Flexible touch sensor based on filling structure and preparation method

Abstract

The invention relates to the technical field of bionic touch, in particular to a flexible touch sensor based on a filling structure and a preparation method. The flexible touch sensor comprises a flexible layer, and the flexible layer is provided with a containing groove. The liquid filling material is arranged in the accommodating groove; the sensing group is arranged on the side wall of the accommodating groove, the sensing group comprises a first fiber bragg grating and a second fiber bragg grating, and the first fiber bragg grating and the second fiber bragg grating are symmetrically arranged on the two side walls of the accommodating groove; and the packaging film is used for packaging the liquid filler and the sensing group. According to the embodiment of the invention, the miniature accommodating groove and the liquid filler are arranged on the flexible layer, so that the flexibility and the fitting property of the sensor can be improved, the fiber bragg gratings are symmetrically arranged on the accommodating groove, the lateral pressure has two opposite strains, and the temperature influence is eliminated through differential processing; and constant cooling and thermal diffusion stabilization effects on the sensing cavity in a dynamic environment can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bionic tactile technology, in particular to a flexible tactile sensor based on a filling structure and a pressure sensing method. BACKGROUND

[0002] With the continuous development of wearable devices, the current wearable devices have flexible functions such as bending, folding and stretching. These characteristics make flexible wearable devices have strong adaptability, and have great application potential in medical, sports and life intelligent scenes.

[0003] However, the existing flexible tactile skin usually realizes lateral pressure sensing in a piezoresistive or capacitive manner, but such sensors have problems of zero drift and insufficient repeatability under temperature changes and bending states.

[0004] The present application relates to the field of bionic tactile technology, in particular to a flexible tactile sensor based on a filling structure and a pressure sensing method. SUMMARY

[0005] One of the purposes of the present application is to provide a flexible tactile sensor based on a filling structure and a pressure sensing method to solve the problems of temperature sensitivity, lack of flexibility and difficulty in production in the prior art.

[0006] To solve the above technical problems, the embodiments of the present application are implemented as follows: In a first aspect, a flexible tactile sensor based on a filling structure is provided, comprising: a flexible layer, wherein a receiving groove is arranged on the flexible layer; a liquid filler, wherein the liquid filler is arranged in the receiving groove; a sensing group, arranged on the side wall of the receiving groove, wherein the sensing group comprises a first fiber Bragg grating and a second fiber Bragg grating, the first fiber Bragg grating and the second fiber Bragg grating are symmetrically arranged on the two side walls of the receiving groove, and are used to obtain two opposite strains under the same force; an encapsulation film, arranged at the opening of the receiving groove, used to encapsulate the liquid filler and the sensing group.

[0007] Further, the liquid filler comprises one or more liquid solvents of the main filler or the corrosion and bacteria inhibitor.

[0008] Further, the main filler comprises deionized water or saline.

[0009] Further, the flexible layer is made of silicone rubber or TPU material, and the thickness of the flexible layer is controlled to be 0.4-1.2 mm.

[0010] The second aspect also discloses a preparation method of the flexible tactile sensor based on the filling structure, and the steps comprise: cleaning and plasma activating the flexible layer made of TPU material; The microcavity structure is obtained by microprocessing on the flexible layer, and the edge of the accommodating groove is processed; Two fiber Bragg gratings are implanted on both sides of the accommodating groove, and the two fiber Bragg gratings are symmetrically distributed relative to the center line of the accommodating groove; And the liquid filler is added, and the accommodating groove is packaged by using a heat-sealing film.

[0011] The third aspect also discloses a pressure sensing method of the flexible tactile sensor based on the filling structure, and the steps comprise: The center wavelength drift of the two fiber Bragg gratings is obtained, wherein the two fiber Bragg gratings are symmetrically arranged, and the signs of the center wavelength drift of the two fiber Bragg gratings obtained are opposite; The center wavelength drift is processed by a difference elimination method, so as to eliminate the wavelength drift caused by temperature, and a difference value is obtained; The pressure value is calculated according to the difference value through a pressure formula.

