Optical fiber array film sensor and multi-dimensional force detection method

Abstract

The application discloses a fiber array film sensor and a multi-dimensional force detection method, which comprises a flexible top layer, column electrodes, row electrodes, a flexible bottom layer and a composite piezoresistive film; the column electrodes are printed on the flexible top layer, the row electrodes are printed on the flexible bottom layer, and the composite piezoresistive film is arranged between the column electrodes and the row electrodes; the composite piezoresistive film is a composite film formed by embedding row optical fibers and column optical fibers in the piezoresistive film; the row optical fibers and the column optical fibers each have an input end and an output end; the intersection points of the optical fibers of the fiber array and the intersection points of the piezoresistive array are partially overlapped, and the covered area of the fiber array is overlapped with the covered area of the piezoresistive array; the input end of the row optical fiber is connected to the optical fiber of an OFDR strain sensor and the light source optical fiber of a micro-bending sensor through a coupler, and the output end of the row optical fiber is coupled to a micro-bending photodetector of the micro-bending sensor; and the input end of the column optical fiber is also coupled to the optical fiber of the OFDR strain sensor. The vertical pressure and the horizontal tensile force can be simultaneously measured.

Description

Technical Field

[0001] This invention relates to the field of flexible electronics technology, and more particularly to sensor technology, microelectronics technology, and robot tactile sensing technology, specifically to a fiber optic array thin-film sensor and a multi-dimensional force detection method. Background Technology

[0002] In recent years, breathing and heart rate monitoring mattresses and anti-bedsore sensor mattresses have received increasing attention and application as part of the field of intelligent health monitoring. These mattresses utilize built-in sensors and technology to non-invasively monitor a person's breathing, heart rate, and bed pressure distribution, providing users with health data and sleep quality analysis, effectively preventing bedsores. Breathing and heart rate monitoring mattresses and anti-bedsore sensor mattresses are particularly suitable for elderly care and long-term care environments, allowing caregivers to promptly identify and address common health problems in the elderly population, such as cardiovascular disease, sleep apnea, and the risk of bedsores.

[0003] BCG (cardiac impact) signals are tiny vibrations in the human body caused by the heartbeat and the impact and flow of blood in the large arteries, collected through physical or electrical means. They reflect the mechanical properties and kinematic characteristics of the heart. BCG signals can be collected without restraint or even contact, and contain a wealth of cardiac information, providing a non-invasive method of cardiac monitoring.

[0004] BCG signals are generated from a complex physiological process, exhibiting not only multidirectional characteristics but also varying signal intensity and spectrum in different directions. Human respiratory movements and sudden body movements during prolonged experiments directly affect the acquired BCG signals. During respiration, the rib cage generates tension in both vertical and horizontal directions. The upward tension causes rib cage expansion, while the downward tension acts entirely on the mattress. Horizontally, the rib cage generates tension in multiple directions, and these forces generally cancel each other out, preventing the mattress from being significantly affected by respiratory forces in any single direction. Therefore, performing BCG detection horizontally while in a supine position effectively removes most of the influence of respiratory movements; thus, the direction parallel to the spine is the optimal direction for BCG signal acquisition during sleep.

[0005] Anti-decubitus ulcer sensing mattresses typically use array-type tactile sensors to detect external contact. These array-type tactile sensors are thin-film sensors composed of multiple tactile sensing units. Traditional array-type tactile sensors have drawbacks such as difficulty in calibration, poor anti-interference capabilities, and inability to measure lateral pressure. Temperature and humidity changes, as well as high-frequency signals, can affect their performance and accuracy, requiring additional calibration and maintenance to ensure long-term stability and accuracy. Breathing and heart rate monitoring mattresses typically use capacitive and piezoresistive sensors to detect pressure perpendicular to the detection surface. These sensors generally cannot distinguish changes in horizontal tension, making it difficult to achieve simultaneous and accurate measurement of breathing and BCG signals. For example, document CN109990927A discloses a double-layer capacitive flexible tactile sensor and its fabrication method. This double-layer capacitive sensor consists of an upper electrode layer, a lower electrode layer, and an ion-fiber layer disposed between the upper and lower electrode layers, but it cannot achieve multi-dimensional force measurement or accurate measurement of vertical pressure. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a fiber optic array thin-film sensor and a multi-dimensional force detection method, thereby solving the problem mentioned in the background that existing array thin-film sensors cannot simultaneously measure vertical pressure and lateral tension, and require recalibration in the face of different interferences.

