the stated function, either inherently or after suitable programming or activation, without requiring substantial modifications to its structure or operational logic.

[0041] As used herein, the term “pressure sensor” refers to a device configured to detect and convert a pressure stimulus into a measurable output signal, including but not limited to electrical, optical, or mechanical signals. The pressure may include: static pressure, dynamic pressure, fluid pressure, hydrostatic pressure, wave-induced pressure, differential pressure, and / or absolute pressure. The output signal may include optical wavelength shift, opticalintensity variation, electrical voltage, electrical current variation, frequency shift, and / or digital signal.

[0042] As used herein, the term “diaphragm” refers to a thin, flexible membrane or plate configured to deform in response to an applied pressure differential. The diaphragm may be: planar or curved, circular, square, rectangular, polygonal, or irregular, metallic, polymeric, composite, and / or multilayer, clamped, supported, bonded, or integrally formed with a base structure. Deformation may include one or more of: elastic bending, deflection into a cavity, and / or a tensile and compressive strain relative to a neutral axis

[0043] As used herein, the term “cavity” or “chamber” refers to a partially or fully enclosed space bounded by structural walls and configured to receive diaphragm deflection under pressure. The cavity may contain air, gas, fluid, or vacuum, be sealed or vented, be formed by moulding, machining, additive manufacturing, or assembly, and / or may be integral with or attached to a base structure.

[0044] As used herein, the term “Fiber Bragg Grating (FBG)” refers to an optical sensing element comprising a periodic or quasi-periodic modulation of refractive index along a core of an optical fiber, the modulation being configured to reflect a selected wavelength band (Bragg wavelength) while transmitting other wavelengths. The reflected Bragg wavelength is responsive to variations in one or more physical parameters, including axial strain, temperature, mechanical deformation, and / or pressure-induced strain acting on the optical fiber. An FBG may be formed, for example, by exposure of the optical fiber core to ultraviolet (UV) radiation, and may be provided in various forms including uniform, chirped, and / or phase-shifted configurations. The FBG may further be arranged in different deployment configurations, including being embedded within a structure, bonded to a surface, provided with a coating, or arranged as a bare optical fiber. The term “FBG” may be used interchangeably with the term “FBG sensor”.

[0045]

[0046] As used herein, the term “neutral plane” (or “neutral axis”) refers to the plane within a bending structure at which longitudinal strain is zero during flexural deformation. In some embodiments, when under deformation, regions above the neutral plane experience compression, and regions below experience tension (or vice versa).

[0047] As used herein, the term “temperature cancellation” refers to reduction or elimination of temperature-induced wavelength shift components in the output of a dual-FBGarrangement, achieved by disposing two FBGs on opposing sides of a deformable diaphragm such that both FBGs are subjected to substantially identical temperature variations while experiencing opposite-signed strain during diaphragm bending, whereby differential comparison of the wavelength shift signals suppresses temperature-induced contributions.

[0048] As used herein, the term “embedded” refers to placement of a component within and at least partially surrounded by another material such that mechanical coupling occurs between the component and the surrounding material. The embedding may include a full encapsulation, a partial encapsulation, lamination between plies, and / or co-curi ng within composite layers.

[0049] In the following, embodiments will be described in detail.

[0050] According to an aspect of the present disclosure and with reference to FIG. 1, there is provided a pressure sensor arrangement 100 comprising: a base structure 110, the base structure 110 defining a cavity 112; a diaphragm 120, the diaphragm 120 positioned on the base structure 110 in a manner such as to deform under an applied pressure P, the deformation toward or into the cavity 112; a first FBG sensor 130A disposed on a first side of the diaphragm 120, and a second FBG 130B disposed on an opposing second side of the diaphragm 120 relative to a neutral plane of the diaphragm, the first FBG 130A and the second FBG 130B forming an optical fiber sensor; wherein upon the application of the applied pressure P, the first FBG and the second FBG experience opposing strain relative to each other.