[0012] Further, the center wavelength drift is the wavelength drift of the fiber Bragg grating caused by pressure and temperature, and is obtained by a wavelength change calculation formula, wherein the wavelength change calculation formula is:

[0013] wherein, is the FBG center wavelength drift; is the strain sensitivity coefficient of the FBG, and is a fixed constant; is the axial strain borne by the FBG; is the temperature sensitivity coefficient of the FBG; is the environmental temperature change.

[0014] Further, the difference value of the two fiber Bragg gratings is calculated by a difference formula, and the difference formula is:

[0015] wherein, is the difference value of the two fiber Bragg gratings. is the center wavelength shift of FBG-s1; is the center wavelength shift of FBG-s2.

[0016] Further, the tactile perception method further comprises calculating a verification value of the difference value by using a difference verification formula, and when the verification value is consistent with the difference value, the difference value is a correct value eliminating the temperature factor; the difference verification formula is:

[0017] wherein, is the center wavelength shift of FBG; is the strain sensitivity coefficient of FBG, which is a fixed constant; is the axial strain borne by FBG-s1; is the axial strain borne by FBG-s2; is the temperature sensitivity coefficient of FBG; is the environmental temperature change amount.

[0018] Further, the pressure value calculated according to the difference value by using a pressure formula is: The difference sensitivity is calculated according to the strain sensitivity of the fiber Bragg grating, and the pressure value is calculated according to a pressure calculation formula, and the pressure calculation formula is:

[0019] wherein, is the pressure; is the difference sensitivity; is the center wavelength shift of FBG.

[0020] Further, the calculation formula for calculating the difference sensitivity according to the strain sensitivity of the fiber Bragg grating is:

[0021] wherein, is the difference sensitivity; is the strain sensitivity coefficient of FBG; is the proportional coefficient of the strain and the pressure of the fiber Bragg grating.

[0022] The above technical solutions provided by the embodiments of the present application have at least the following beneficial effects: The application discloses a flexible tactile sensor based on a filling structure, which can effectively improve softness and adhesion of the sensor by opening micro containing grooves on a flexible layer and filling the containing grooves, and can reduce production requirements of the sensor array to realize mass production.

[0023] In the embodiment, the liquid filling material functions as a stress transmission medium and can realize constant cooling and stable heat diffusion of the sensing cavity in a dynamic environment.

[0024] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by the structure particularly pointed out in the written description and claims hereof.

[0025] The technical solutions of the present application are described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A schematic view of a flexible tactile sensor based on a filling structure according to an embodiment of the present application is shown in the figure; Figure 2 A schematic view of another perspective of the embodiment of the present application is shown in the figure; Figure 3 A-A sectional view of the embodiment of the present application is shown in the figure; Figure 2 Figure 4 A schematic view of liquid microcavity compression and axial strain polarity opposite to each other when lateral pressure is applied to the embodiment of the present application is shown in the figure; Figure 5 A wavelength drift curve of differential sensitivity of the embodiment of the present application is shown in the figure; Figure 6 A wavelength drift curve after differential processing of the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION​

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0028] In the present application, the word "exemplary" is used to mean "serving as an example, instance, or illustration." Any implementation described as "exemplary" in the present application is not necessarily to be construed as preferred or advantageous over other implementations. The following description is presented to enable any person skilled in the art to make and use the present application. In the following description, for purposes of explanation, specific details are set forth. It is apparent to those skilled in the art that the present application can be practiced without using these specific details. In other instances, well-known structures and processes are not elaborated in order not to obscure the description of the present application with unnecessary details. Thus, the present application is not intended to be limited by the implementations shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

[0029] The fiber Bragg grating strain refers to the change of the reflected wavelength λB when the physical properties of the grating region change, for example, are affected by strain or temperature. The change of the wavelength is closely related to the key measurement parameters such as strain and temperature, and is an important indicator in structural health monitoring.