[0007] The technical solution of the present invention to solve the technical problem of the identification method is as follows:

[0008] In a first aspect, the present invention provides a fiber optic array thin-film sensor capable of simultaneously measuring vertical pressure and lateral tension. The fiber optic array thin-film sensor includes a flexible top layer 1, column electrodes 2, row electrodes 3, a flexible bottom layer 4, and a composite piezoresistive film 5. The column electrodes 2 are printed on the flexible top layer 1, and the row electrodes 3 are printed on the flexible bottom layer 4. The composite piezoresistive film 5 is located between the column electrodes 2 and the row electrodes 3.

[0009] The composite piezoresistive film 5 is a composite film formed by embedding row optical fibers 502 and column optical fibers 503 within a piezoresistive film 501. In the entire composite piezoresistive film, the row optical fiber is a whole optical fiber forming a row along a serpentine path, and the column optical fiber is a whole optical fiber forming a column along a serpentine path. The a row and b columns are perpendicular to each other to form a×b optical fiber intersection points, which constitute an optical fiber array. Both the row optical fiber and the column optical fiber have an input end and an output end.

[0010] The column electrode 2, row electrode 3 and piezoresistive film 501 form an array-type piezoresistive film sensor, wherein the m row electrodes and n column electrodes intersect each other perpendicularly to form m×n piezoresistive array intersection points, thus forming a piezoresistive array;

[0011] The fiber intersections of the fiber array and the piezoresistive array partially coincide, the area covered by the fiber array and the area covered by the piezoresistive array coincide, and the resolution of the fiber array is smaller than that of the piezoresistive array.

[0012] The input end of the row optical fiber 502 is simultaneously connected to the optical fiber of the OFDR strain sensor and the light source optical fiber of the microbending sensor through a coupler. In addition, the output end of the row optical fiber 502 is coupled to the microbending photodetector of the microbending sensor.

[0013] The input end of the column fiber 503 is also simultaneously coupled to the fiber of the OFDR strain sensor.

[0014] Furthermore, the coupler is a three-terminal coupler that couples the fiber input end of the optical fiber, the optical fiber of the OFDR strain sensor, and the light source optical fiber of the microbending sensor together; the flexible top layer and the flexible bottom layer are both made of at least one of PU film, TPU, and PI.

[0015] Secondly, the present invention provides a method for fabricating the aforementioned fiber array thin-film sensor, wherein the fabrication method comprises:

[0016] Step 1: Preparation of composite piezoresistive film: First, fix two whole optical fibers in row a and column b on the coating platform of the coating machine. Row a is the row fiber and column b is the column fiber. The row and column fibers intersect to form a×b fiber intersections. Place the piezoresistive film slurry and start the coating machine to coat it, so that the piezoresistive film slurry completely covers all fiber intersections formed by the row and column fibers. After the piezoresistive film slurry forms a film, flip it over and repeat the coating process until the piezoresistive film slurry completely covers the row and column fibers. Wait for the piezoresistive film slurry to form a film again, forming a composite piezoresistive film with a piezoresistive film embedded in the fiber array on both sides.

[0017] Step 2: The column electrodes and row electrodes are both made by screen printing conductive silver paste onto a flexible material to form stretchable flexible electrodes, thus obtaining a flexible bottom layer with printed row electrodes and a flexible top layer with printed column electrodes.

[0018] Step 3, Packaging:

[0019] The flexible top layer with printed column electrodes, the composite piezoresistive film, and the flexible bottom layer with printed row electrodes are encapsulated together from top to bottom in a sandwich structure. The row electrodes and column electrodes intersect each other perpendicularly to form m×n intersection points of the piezoresistive array, and the input and output ends of the row and column optical fibers, as well as the electrode input and output ports of the piezoresistive array, are reserved.

[0020] Thirdly, this invention provides a multidimensional force detection method, which utilizes the aforementioned fiber array thin-film sensor. The array-type piezoresistive thin-film sensor is connected to an embedded microcontroller. The input ends of the row optical fibers and column optical fibers are connected to an OFDR strain sensor. Simultaneously, the input and output ends of the row optical fibers are connected to the light source fiber and the microbending photodetector of a microbending sensor, respectively. A host computer is electrically connected to both the embedded microcontroller and the OFDR controller. The OFDR controller is connected to the OFDR strain sensor, and the microbending sensor is electrically connected to the embedded microcontroller. The embedded controller transmits the detection data from the microbending sensor and the data detected by the array-type piezoresistive thin-film sensor to the host computer. The specific detection process is as follows:

[0021] Part 1: Z-axis pressure detection

[0022] Start the host computer and embedded microcontroller, and set the sampling frequency of the embedded microcontroller and the data storage mode of the host computer to continuous storage; apply the z-axis pressure feature to the array-type piezoresistive thin-film sensor, and each frame of its output signal contains m×n z-axis relative pressure data, which constitute the z-axis relative pressure matrix F. rp Simultaneously, each frame of the micro-bend sensor's output signal contains one z-axis pressure data point, which is the sum of the absolute z-axis pressure values ​​F experienced at each fiber optic intersection of the micro-bend sensor. ww ;

[0023] Part Two: Calculation of Absolute Pressure along the Z-Axis

[0024] A z-axis pressure feature is applied to a fiber array thin-film sensor. The pressure area of ​​the z-axis pressure feature is larger than the resolution of the micro-bending sensor. All fiber intersections on the fiber array covered by the pressure area of ​​the z-axis pressure feature are obtained. Then, the piezoresistive array intersection that coincides with all fiber intersections covered by the pressure area is found. The relative pressure F at this piezoresistive array intersection, which coincides with all fiber intersections covered by the pressure area, is obtained using an array-type piezoresistive thin-film sensor. rp (c,d), the absolute pressure value F along the z-axis at each intersection of the piezoresistive array of the entire array-type piezoresistive thin-film sensor is obtained according to the following formula. abs (k, l) represents the absolute pressure distribution along the z-axis;

[0025]

[0026] Where C and D are the number of rows and columns of the piezoresistive array intersection points that coincide with the fiber intersection points within the pressure area of ​​the z-axis pressure feature, respectively, 1≤c≤C≤m, 1≤d≤D≤n; 1≤k≤m, 1≤l≤n, and (k,l) represents any piezoresistive array intersection point in the piezoresistive array.

[0027] Part Three: X-axis and Y-axis Tension Testing

[0028] Start the host computer and OFDR controller, and set the sampling frequency of the OFDR controller according to the length of the row and column optical fibers. Set the data storage mode of the host computer to continuous storage. Apply the x-axis strain characteristic to the fiber array thin film sensor. Each frame of the OFDR strain sensor output signal contains 'a' x-axis strain data. The x-axis strain array is an array formed by the x-axis strain values ​​of each row of the OFDR strain sensor, thereby obtaining the x-axis tension. Apply the y-axis strain characteristic to the fiber array thin film sensor. Each frame of the OFDR strain sensor output signal contains 'b' y-axis strain data. The y-axis strain array is an array formed by the y-axis strain values ​​of each row of the OFDR strain sensor, thereby obtaining the y-axis tension.

[0029] Furthermore, the embedded microcontroller can be implemented using an STM32 microcontroller.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The multidimensional force detection method of this invention combines three measuring sensor devices. The relative pressure value of the z-axis is obtained through an array-type piezoresistive thin film sensor. The sum of the absolute pressure values ​​of the z-axis is measured through a micro-bend sensor formed by the cross intersection of row and column optical fibers. The sum of the absolute pressure values ​​of the z-axis is discretized by an algorithm to obtain the absolute pressure distribution of the z-axis at the level of the piezoresistive array, which improves the measurement accuracy of the z-axis pressure value. At the same time, the x-axis and y-axis strain values ​​are measured by connecting to an OFDR strain sensor through row and column optical fibers. There is no need to recalibrate when changing the measurement direction, and the x-axis and y-axis tensile values ​​can be obtained directly, realizing multidimensional force array detection of thin film sensors.

[0032] 2. In this invention, the fiber array thin film sensor has an OFDR strain sensor fiber and a microbending sensor fiber coupled at the row fiber input end. The OFDR strain sensor and the microbending sensor scan and work through the same working fiber (row fiber), which facilitates fiber optic cabling and reduces the difficulty of quantitative analysis of microbending sensing.

[0033] 3. This invention employs a fiber optic array thin-film sensor for multidimensional force detection, offering advantages such as excellent flexibility, high sensitivity, high reliability, large measuring range, and low cost. At certain locations on the piezoresistive array where the intersection of the fiber optic objects is located, fiber optic detection allows it to be assumed that the array's capacitance and resistance are subjected to essentially the same interference, eliminating the need for repeated calibration and simplifying the detection process. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall structure of the fiber array thin film sensor and multidimensional force detection method of the present invention;

[0035] Figure 2 For the present invention Figure 1 A schematic diagram of the structure and spatial coordinates of the composite piezoresistive film 5;

[0036] Figure 3 This is a schematic diagram showing the connection and coupling between the row and column optical fibers and the microbending sensor and OFDR strain sensor in the fiber array thin film sensor of the present invention;

[0037] Figure 4 This is a schematic diagram illustrating the detection principle of the OFDR strain sensor in the invention.