[0051] FIG. 2 shows an embodiment of a base structure 110 and diaphragm 120, without showing the FBG sensor(s) 130A, 130B. The diaphragm 120 may be a water pressure sensitive diaphragm, and may be fixed on an elastic based structure formed from or of a polymer (e.g. polycarbonate (PC)). A varying water pressure may cause the diaphragm 110 to deform or change its shape, thereby causing strain variations to the FBGs, which generates wavelength shift signals. The flexible base structure 100 can be molded, or manufactured based on additive manufacturing methods (e.g. 3D printed), shaped and / or dimensioned according to a surface the base structure 100 and diaphragm 110 is attached to. In some embodiments, the surface may be, or form part of, a marine vessel structure, such as an arbitrary ship / floater structures with one or more curvatures. In some embodiments, the thickness of the base structure 100 may be thin, i.e less than or equal to 1 millimeters (mm), which minimizes interference to the water profiling along underwater vessels.

[0052] FIG. 3 A to FIG. 3C illustrate the mounting of the first FBG sensor 130A, and the second FBG sensor 130B, on two opposing sides of a diaphragm 110. In some embodiments,the two opposing side may be a top side and a bottom side of the diaphragm 110. It may be appreciated that temperature compensation may be achieved by mounting the first FBG sensor 130A and the second FBG sensor DOB (the two sensors may have the same or different Bragg wavelengths) on both sides of the diaphragm in a symmetrical arrangement. When a pressure, such as a wave pressure, is applied, one FBG sensor may experience tension (tensile strain) and the other FBG sensor may experience compression (compressive strain). The two FBG sensors may be arranged symmetrical to a neutral plane of the diaphragm, and both the FBG sensors 130A, BOB, may experience similar surrounding temperature With such a configuration shown in FIG. 3, the sensitivity of the FBG pressure sensor may at least be doubled. In addition, any temperature effect can be compensated due to the symmetrical positioning of the FBG sensors BOA, BOB, as compared to using a single FBG sensor or structure.

[0053] In some embodiments, a thin layer of epoxy A 302 (such as super glue) may be applied across the FBG region, for each of the FBG sensor BOA and FBG sensor BOB, to ensure that the pair of first and second FBG sensors BOA, BOB is tightly bonded to the diaphragm 110 for pressure induced strain to be properly transferred to the FBG sensors. A thin layer of adhesive, for example a waterproof epoxy adhesive, is applied over the epoxy A 302 on the FBG sensor BOA to secure the FBG sensor BOA to the diaphragm 120 and to prevent detachment when exposed to water during operation. In some embodiments, the waterproof epoxy adhesive may comprise an epoxy-based coating (e.g., ELEP coat LSS-520MH).

[0054] In some embodiments, a waterproof soft silicone adhesive (M-704) is applied between diaphragm 120 and the base structure 110 to prevent water from entering the diaphragm structure during operation. A waterproof epoxy B is applied proximate, e.g. surrounding of the FBG sensor unit (at the thickness direction) to further enhance the structural integrity of the sensor unit.

[0055] FIG. 4 illustrates a fabrication process 400 of the pressure sensor arrangement fabrication procedure of a temperature compensated FBG Pressure Sensor according to an embodiment. The flexible material used in the fabrication process may include, but is not limited to, Polycarbonate (PC) and Polyvinyl Chloride (PVC). FIG. 4 shows the sequential assembly of structural components identified as Item A, Item B, Item C, and Item D.

[0056] In step 402, a square PC sheet, having dimensions of 28 millimeters (mm) x 28 mm, and thickness tl = 0.4 mm, may be used as the base structure 110 of a diaphragm 120. This may be referred to as Item A. This item A component provides mechanical support and forms the lower boundary of the cavity in later assembly.

[0057] In step 404, FIG. 4 next shows a hollow square frame bonded onto Item A to form Item B. A hollow square shape having outer dimensions of 28 mm x 28 mm, inner dimension of 20 mm x 20 mm, and thickness t2 = 0.4 mm of the same PC material may be cut. The hollow square shape is then placed on the base structure 110 with a thin layer of waterproof epoxy as adhesive to form Item B. In summary, the hollow frame defines an internal cavity 112, has an outer dimension substantially matching the base sheet, and has a central opening forming the cavity 112, and is bonded to the base sheet using a waterproof epoxy layer. This structure defines the cavity into which the diaphragm will later deform.