[0030] The normal pressure refers to the force applied on the flexible tactile sensor due to the sliding of the flexible layer. The normal pressure acts on the liquid-filled microstructure, so that the two fiber Bragg gratings are subjected to the same bending strain along the sliding direction, and the strains of the two fiber Bragg gratings are the same, that is, the amplitudes of the wavelength drifts are the same and the signs are also the same, which can be offset by each other, so that the influence of the normal pressure caused by the sliding can be eliminated.

[0031] The lateral pressure, also referred to as axial pressure hereinafter, refers to the force applied on the flexible tactile sensor due to the touch of the flexible layer, which acts on the liquid-filled microstructure, and the liquid-filled microstructure causes the two fiber Bragg gratings to have equal-amplitude and opposite-sign strain.

[0032] The equal-amplitude and opposite-sign refers to the fact that when the two fiber Bragg gratings are subjected to force strain, the amplitudes of the wavelength drifts of the two fiber Bragg gratings are the same, but the signs are opposite, and the signs used for calculation can also be considered as the directions being opposite. It can be observed through experiments that the directions of the wavelength drifts of the two fiber Bragg gratings are opposite.

[0033] Before describing the embodiments of the present invention in detail, the design concept of the present invention will be summarized below.

[0034] This invention provides a flexible tactile sensor based on a filling structure, and the specific implementation is as follows. Figure 1 As shown, the core process of this invention includes: filling a microcavity structure with a liquid filler, and placing two symmetrically arranged fiber Bragg gratings within the microcavity; acquiring two strains with opposite signs, calculating the difference value through strain differential calculation, and then calculating the lateral pressure value based on this strain. The tactile sensor structure designed in this invention can effectively eliminate the strain influence caused by temperature factors, effectively improving the accuracy of acquiring lateral pressure strain.

[0035] Firstly, please refer to the appendix. Figure 1 As shown, a flexible tactile sensor based on a filling structure is also disclosed, comprising: A flexible layer 30 is provided with a receiving groove 50, wherein the receiving groove 50 is a miniature elongated groove; Liquid filler 20 is disposed within the receiving tank 50; A sensing group is provided on the side wall of the receiving groove 50. The sensing group includes a first fiber Bragg grating 10 and a second fiber Bragg grating 11. The first fiber Bragg grating 10 and the second fiber Bragg grating 11 are symmetrically provided on the two side walls of the receiving groove 50 to obtain two opposite strains under the same force. An encapsulation film is disposed at the opening of the receiving groove 50 for encapsulating the liquid filler 20 and the sensing assembly.

[0036] Understandably, to address the issue of temperature-induced crosstalk in fiber Bragg gratings leading to inaccurate pressure sensing results, an embodiment is proposed. This involves creating a micro-receptacle 50 with liquid filler 20 on the flexible layer 30, and symmetrically arranging two fiber Bragg gratings on both sides of the receptacle 50. Through the interaction between the two symmetrically arranged fiber Bragg gratings, the liquid filler 20, and the receptacle 50, pressure is coupled axially. The two fiber Bragg gratings generate two opposite axial strains, and differential processing yields an accurate sensing value that eliminates the influence of temperature.

[0037] It should be noted that the acquisition of two opposite strains under the same force includes lateral pressure caused by touch. The two opposite strains refer to the strains generated by the two fiber Bragg gratings, with the same wavelength shift amplitude (wavelength offset) when they are strained, but in opposite directions.

[0038] The embodiment adopts the flexible layer 30 and sets the micro cavity and the liquid filler 20 on the flexible layer 30, so that the inductor has a pure flexible structure, and the efficient geometric conversion from the lateral pressure to the axial strain is realized without increasing the rigid components. The differential value is read out by the differential processing method to eliminate the temperature, and the differential value is the accurate strain of the lateral pressure. The embodiment can suppress the symmetric strain caused by the bending through the symmetrically arranged double fiber Bragg gratings, so that the low zero drift, high linearity and high repeatability are obtained. The structure of the embodiment has the characteristics of thin structure, adjustable parameters, and is suitable for roll-to-roll and array manufacturing, can be spliced with the normal / tangential multi-modal pixels, and meets the requirements of large area and high consistency of wearable and robot bionic skin.