[0038] Figure 5 This is a schematic diagram illustrating the detection principle of the micro-bending sensor in the invention.

[0039] Figure 6 This is a schematic diagram of pressure discretization for the invention of a multidimensional force detection method.

[0040] In the figure: 1. Top layer PU, 2. Column electrode, 3. Row electrode, 4. Bottom layer PU, 5. Composite piezoresistive film, 501 piezoresistive film, 502. Row optical fiber, 503. Column optical fiber. Detailed Implementation

[0041] Specific embodiments of the present invention are given below. These specific embodiments are only used to further illustrate the present invention in detail and do not limit the scope of protection of the claims of the present invention.

[0042] This invention provides a fiber optic array thin-film sensor capable of simultaneously measuring vertical pressure and lateral tensile force without requiring recalibration during the measurement process, thus enabling multi-dimensional force detection. The fiber optic array thin-film sensor comprises a top PU layer 1, column electrodes 2, row electrodes 3, a bottom PU layer 4, and a composite piezoresistive film 5; the column electrodes 2 are printed on the top PU layer 1, and the row electrodes 3 are printed on the bottom PU layer 4; the composite piezoresistive film 5 is located between the column electrodes 2 and the row electrodes 3.

[0043] The composite piezoresistive film 5 is a composite film formed by embedding row optical fibers 502 and column optical fibers 503 within a piezoresistive film 501. In the entire composite piezoresistive film, the row optical fiber is a whole optical fiber forming a row along a serpentine path, and the column optical fiber is a whole optical fiber forming a column along a serpentine path. The a row and b columns are perpendicular to each other to form a×b optical fiber intersection points, which constitute an optical fiber array. Both the row optical fiber and the column optical fiber have an input end and an output end. The piezoresistive film 501 operates on the principle of piezoresistive. The column electrode 2, the row electrode 3, and the piezoresistive film 501 form an array-type piezoresistive film sensor, wherein the m row electrodes and n column electrodes are perpendicular to each other to form m×n piezoresistive array intersection points, which form a piezoresistive array.

[0044] The fiber intersections of the fiber array and the piezoresistive array partially coincide, the area covered by the fiber array and the area covered by the piezoresistive array coincide, and the resolution of the fiber array is smaller than that of the piezoresistive array.

[0045] The input end of the row optical fiber 502 is simultaneously connected to the optical fiber of the OFDR strain sensor and the light source optical fiber of the microbending sensor via a coupler. In addition, the output end of the row optical fiber 502 is coupled to the microbending photodetector of the microbending sensor. The microbending sensor is not sensitive to strain and can only detect bending degrees close to the fiber radius.

[0046] The coupler is a three-terminal coupler that couples the fiber optic input end, the fiber optic cable of the OFDR strain sensor, and the light source fiber optic cable of the microbending sensor together.

[0047] The input end of the column fiber 503 is also coupled to the fiber of the OFDR strain sensor. The OFDR strain sensor is connected to both the row fiber and the column fiber, enabling simultaneous demodulation of the row and column.

[0048] The row fiber 502, column fiber 503 and OFDR (Optical Frequency Domain Reflection) strain sensor can use the OFDR principle to monitor strain in the xy direction, realizing effective decoupling of pressure and strain of piezoresistive thin film sensor. The fiber intersection between the row fiber 502 and column fiber 503 combined with the microbending sensor can perform high-precision detection of the absolute pressure distribution of the z-axis of the piezoresistive array based on the microbending principle.

[0049] The fabrication process of the fiber optic array thin-film sensor is as follows:

[0050] Step 1: Composite Piezoresistive Film Preparation Process: First, fix two whole optical fibers in row a and column b on the coating platform of the coating machine. Row a is the row fiber, and column b is the column fiber. The row and column fibers intersect to form a×b fiber intersection points. Place the piezoresistive film slurry and start the coating machine to coat it, ensuring that the piezoresistive film slurry completely covers all fiber intersection points formed by the row and column fibers. Wait for the piezoresistive film slurry to form a film, peel off the piezoresistive film (at this time, the row and column fibers are fixed on one side of the piezoresistive film), flip it over, and repeat the coating process until the piezoresistive film slurry completely covers the row and column fibers. Wait for the piezoresistive film slurry to form a film, forming a composite piezoresistive film with a double-sided piezoresistive film-embedded fiber array.