[0058] In step 406, item C is fabricated as a diaphragm sheet or cover. Item C comprises a thin flexible sheet, for example, PVC or other flexible material. This may be formed by another piece of thin flexible sheet, such as PVC, having dimension of 28 mm x 28 mm, with thickness t3 = 0.2 mm, to be used as a diaphragm 120 of the FBG pressure sensor (Item C)

[0059] In step 408, a pair of bare FBGs - FBG 130A on top, FBG 130B at the bottom, are positioned near or proximate a center region of item C. The grating region of each FBG is then covered with the thin layer of epoxy 302. Item C, i.e. the diaphragm 120, may then be positioned onto item B with the thin layer of waterproof epoxy 304 as adhesive, and affixed firmly. The thin layer of waterproof epoxy 304 may be a ELEP coat: LSS-520MH which is applied on top of the epoxy 302 of the FBG sensor 130A, as well as the surrounding of the sensor unit (at the thickness direction). It is appreciable that the temperature compensated FBG pressure sensor is formed, indicated as Item D.

[0060] It may be appreciable that FIG.4 depicts a three-piece embodiment in which the diaphragm may be directly bonded and the FBGs are bonded to the diaphragm. In contrast, FIG. 5B and FIG. 6 illustrate a two-piece embodiment comprising a single 3D-printed base and a diaphragm, with each FBG embedded within a CFRP prepreg prior to bonding to opposing sides of the diaphragm. The two-piece embodiment may address hysteresis and water ingress and simplifies fabrication.

[0061] FIG. 5A to FIG 5D show various views (including side views) of two possible embodiments. FIG. 5A relates to a three-piece embodiment, based on the earlier embodimentdepicted in FIG. 4. To avoid potential sensor hysteresis and water seepage, and to simplify the fabrication process for FBG pressure sensors, the proposed design of FIG. 5A can be restructured as illustrated in FIG. 5B and FIG. 6.

[0062] FIG. 5A and FIG. 5C show the earlier three-piece structural configuration. The configuration comprises a base structure 110, a hollow frame 115 positioned on the base structure 110 to define the cavity 112; and a diaphragm 120 bonded over the hollow frame 115.

[0063] FIG. 5B and FIG. 5D show an alternative embodiment of the pressure sensor arrangement 100A, in relation to a two-piece design. It is contemplated that the two-piece design may be used to address hysteresis effect and water seepage issues. FIG. 5B shows a base structure 110A defining the cavity 112, wherein the base structure 110A may be a singlebased 3D-printed structure, combined with waterproof sealant 502 around the diaphragm layer 120 and the base structure 110A. In some embodiments, the base structure 110A may be fabricated or manufactured based on additive manufacturing, for example, 3D-printing methods.

[0064] It may be appreciable that the arrangement of FIG. 5B and FIG. 5D may accelerate sensor fabrication and effectively minimize or prevent water from entering the central air void. In the embodiment shown in FIG. 5B, each FBG sensor 130A, 130B, may be embedded inside a two-ply, small rectangular carbon fiber-reinforced polymer (CFRP) prepreg 510, which, after curing, is bonded to the diaphragm 120 using super glue 520, shown beneath the diaphragm, and / or UV-curable epoxy 530, shown above the diaphragm. Such an arrangement may resolves any hysteresis issue due to non-linear properties causing by direct bonding between the grating fiber and plastic material. To enhance performance and maintain linear behavior of the pressure sensor arrangement 100, the two-FBG pair configuration may be embedded in small rectangular CFRP prepregs, leveraging the compatibility between grating fibers and the composite material.

[0065] In some embodiments, the first FBG sensor 130A has a first Bragg wavelength and the second FBG sensor BOB has a second Bragg wavelength different from the first Bragg wavelength.

[0066] The first Bragg wavelength is a shorter wavelength than the second Bragg wavelength. After curing, a shorter-wavelength FBG embedded in the CFRP is placed on a top portion of the diaphragm sheet 120, while the longer-wavelength FBG is attached to a bottomportion of the diaphragm sheet 120 Such a symmetrical placement may be used to ensure improved sensitivity and performance of the FBG-based pressure sensor.

[0067] FIG. 6A shows a perspective view of the embodiment of FIG. 5B, depicting the base structure 110A, the diaphragm 120, and an optical fiber 610 running through the composite 620. The composite 620 comprises the FBGs 130A, 130B, and the CFRP prepregs 510. It may be seen that the optical fiber 610 runs diagonally across two comers of the diaphragm 110.