[0039] The embodiment, the liquid filler 20 plays a role of stress transfer medium, and can also realize the stable effect of constant cooling and heat diffusion of the sensing cavity in a dynamic environment. Specifically, when the cavity temperature rises due to the ambient temperature or the device self-heating, the liquid filler 20 can absorb and diffuse heat in a very short time due to the characteristics of high specific heat and fluidity, so that the local temperature field remains in an approximately constant state. The temperature gradient on both sides of the fiber Bragg grating is significantly weakened, and the thermal coupling error of the wavelength drift of the fiber Bragg grating is effectively prevented. At the same time, the liquid filler 20 and the accommodating groove form a micro “isothermal cavity”, which can still maintain the temperature balance of the area where the fiber Bragg grating is located under high-frequency pressure measurement or long-time working conditions, thereby greatly improving the temperature stability and repeatability of the sensing signal.

[0040] The embodiment using the liquid filler 20 has at least the following advantages: First, the liquid filling enhances the transmission efficiency of the normal pressure to the axial strain, and the differential sensitivity is improved to about 2 times of that of the single fiber Bragg grating. Compared with the solid colloid or air cavity structure, the bulk modulus of the liquid is lower, and higher strain transmission efficiency can be realized under a small normal load, thereby significantly improving the normal pressure sensitivity.

[0041] Second, the liquid filler forms a local heat buffer zone, effectively suppresses the temperature drift caused by the environment or self-heating, and significantly improves the wavelength stability of the fiber Bragg grating. The temperature gradient is easily formed on both sides of the fiber Bragg grating due to the uneven air heat conduction, which causes the baseline drift of the differential output. The high heat capacity and flow diffusion capacity of the liquid filling layer make the heat distribution inside the cavity uniform, which is equivalent to forming a passive constant temperature layer, effectively reducing the temperature drift coefficient Δλ / ΔT, and improving the temperature stability.

[0042] Third, the damping characteristics of the liquid inhibit high-frequency micro-disturbances, improving signal resolution. The viscous damping characteristics naturally filter high-frequency micro-vibrations, making the fiber Bragg grating output signal smoother and reducing transient noise. In particular, in low-frequency signal scenarios such as robot touch or pulse monitoring, the signal-to-noise ratio (SNR) can be improved by more than 20%.

[0043] Fourth, the design without rigid support retains skin-level flexibility, suitable for large-area wearable and robot touch arrays. The liquid-filled structure does not introduce rigid force transmission components, maintaining the overall flexibility and curlability of the sensing unit. At the same time, through the packaging of the heat-sealed film to form a sealed microcavity, the liquid plays an adaptive supporting role, avoiding signal inconsistency problems caused by micro-bubbles or mechanical gaps.

[0044] Working principle: In an embodiment, a micro-containing groove 50 is processed on the flexible layer 30, and the groove 50 is filled with a liquid filler 20. Two fiber Bragg gratings are arranged side by side on the two side walls of the containing groove 50, and the two fiber Bragg gratings are symmetrically arranged relative to the center of the containing groove 50.

[0045] When a lateral pressure is applied, the lateral pressure acts on the micro-containing groove 50. Due to the micro-long groove structure of the containing groove 50, the liquid filler 20 inside the containing groove 50 exhibits quasi-incompressible fluid characteristics under lateral pressure. The internal micro-volume displacement of the liquid filler 20 is symmetrically conducted to both sides through the side walls of the containing groove 50, and is squeezed and bent to one side, so that the lateral pressure is converted to the axial direction of the fiber Bragg grating. Since the two fiber Bragg gratings are symmetrically arranged relative to the center of the containing groove 50, the fiber Bragg grating close to the lateral pressure is compressed, and the other fiber Bragg grating is stretched. This causes two opposite strains in the two fiber Bragg gratings, i.e., two opposite sign wavelength shift values.

[0046] Further, the two opposite strains obtained are calculated by a differential processing method to obtain a wavelength drift value that eliminates temperature cross-sensitivity. The accurate lateral pressure value can be obtained by calculation. The touch sensor designed in this structure can effectively eliminate the strain influence caused by temperature factors and effectively improve the accuracy of obtaining the lateral pressure strain.