[0051] Step 2: The preparation of column electrodes and row electrodes involves forming stretchable flexible electrodes by screen printing conductive silver paste onto a PU film, resulting in a bottom PU layer with printed row electrodes and a top PU layer with printed column electrodes. Specifically, the screen is placed on the PU film, silver paste is placed on one side of the screen, and the silver paste is applied by scraping with a squeegee. This process is repeated several times until the paste is evenly applied to the screen. The screen is then removed, and the PU film is left to dry until the silver paste dries.

[0052] Step 3, Packaging:

[0053] The top layer of PU with printed column electrodes, the composite piezoresistive film, and the bottom layer of PU with printed row electrodes are encapsulated together in a sandwich structure from top to bottom. The row and column electrodes intersect perpendicularly to each other, forming m×n intersection points of the piezoresistive array. The input and output ends of each row and column optical fiber, as well as the electrode input and output ports of the piezoresistive array, are reserved. During encapsulation, the bent parts of the optical fiber can also be encapsulated as a whole.

[0054] The fiber array thin-film sensor provided by this invention encapsulates a fiber array and a piezoresistive array within a single thin film. The array-type piezoresistive thin-film sensor is connected to an embedded microcontroller. The input ends of the row and column fibers are connected to OFDR (Optical Frequency Domain Reflectometry) strain sensors. Simultaneously, the input and output ends of the row fibers are connected to the light source fiber and micro-bend photodetector of a micro-bend sensor, respectively. By combining these three measurement sensor devices, a host computer is electrically connected to both the embedded microcontroller and the OFDR controller. The OFDR controller is connected to the OFDR strain sensor, and the micro-bend sensor is electrically connected to the embedded microcontroller. Combining the micro-bend sensor and the array-type piezoresistive thin-film sensor solves the problem of repeated calibration caused by environmental noise interference in the array-type piezoresistive thin-film sensor. It also achieves higher spatial resolution than existing fiber optic sensors. The OFDR strain sensor enables individual strain detection, solving the problem of difficult decoupling of pressure and strain in piezoresistive thin-film sensors.

[0055] OFDR is a distributed optical fiber measurement technology based on the principle of optical frequency-modulated continuous wave. It uses the Fourier transform relationship between the frequency of the swept-frequency optical interference signal and the position of the optical fiber to obtain characteristic information such as scattering / reflection / loss, phase and polarization distributed along the optical fiber. It can further invert the distribution of external physical fields such as strain sensed by the optical fiber.

[0056] OFDR utilizes a narrowband laser and an acousto-optic modulator to generate a swept-frequency optical signal. The optical signal is split into two paths by a coupler. One path enters the detection fiber, where Rayleigh scattering occurs, causing the light to return along the original path. The other path enters the reference fiber, passes a tail mirror, and returns along the same path. The two backscattered beams are coupled by an fiber coupler and enter a photodetector. The two beams satisfy the coherence condition and undergo coherent mixing. The photodetector then converts the optical signal into an electrical signal (see [link]). Figure 4 ).

[0057] Microbend sensors are a type of fiber optic measurement technology based on the principle of light intensity modulation. They utilize physical fields to transmit force to optical fibers through deformers, causing microbends and deformations. The deformation of the optical fiber leads to an increase or decrease in the radiation of the radiation mode, thereby achieving modulation of the optical carrier intensity. This allows for the further inversion of the distribution of external physical fields such as temperature and strain sensed by the optical fiber.

[0058] The microbending sensor (including a photodetector, filter, and acquisition unit) generates an optical signal from its microbending light source, which enters the detection optical fiber (i.e., the row fiber). When the detection fiber undergoes microbending and deformation, the optical signal passing through the fiber causes microbending loss, which is then converted into an electrical signal by the microbending photodetector. In this embodiment, the microbending sensor is connected to an embedded controller, which transmits the detection data from the microbending sensor and the data detected by the arrayed piezoresistive thin-film sensor to a host computer.