[0068] FIG. 6B shows another perspective view of a complete pressure sensor with the cavity 112 visible, and a side view of the FIG. 6A.

[0069] FIG. 6C shows an example of the embodiment 100A with some thickness dimensions in millimeters (mm).

[0070] FIG. 6D illustrates the 3D printed base structure 110A with non-limiting dimensions.

[0071] The structural setup of the embodiment 100A facilitates effective temperature compensation When subjected to an applied pressure, such as wave pressure, the bottom FBG sensor 130B may undergo pressure-induced tension (tensile strain), while the top FBG sensor 130A may experience pressure-induced compression (compressive strain), with both exposed to similar temperatures. Consequently, the pressure sensitivity of the FBG pressure sensor doubled, and the temperature effect could be offset, in comparison to a single FBG structure. As a result, the hysteresis issue can be resolved.

[0072] Further description of the functions of the various elements or components according to some embodiments are described as follows.

[0073] Diaphragm 120: Serving as the primary sensing element, the diaphragm may be a thin, flexible membrane that deforms when subjected to pressure variations. The degree of deformation is directly proportional to the applied pressure. This fundamental diaphragm structure serves as the foundation for various pressure sensor designs, allowing for customization through material selection, dimensions, and sensing technologies to suit different applications.

[0074] Cavity or Chamber 112: The diaphragm 120 may be an integral part of a sealed cavity or chamber 112. Pressure is applied to one side of the diaphragm, causing it to flex into the cavity or chamber. The sensor measures the pressure within this enclosed space. The base structure can be molded, or 3D printed, making it adaptable to arbitrary ship and floater structures with varying curvatures Its thin profile (~ 3mm) minimizes interference with water profiling along underwater vessels.

[0075] Sensing Element: This component comprises an optical fiber with the pair of FBGs 130A, 130B. Both FBGs are pre-embedded onto a thin layer of CFRP prepregs. Upon curing, the FBG with a shorter wavelength is affixed to the upper surface of the diaphragm sheet, while the FBG with a longer wavelength is attached to the lower surface, as depicted in Figure 3. This deliberate arrangement ensures the symmetrical placement of these two FBGs with respect to the diaphragm sheet. Temperature compensation is achieved by mounting two CFRP-embedded FBGs on both sides of the diaphragm, which can take various shapes such as circular, square, or rectangular. When subjected to wave pressure, one FBG experiences tension while the other experiences compression, symmetrically relative to the neutral plane — the diaphragm sheet. Both FBGs encounter similar temperature conditions. This configuration effectively doubles the sensitivity of the FBG pressure sensor while compensating for temperature effects, surpassing the capabilities of a single FBG structure. The CFRP-embedded FBGs also ensure linear response of the FBG sensor.

[0076] Support Structure: The diaphragm is securely affixed to the pressure chamber, which can be a 3D printed cavity. Its edges are reinforced with epoxy and waterproof adhesive to maintain its shape and enable it to return to its original position once the pressure is relieved. The surrounding waterproof adhesive further bolsters the structural integrity of the sensor unit, preventing water intrusion into the diaphragm structure during operation.

[0077] According to another aspect of the present disclosure and with reference to FIG. 7, there is provided a generalized flowchart depicting a method of manufacturing a pressure sensor arrangement 700, the method comprising:

[0078] Step S701 : forming a base structure;

[0079] Step S702: defining a cavity on the base structure;

[0080] Step S703: providing a flexible sheet configured as a diaphragm;

[0081] Step S704: positioning the diaphragm on the base structure in a manner such as to deform under an applied pressure, the deformation toward or into the cavity; and

[0082] Step S705 : disposing a first FBG on a first side of the diaphragm, and a second FBG on an opposing second side of the diaphragm relative to a neutral plane of the diaphragm, the first FBG and the second FBG forming an optical fiber sensor in a manner such that upon the application of the applied pressure, the first FBG and the second FBG experience opposing strain relative to each other.

[0083] According to another aspect of the present disclosure there is provided a monitoring system using the pressure sensor arrangement 100, or 100A. The monitoring system may be used for various industry applications.

[0084] FIG. 8 illustrates an embodiment of a slamming event monitoring system 800 for a marine vessel, comprising at least one pressure sensor arrangement 100, 100A, the at least one pressure sensor arrangement 100, 100A may be mounted at a bow region of the marine vessel. In the embodiment shown in FIG. 8, there comprises a plurality of pressure sensor arrangement 100, 100A.