[0047] Here, the normal pressure and the axial pressure direction are perpendicular to each other.

[0048] It should be noted that the opposite signs are the center symmetry of the two fiber Bragg gratings about the containing groove 50 of the microstructure. Bending or shear deformation will cause "one tension and one compression" strain, for example, if the first fiber Bragg grating (FBG-S1) is in tension, the second fiber Bragg grating (FBG-S2) will be in compression. (positive sign, i.e. positive strain value); if, the second fiber Bragg grating 11 (FBG-S2) is under compression strain (negative sign, i.e. negative strain value), and i.e. "equal amplitude and opposite sign".

[0049] Reference is made to the accompanying drawings Figure 2 and 3 Further, the liquid filler 20 comprises one or more than one liquid solvent of the main filler or the preservative and bacteriostatic agent. Further, the main filler comprises deionized water or saline.

[0050] Reference is made to the accompanying drawings Figure 4 Here, the liquid filler 20 is mainly constrained by the accommodation groove 50 under the flow characteristics of the liquid under extrusion when the lateral pressure is applied. The lateral extrusion makes the accommodation groove 50 into a sealed structure, and the liquid filler 20 makes the accommodation groove 50 bulge around, and the opposite sign axial strain is generated on the two side walls of the accommodation groove 50, i.e. the fiber Bragg grating (FBG-S1) arranged on the stress side is under compression, and the fiber Bragg grating (FBG-S2) on the other side is under tension.

[0051] In some embodiments, deionized water is used as the liquid filler 20, which is filled into the accommodation groove 50 of the flexible layer 30 and packaged by the heat-sealed film. In some other embodiments, a mixture of medical saline and preservative and bacteriostatic agent is used as the liquid filler 20, which is filled into the accommodation groove 50 of the flexible layer 30 and packaged by the heat-sealed film. In some other embodiments, a mixture of deionized water and preservative and bacteriostatic agent is used as the liquid filler 20, which is filled into the accommodation groove 50 of the flexible layer 30 and packaged by the heat-sealed film.

[0052] Here, the preservative and bacteriostatic agent comprises hypochlorite, sulfite, isothiazolinone compound, etc., which only needs a small amount to play an antibacterial role.

[0053] Based on the same inventive concept, the second aspect further discloses a preparation method of the flexible tactile sensor based on the filling structure, which comprises the following steps: Step 001: cleaning and plasma activation treatment of the flexible layer 30 made of TPU material.

[0054] In some embodiments, the thickness of the flexible layer 30 is controlled to be 0.4-1.2 mm. In some embodiments, the flexible layer 30 made of silicone rubber is 0.8 mm. In some other embodiments, the flexible layer 30 made of TPU material is 0.4 mm. In some other embodiments, the flexible layer 30 made of TPU material is 1.2 mm.

[0055] Step 002: The micro-machining process on the flexible layer 30 obtains the micro-cavity structure containing groove 50, and the edge of the containing groove 50 is processed.

[0056] Specifically, the micro-cavity structure containing groove 50 is micro-machined on the flexible layer 30, and the containing groove 50 is processed by a micro-machining process, which is a parallel slit and a boundary trimming process. The micro-machining process includes laser, molding and micro-milling machining processes.

[0057] In an embodiment, the containing groove 50 is machined along the axis direction of the FBG to be laid, wherein the length of the containing groove 50 is controlled to be 2-10 mm, the width is controlled to be 100-600 μm, and the height is controlled to be 30-200 μm.

[0058] In some embodiments, the containing groove 50 is machined on the flexible layer 30 along the axis direction of the FBG to be laid by a laser process, wherein the length of the containing groove 50 is controlled to be 10 mm, the width is controlled to be 600 μm, and the height is controlled to be 200 μm. In other embodiments, the containing groove 50 is machined on the flexible layer 30 along the axis direction of the FBG to be laid by a micro-milling process, wherein the length of the containing groove 50 is controlled to be 5 mm, the width is controlled to be 100 μm, and the height is controlled to be 100 μm. In still other embodiments, the containing groove 50 is machined on the flexible layer 30 along the axis direction of the FBG to be laid by a laser process, wherein the length of the containing groove 50 is controlled to be 2.5 mm, the width is controlled to be 400 μm, and the height is controlled to be 30 μm.