[0059] The specific process for performing multidimensional force detection is as follows:

[0060] Part 1: Z-axis pressure detection

[0061] Start the host computer and embedded microcontroller, and set the sampling frequency of the embedded microcontroller and the data storage mode of the host computer to continuous storage; apply the z-axis pressure feature to the array-type piezoresistive thin-film sensor, and each frame of its output signal contains m×n z-axis relative pressure data, which constitute the z-axis relative pressure matrix F. rp The z-axis relative pressure matrix is ​​a matrix formed by the z-axis relative pressure values ​​at the intersections of the piezoresistive arrays of each row and column of the arrayed piezoresistive thin-film sensor. Simultaneously, each frame of the micro-bend sensor's output signal contains one z-axis pressure data point, which is the sum of the absolute z-axis pressure values ​​F experienced at each fiber intersection of the micro-bend sensor. ww ;

[0062] Part Two: Calculation of Absolute Pressure along the Z-Axis

[0063] A z-axis pressure feature is applied to a fiber array thin-film sensor. The pressure area of ​​the z-axis pressure feature is larger than the resolution of the micro-bending sensor. All fiber intersections on the fiber array covered by the pressure area of ​​the z-axis pressure feature are obtained. Then, the piezoresistive array intersection that coincides with all fiber intersections covered by the pressure area is found. The relative pressure F at this piezoresistive array intersection, which coincides with all fiber intersections covered by the pressure area, is obtained using an array-type piezoresistive thin-film sensor. rp (c,d), the absolute pressure value F along the z-axis at each intersection of the piezoresistive array of the entire array-type piezoresistive thin-film sensor is obtained according to the following formula. abs (k, l) represents the absolute pressure distribution along the z-axis;

[0064]

[0065] Where C and D are the number of rows and columns of the piezoresistive array intersection points that coincide with the fiber intersection points within the pressure area of ​​the z-axis pressure feature, respectively, 1≤c≤C≤m, 1≤d≤D≤n; 1≤k≤m, 1≤l≤n, and (k,l) represents any piezoresistive array intersection point in the piezoresistive array.

[0066] Part Three: X-axis and Y-axis Tension Testing

[0067] Start the host computer and OFDR controller, and set the sampling frequency of the OFDR controller according to the length of the row and column optical fibers. Within the range supported by the OFDR device, it can be equal to or different from the frequency setting in the first part. Set the data storage mode of the host computer to continuous storage. Apply the x-axis strain characteristic to the fiber array thin film sensor. Each frame of the OFDR strain sensor output signal contains a x-axis strain data. The x-axis strain array is an array formed by the x-axis strain values ​​of each row of the OFDR strain sensor. Apply the y-axis strain characteristic to the fiber array thin film sensor. Each frame of the OFDR strain sensor output signal contains b y-axis strain data. The y-axis strain array is an array formed by the y-axis strain values ​​of each row of the OFDR strain sensor.

[0068] In this invention, the embedded microcontroller detects in real time the relative distributed pressure value along the z-axis at the intersection of each row and column of the piezoresistive thin-film sensor and the sum of the absolute pressure values ​​along the z-axis at the intersection of each row and column of the fiber optic cable in the microbending sensor, F. ww The absolute z-axis distributed pressure value is then calculated in the embedded microcontroller; in addition, the OFDR controller monitors the strain value Δl of each row and column of the OFDR strain sensor in real time. x，y The calculated tensile force values ​​F along the x-axis and y-axis are... x，y And transmit it to the host computer for display.

[0069]

[0070] Where E is the Young's modulus of the optical fiber, A is the cross-sectional area of ​​the optical fiber, and l x，y This represents the length of the optical fiber.

[0071] by Figure 6 For example, the fiber array thin film sensor includes row fiber p-1, p, p+1, column fiber q-1, q, q+1, row electrodes i-2, i-1, i, i+1, i+2, and column electrodes j-2, j-1, j, j+1, j+2. The fiber array is 3×3, and the piezoresistive array is 5×5. The row electrodes i-2, i, i+2 coincide with the row fibers p-1, p, p+1, and the column electrodes j-2, j, j+2 coincide with the column fibers q-1, q, q+1. Figure 6The z-axis pressure characteristic is applied to the fiber array thin-film sensor. The pressure area is the triangular region enclosed by the thick black solid line. This pressure area acts on only two fiber intersections in the fiber array, namely (p+1, q) and (p, q). The host computer obtains the sum of the absolute z-axis pressure values ​​F of the micro-bend sensor at all row and column fiber intersections covered by the pressure area. ww F ww It can be represented as:

[0072] F ww =F abs (p+1, q)+F abs (p, q)

[0073] Among them, F abs (p+1, q), F abs (p, q) are the absolute pressure values ​​of the z-axis at the corresponding fiber optic intersections. The micro-bend sensor only outputs the sum of the absolute pressure values ​​and does not output the absolute pressure values ​​of each fiber optic intersection.