[0085] The system 800 may further comprise an optical interrogator 810 operatively connected to the at least one pressure sensor arrangement 100. 100A to receive wavelength shift signals from the first FBGs 130A and the second FBGs 130B associated with each pressure sensor arrangement 100, 100A, and a processing unit 820 configured to: determine pressure data from the wavelength shift signals; and detect one or more slamming events based on the pressure data. In some embodiments, the processing unit 820 is further configured to: record pressure data over a time period; establish one or more loading profiles based on the recorded pressure data; predict structural fatigue life of the marine vessel based on the loading profiles; and trigger a warning signal when one or more slamming events or a predetermined loading condition is detected.

[0086] In some embodiments, a plurality of the pressure sensor arrangement 100, 100A are optically cascaded along a common optical fiber to form a pressure sensor array; the optical interrogator 810 is configured to interrogate the pressure sensor array; and the processing unit 820 is configured to: determine spatially distributed pressure data at a plurality of locations along the bow region, and detect one or more slamming events based on the spatial pressure distribution.

[0087] The optical interrogator 810 may be a FBG interrogator for the processing of the sensed data. Such an arrangement may combine precision, symmetry, and robustness to create a relatively high-performance pressure sensor arrangement 100, 100A, with improved sensitivity, linearity, and temperature compensation capabilities.

[0088] It is appreciable that the packaging approach, involving the embedding of FBGs onto carbon fiber reinforced composite (CFRP) prepreg before affixing them to a 3D printed diaphragm structure, may improve pressure sensor performance. Such improvements may comprise one or more of the following: Drastic reduction in the impact of temperature on FBGpressure sensors; remarkable enhancement in pressure response linearity (R2> 99%); potential hysteresis issue and a water seepage problem can be resolved; achievement of pressure sensitivity of < 50 Pa / pm with temperature compensation.

[0089] In some embodiments, the pressure sensor arrangement 100, 100 A based on the above described embodiments may also be used for sensing other vibration induced signals such as noise sensing. In addition, due to the relatively passive nature of the FBG sensors, such application can be used in high corrosive or high EMI environment. A list of potential applications for the pressure sensor arrangement 100, 100A according to the present disclosure are as follows.• Aerospace Industry, for example, for cabin pressure monitoring, altitude detection, and fuel tank pressure measurement.• Oil and gas exploration, for example, downhole pressure sensing, reservoir management, drilling operations• Environmental monitoring, for example, oceanography, hydrology, water quality assessment.• Infrastructure monitoring, for example, structural health monitoring (bridges, dams, pipelines), seismic activity detection.• Hydraulic systems, for example, industrial machinery control, fluid pressure monitoring.• Subsea operations, for example, remotely operated vehicles (ROVs), underwater robots.• Manufacturing and quality control, for example, process monitoring, product quality assurance.• Research and Development, for example, material testing, fluid dynamics research.• Key Features & benefits Current invention based on the above embodiments has the following key features and benefits: 1) Dual CFRP-embedded FBGs on opposing sides of the diaphragm mitigate temperature effects and double sensor sensitivity. 2) FBG pressure sensors can be cascaded into arrays for simultaneous pressure measurements at multiple locations. 3) The form factor of the sensor can be customized according to the structure of the subject to be tested. 4) The sensor's physical configuration can be customized to match the structure of the subject under examination, with minimal disruption to surrounding wave profiles.