[0074] Z-axis pressure discretization is performed. When the z-axis pressure feature applies pressure to the fiber array thin film sensor, the pressure area of ​​the z-axis pressure feature is greater than the resolution of the micro-bend sensor, that is, the pressure area acts on at least one fiber intersection.

[0075] The pressure area of ​​the aforementioned triangular region acts on the array-type piezoresistive thin-film sensor. The host computer obtains the denoised z-axis relative pressure value of each sensing unit (piezoresistive array intersection) of the array-type piezoresistive thin-film sensor, and determines whether the pressure value on the piezoresistive array corresponding to the two fiber intersections is 0. If the pressure value is greater than 0, the corresponding piezoresistive array intersection with the fiber intersection covered by the pressure area is found, which is (i+2, j) and (i, j). Although the pressure value at (i+1, j) is greater than 0, it does not coincide with the two fiber intersections mentioned above. Therefore, (i+1, j) is not considered. Only the z-axis relative distributed pressure Frp(i+2, j) and Frp(i, j) corresponding to (i+2, j) and (i, j) are considered. This value is read from the array-type piezoresistive thin-film sensor.

[0076] The sum of the absolute pressure values ​​along the z-axis at all fiber optic intersections within the pressure area covered by the microbend sensor, F ww The absolute pressure F along the z-axis at the intersection points (i+2, j) and (i, j) of the piezoresistive array is obtained by discretization according to the following formula. abs (i+2, j), F abs (i, j).

[0077]

[0078]

[0079] Among them, Frp (c,d) represents the z-axis relative pressure value of the region with pressure greater than 0 in the array-type piezoresistive thin film sensor. C and D are the number of rows and columns of the piezoresistive array intersection points that coincide with the fiber intersection points in the region, respectively. 1≤c≤C≤m, 1≤d≤D≤n.

[0080] This allows us to obtain the absolute pressure value F along the z-axis of each sensing unit in the entire array-type piezoresistive thin-film sensor. abs (k, l).

[0081]

[0082] Among them, F rp (k,l) represents the z-axis relative pressure value at any intersection of the piezoresistive array in the array-type piezoresistive thin film sensor, 1≤k≤m, 1≤l≤n.

[0083] In this application, a and b are both natural numbers greater than 1, and the values ​​of a and b are not less than the corresponding values ​​of m and n.

[0084] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A fiber optic array thin-film sensor, characterized in that, This fiber array thin-film sensor, capable of simultaneously measuring vertical pressure and lateral tension, comprises a flexible top layer, column electrodes, row electrodes, a flexible bottom layer, and a composite piezoresistive film; the column electrodes are printed on the flexible top layer, and the row electrodes are printed on the flexible bottom layer; the composite piezoresistive film is located between the column electrodes and the row electrodes. The composite piezoresistive film is a composite film formed by embedding row optical fibers and column optical fibers within a piezoresistive film. In the entire composite piezoresistive film, the row optical fiber is a whole optical fiber forming a row along a serpentine path, and the column optical fiber is a whole optical fiber forming a column along a serpentine path. The a row and b columns are perpendicular to each other, forming a×b optical fiber intersection points, which constitute an optical fiber array. Both the row optical fiber and the column optical fiber have an input end and an output end. The column electrodes, row electrodes, and piezoresistive thin film form an array-type piezoresistive thin film sensor, wherein the m row electrodes and n column electrodes intersect each other perpendicularly to form m×n piezoresistive array intersection points, thus forming a piezoresistive array; The fiber intersections of the fiber array and the piezoresistive array partially coincide, the area covered by the fiber array and the area covered by the piezoresistive array coincide, and the resolution of the fiber array is smaller than that of the piezoresistive array. The input end of the row fiber is simultaneously connected to the fiber of the OFDR strain sensor and the light source fiber of the microbending sensor via a coupler. The output end of the row fiber is coupled to the microbending photodetector of the microbending sensor. The input end of the optical fiber is also simultaneously coupled to the optical fiber of the OFDR strain sensor.

2. The fiber array thin-film sensor according to claim 1, characterized in that, The coupler is a three-terminal coupler that couples the fiber input end of the optical fiber, the optical fiber of the OFDR strain sensor, and the light source optical fiber of the microbending sensor together; the flexible top layer and the flexible bottom layer are both made of at least one of PU film, TPU, and PI.