[0090] The following key features, benefits, and potential impact of the FBG pressure sensor, position it as an innovative solution for a wide range of industries and applications. 1) Enhanced Pressure Sensing: The FBG pressure sensor offers precise and reliable pressure sensing capabilities suitable for a wide range of applications, from aerospace to Hydraulic Systems. 2) Temperature Compensation: The sensor's unique diaphragm structure and dual FBG configuration provide effective temperature compensation, ensuring accurate pressure measurements even in varying temperature environments. 3) Versatility: The sensor's adaptable design allows for customization in terms of materials, dimensions, and sensing technologies, making it versatile for use in different applications and industries. 4) High-Pressure Tolerance: The sensor can withstand high-pressure environments, making it suitable for challenging applications such as oil well monitoring and aerospace pressure sensing. 5) Compact and Thin Design: With a thin profile having thickness 2 mm thick (with < 3 mm overall thickness (typically in a range of 2 to 3 mm), the sensor arrangement 100, 100A minimizes interference with surrounding structures and is suitable for use in compact and confined spaces. 6) Waterproof and Submersible: The sensor arrangement 100, 100A robust construction and waterproof adhesive ensure its suitability for underwater applications, including oceanography and subsea operations. 7) Improved linearity: The sensor arrangement 100, 100A demonstrates excellent linearity, surpassing 99%, which is essential for precise pressure measurements in various industries, including civil engineering and automotive. 8) Customizable shapes: The diaphragm's shape can be tailored to circular, square, or rectangular forms, allowing flexibility in sensor design for specific applications. 9) Structural integrity: The sensor's secure attachment to a 3D printed cavity and reinforcement with epoxy and waterproof adhesive enhance its structural integrity, ensuring long-term reliability. 10) Wide application range: The sensor arrangement 100, 100A finds applications in diverse fields, including aerospace, medical devices, environmental monitoring, automotive, and more, making it a versatile technology with broad utility. It may be appreciable that the high-pressure tolerance may be enabled by the CFRP-embedded FBGs to improve strain transfer and protect the grating; (ii) diaphragm design, including material modulus and thickness may be sized to avoid plastic deformation at target pressures; (iii) a stiff, additive manufacturing (e g.3D-printed base) that limits boundary compliance; and (iv) peripheral sealing that maintains cavity integrity under hydrostatic loads

[0091] In some embodiments, the diaphragm has a thickness of 0.10 mm to 0.50 mm and a Young’s modulus of > 2 gigapascal (GPa), and each FBG is embedded within a 2 to 4-ply CFRP laminate bonded to the diaphragm, the base being additively manufactured with a wall thickness of > 1 mm, thereby conferring a pressure tolerance of at least 20 kiloPascal (kPa) without plastic deformation of the diaphragm. In some embodiments, the 20 kPa threshold matches the basin “slamming” requirement envelope and the 1.9 m water-column lab limit.

[0092] In summary, the present disclosure provides for a pressure sensor arrangement, the pressure sensor arrangement comprising a pair of FBG sensors coupled to a diaphragm, wherein the pair of FBG sensors are arranged in proximity with respect to each other for exposure to similar temperature to achieve temperature compensation. In some embodiments, the pair of FBG sensors are symmetrically disposed on opposing sides of the diaphragm, such that a pressure sensitivity of the pressure sensor having the pair of FBG sensors may be doubled compared to one FBG sensor. In some embodiments, each FBG sensor may be embedded inside a carbon fiber-reinforced polymer (CFRP) prepreg, which is bonded to the diaphragm. In some embodiments, the base structure of the sensor can be 3D-printed, allowing customization for various shapes and sizes depending on the application This is particularly useful in industries where sensor design needs to fit into non-standard or curved surfaces, such as underwater vessels or aircraft structures. The 3D-printed base structure 110A provides flexibility and accelerates the fabrication process, allowing the pressure sensor arrangement to be adaptable for various applications while maintaining structural integrity. The pressure sensor arrangement further includes waterproof sealants applied around the interface between the diaphragm layer and the 3D-printed base. This ensures that water or liquid does not infiltrate the sensor’s internal structure, especially the central air void, which could otherwise affect the sensor's pressure-sensing capabilities. The epoxy and waterproof adhesive used in the construction also help maintain the sensor's performance in submerged or moisture-exposed environments, which is critical for applications like oceanography and subsea operations. These waterproofing measures preserve the accuracy of the sensor when submerged for extended periods. Based on the above key features, the diaphragm structure is capable of deformation when subjected to pressure. In one embodiment, the diaphragm is typically made or formed from materials, such as, but not limited to, PVC or PC sheets, though in this case, it is bonded to CFRP (carbon fiber-reinforced polymer) prepregs for improved mechanicalproperties. The diaphragm’s thin and flexible design ensures minimal interference with surrounding fluid or wave profiles while providing accurate pressure readings.