3. A method for fabricating the fiber optic array thin-film sensor according to claim 1, characterized in that, The preparation method is as follows: Step 1: Preparation of composite piezoresistive film: First, fix two whole optical fibers in row a and column b on the coating platform of the coating machine. Row a is the row fiber and column b is the column fiber. The row and column fibers intersect to form a×b fiber intersections. Place the piezoresistive film slurry and start the coating machine to coat it, so that the piezoresistive film slurry completely covers all fiber intersections formed by the row and column fibers. After the piezoresistive film slurry forms a film, flip it over and repeat the coating process until the piezoresistive film slurry completely covers the row and column fibers. Wait for the piezoresistive film slurry to form a film again, forming a composite piezoresistive film with a piezoresistive film embedded in the fiber array on both sides. Step 2: The column electrodes and row electrodes are both made by screen printing conductive silver paste onto a flexible material to form stretchable flexible electrodes, thus obtaining a flexible bottom layer with printed row electrodes and a flexible top layer with printed column electrodes. Step 3, Packaging: The flexible top layer with printed column electrodes, the composite piezoresistive film, and the flexible bottom layer with printed row electrodes are encapsulated together from top to bottom in a sandwich structure. The row electrodes and column electrodes intersect each other perpendicularly to form m×n intersection points of the piezoresistive array, and the input and output ends of the row and column optical fibers, as well as the electrode input and output ports of the piezoresistive array, are reserved.

4. A multidimensional force detection method, characterized in that, The detection method utilizes the fiber array thin-film sensor described in claim 1. The array-type piezoresistive thin-film sensor is connected to an embedded microcontroller. The input ends of the row fibers and column fibers are connected to OFDR strain sensors. Simultaneously, the input and output ends of the row fibers are connected to the light source fiber and the microbending photodetector of the microbending sensor, respectively. The host computer is electrically connected to both the embedded microcontroller and the OFDR controller. The OFDR controller is connected to the OFDR strain sensor, and the microbending sensor is electrically connected to the embedded microcontroller. The embedded microcontroller transmits the detection data from the microbending sensor and the data detected by the array-type piezoresistive thin-film sensor to the host computer. The specific detection process is as follows: Part 1: Z-axis pressure detection Start the host computer and embedded microcontroller, and set the sampling frequency of the embedded microcontroller and the data storage mode of the host computer to continuous storage; apply the z-axis pressure feature to the array-type piezoresistive thin-film sensor, and each frame of its output signal contains m×n z-axis relative pressure data, which constitute the z-axis relative pressure matrix F. rp Simultaneously, each frame of the micro-bend sensor's output signal contains one z-axis pressure data point, which is the sum of the absolute z-axis pressure values ​​F experienced at each fiber optic intersection of the micro-bend sensor. ww ; Part Two: Calculation of Absolute Pressure along the Z-Axis A z-axis pressure feature is applied to a fiber array thin-film sensor. The pressure area of ​​the z-axis pressure feature is larger than the resolution of the micro-bending sensor. All fiber intersections on the fiber array covered by the pressure area of ​​the z-axis pressure feature are obtained. Then, the piezoresistive array intersection that coincides with all fiber intersections covered by the pressure area is found. The relative pressure F at this piezoresistive array intersection, which coincides with all fiber intersections covered by the pressure area, is obtained using an array-type piezoresistive thin-film sensor. rp (c,d), the absolute pressure value F along the z-axis at each intersection of the piezoresistive array of the entire array-type piezoresistive thin-film sensor is obtained according to the following formula. abs (k, l) represents the absolute pressure distribution along the z-axis; Where C and D are the number of rows and columns of the piezoresistive array intersection points that coincide with the fiber intersection points within the pressure area of ​​the z-axis pressure feature, respectively, 1≤c≤C≤m, 1≤d≤D≤n; 1≤k≤m, 1≤l≤n, and (k,l) represents any piezoresistive array intersection point in the piezoresistive array. Part Three: X-axis and Y-axis Tension Testing Start the host computer and OFDR controller, and set the sampling frequency of the OFDR controller according to the length of the row and column optical fibers. Set the data storage mode of the host computer to continuous storage. Apply the x-axis strain characteristic to the fiber array thin film sensor. Each frame of the OFDR strain sensor output signal contains 'a' x-axis strain data. The x-axis strain array is an array formed by the x-axis strain values ​​of each row of the OFDR strain sensor, thereby obtaining the x-axis tension. Apply the y-axis strain characteristic to the fiber array thin film sensor. Each frame of the OFDR strain sensor output signal contains 'b' y-axis strain data. The y-axis strain array is an array formed by the y-axis strain values ​​of each row of the OFDR strain sensor, thereby obtaining the y-axis tension.

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