[0093] To prevent or minimize hysteresis during repetitive testing in water, which affects accuracy, the two-FBG pair configuration in one embodiment may mitigate hysteresis. With FBGs arranged symmetrically, one of the FBG senor may experience tension and the other FBG sensor may experience compression. Such an arrangement balances out the non-linear effects that cause hysteresis. Based on the above key features, a high level of linearity (R-squared value greater than 99%) may be achieved, which is essential for accurate pressure measurement. This improvement is attributed to the CFRP-embedded FBGs, which provide consistent and reliable responses to pressure changes. Pressure sensitivity remains competitive with commercially available sensors (e.g., Luna pslOOO), though with temperature compensation, it surpasses these in long-term stability and performance.

[0094] The pressure sensor arrangement may allow for cascading multiple FBG sensors in arrays for simultaneous pressure measurements across different locations. This makes it versatile for use in applications such as structural health monitoring, fluid dynamics research, and seismic activity detection. The thin profile of the sensor (about 2 mm thick) makes it ideal for confined spaces or where minimal disturbance to the surrounding environment is required (e.g., ship hulls or aircraft surfaces).

[0095] The pressure sensor arrangement may be waterproof and submersible, which broadens its application in marine and subsea environments. The materials used are chemically resistant, ensuring that the sensor can endure exposure to relatively harsh substances such as isopropyl alcohol.

[0096] It may be contemplated that the pressure sensor arrangement comprising opposing-strain dual-FBG on a diaphragm, with CFRP embedding, two-piece 3D-printed base structure, peripheral waterproof seal, and diagonal fiber routing, may improve linearity & mitigate hysteresis; retain system claims for cascaded arrays.

[0097] In some embodiments, the dual-FBG arrangement on opposing sides of the diaphragm may be disposed symmetrically about a neutral plane of the diaphragm such that equal-magnitude, opposite-sign strain is produced under flexure

[0098] In some embodiments, there may comprise a pressure sensor arrangement comprising a diaphragm and a base structure, wherein each of a first and second FBG is pre-embedded within a CFRP prepreg and bonded to opposing sides of the diaphragm, the basebeing a single-piece 3D-printed structure defining a cavity and surrounded by a continuous waterproof seal at the diaphragm-base structure interface, wherein the arrangement exhibits reduced hysteresis relative to bonding bare FBGs directly to the diaphragm.

[0099] In some embodiments, the CFRP may be pre-embedding prior to bonding.

[0100] In some embodiments, the base structure may be a 3D printed single-piece with continuous waterproof sealant.

[0101] In some embodiments, there may comprise an optical fiber path diagonal across two diaphragm comers to equalize strain distribution.

[0102] In some embodiments, the overall thickness of the pressure sensor arrangement may be less than or equal to (<) 3 mm.

[0103] In some embodiments, one or more sensor arrangements may be cascaded along a common fiber; interrogator & processing unit for detection of slamming events.

[0104] While the disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims. The scope of the disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1. A pressure sensor arrangement comprising:a base structure, the base structure defining a cavity;a diaphragm, the diaphragm positioned on the base structure in a manner such as to deform under an applied pressure, the deformation toward or into the cavity;a first Fiber Bragg Grating (FBG) disposed on a first side of the diaphragm, and a second FBG disposed on an opposing second side of the diaphragm relative to a neutral plane of the diaphragm, the first FBG and the second FBG forming an optical fiber sensor;wherein the first FBG and the second FBG are positioned in a manner such that upon the application of the applied pressure, the first FBG and the second FBG experience opposing strain relative to each other.

2. The pressure sensor arrangement of claim 1, wherein upon the application of the applied pressure, the first FBG experiences tensile strain and the second FBG experiences compressive strain.

3. The pressure sensor arrangement of claim 2, wherein at least one of the first FBG and / or the second FBG is embedded within a carbon fiber reinforced polymer (CFRP) prepreg bonded to the diaphragm.

4. The pressure sensor arrangement of any one of the preceding claims, further comprising a waterproof sealant, wherein the waterproof sealant is applied around an interface between the diaphragm and the base structure.

5. The pressure sensor arrangement of any one of the preceding claims, wherein the diaphragm comprises a polymer sheet selected from polycarbonate (PC) or polyvinyl chloride (PVC).

6. The pressure sensor arrangement of any one of the preceding claims, wherein the base structure comprises a base sheet and a hollow frame layered on the base sheet, the hollow frame defining the cavity, and the diaphragm is dimensioned to form a cover over the hollow frame.

7. The pressure sensor arrangement of any one of the preceding claims, wherein the diaphragm is dimensioned to cover the cavity and form a pressure chamber, the diaphragm being configured to deform into the cavity when pressure is applied to a first side of the diaphragm.

8. The pressure sensor arrangement of claim 6, wherein the first FBG and second FBG are directly bonded to the diaphragm using an adhesive layer.

9. The pressure sensor arrangement of claim 8, wherein each of the first FBG and the second FBG is positioned at or near a central region of the diaphragm.

10. The pressure sensor arrangement of claim 9, wherein the adhesive layer is disposed between each of the first FBG, the second FBG, and the diaphragm; and wherein a protective epoxy layer covers at least a grating region of each of the first FBG and the second FBG.

11. The pressure sensor arrangement of any one of the preceding claims, wherein the first FBG has a first Bragg wavelength and the second FBG has a second Bragg wavelength different from the first Bragg wavelength.

12. The pressure sensor arrangement of claim 11, wherein the first Bragg wavelength is a shorter wavelength than the second Bragg wavelength.

13. A method of manufacturing a pressure sensor arrangement, the method comprising: forming a base structure;defining a cavity on the base structure;providing a flexible sheet configured as a diaphragm;positioning the diaphragm on the base structure in a manner such as to deform under an applied pressure, the deformation toward or into the cavity; anddisposing a first Fiber Bragg Grating (FBG) disposed on a first side of the diaphragm, and a second FBG on an opposing second side of the diaphragm relative to a neutral plane of the diaphragm, the first FBG and the second FBG forming an optical fiber sensor;wherein upon the application of the applied pressure, the first FBG and the second FBG experience opposing strain relative to each other.

14. The method of claim 13, further comprising securing the first FBG and the second FBG to the diaphragm, using an adhesive.

15. The method of claim 13 or 14, wherein defining the cavity on the base structure further comprises forming a hollow frame defining the cavity, bonding the diaphragm to the hollow frame using a waterproof adhesive so as to cover the cavity; and applying a waterproof sealing layer over at least part of a grating region defined by the first FBG and the second FBG.

16. The method of claim 15, wherein the base structure, the hollow frame, and the diaphragm are substantially square.

17. The method of claim 16, wherein the base structure has dimensions of approximately 28 millimetres (mm) x 28 mm and a thickness of approximately 0.4 mm; the hollow frame has outer dimensions of approximately 28 mm x 28 mm and inner dimensions of approximately 20 mm x 20 mm with a thickness of approximately 0.4 mm, and the diaphragm has dimensions of approximately 28 mm x 28 mm and a thickness of approximately 0.2 mm.

18. A slamming event monitoring system for a marine vessel, comprising:at least one pressure sensor arrangement of any one of claims 1 to 11, the at least one pressure sensor arrangement mounted at a bow region of the marine vessel;an optical interrogator operatively connected to the at least one pressure sensor arrangement to receive wavelength shift signals from the first FBG and the second FBG; anda processing unit configured to: determine pressure data from the wavelength shift signals; and detect one or more slamming events based on the pressure data.

19. The slamming event monitoring system of claim 18, wherein the processing unit is further configured to: record pressure data over a time period, establish one or more loading profiles based on the recorded pressure data; predict structural fatigue life of the marine vessel basedon the loading profiles; and trigger a warning signal when one or more slamming events or a predetermined loading condition is detected.

20. The slamming event monitoring system of claim 18 or 19, wherein a plurality of the pressure sensor arrangement are optically cascaded along a common optical fiber to form a pressure sensor array; the optical interrogator is configured to interrogate the pressure sensor array; and the processing unit is configured to: determine spatially distributed pressure data at a plurality of locations along the bow region, and detect one or more slamming events based on the spatial pressure distribution.

21. The pressure sensor arrangement of any one of claims 1 to 12, wherein the diaphragm comprises a thickness in a range of 0.10 mm to 0.50 mm, and a Young’s modulus of more than or equal to 2 Gigapascal (GPa), and each FBG is embedded within a 2 to 4-ply CFRP laminate bonded to the diaphragm, the base structure being additively manufactured with a wall thickness of more than or equal to 1 mm.

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