[0059] Step 003: Two fiber Bragg gratings are implanted on both sides of the containing groove 50, and the two fiber Bragg gratings are symmetrically distributed relative to the center line of the containing groove 50.

[0060] It can be understood that, in order to obtain the axial strain of the two different fiber Bragg gratings under lateral pressure, the difference value is calculated by the two axial strains, and the difference value can effectively eliminate the temperature factor. That is, in an embodiment, the symmetric arrangement suppresses the symmetric strain caused by bending, thereby obtaining low zero drift, high linearity and high repeatability.

[0061] In an embodiment, the two fiber Bragg gratings are parallel, and the effective grating length of the two fiber Bragg gratings is controlled to be 2-8 mm. The two fiber Bragg gratings are symmetrically arranged on both sides of the containing groove 50, and a 10-50 μm thin glue layer is used to solidify and correct the centering so that the spacing between the two is controlled to be 0.8-2.0 mm. This process ensures that the two are equidistant from the center line of the liquid filler 20 with an error of ≤±50 μm.

[0062] In some embodiments, the effective grating length of the two fiber Bragg gratings is controlled to be 6 mm; in some embodiments, the effective grating length of the two fiber Bragg gratings is controlled to be 8 mm; in some other embodiments, the effective grating length of the two fiber Bragg gratings is controlled to be 2 mm.

[0063] Step 004: and add the liquid filler 20, using a heat-seal film to package the accommodation groove 50.

[0064] It can be understood that the liquid filler 20 is filled into the accommodation groove 50, and the liquid filler 20 is perfusion water or saline. In order to ensure that the liquid filler 20 and the fiber Bragg grating are fixed correspondingly, the embodiment is packaged by the packaging film, and a period of time is needed for static placement for exhaust, and then the heat-seal film is covered for heat compression sealing.

[0065] In an embodiment, in order to verify the flexible tactile sensor based on the negative Poisson's ratio, the stress release package is performed at the end and the demodulation module is connected, the lateral, temperature and bending combined calibration and aging reliability are tested, and the (p, T) parameters are derived and solidified to the device, so as to obtain the verification data.

[0066] In an embodiment, this step is an experimental verification, which is tested by a calibration process including controlling the lateral pressure to be 0-60 kPa, controlling the temperature to be 20-60℃ and controlling the bending radius to be R=30-150 mm, fitting the differential sensitivity , temperature residual error and bending crosstalk ratio, and locking the process window of the accommodation groove 50 size, film thickness and liquid viscosity to support array production.

[0067] Based on the same inventive concept, a third aspect provides a tactile sensing method of a flexible tactile sensor based on a filling structure, and the steps include: Step S100: obtaining the center wavelength drift of the two fiber Bragg gratings, wherein the two fiber Bragg gratings are symmetrically arranged, and the signs of the center wavelength drift of the two fiber Bragg gratings obtained are opposite.

[0068] It can be understood that by obtaining the wavelength drift of each fiber Bragg grating, the wavelength drift here includes the wavelength drift caused by axial strain and temperature, and since the wavelength drift includes the wavelength drift caused by temperature, the fiber Bragg grating is prone to inaccurate problems when detecting lateral pressure.

[0069] In the embodiment, the micro-structure accommodating groove 50 is provided with two symmetrical fiber Bragg gratings on two sides of the accommodating groove 50. When the lateral pressure is applied, the two symmetrical fiber Bragg gratings generate two opposite axial strains, i.e. two opposite wavelength shift amounts. The two opposite wavelength shift amounts can be processed to offset the wavelength shift amount caused by temperature, so as to automatically eliminate the temperature error, i.e. to reduce the temperature cross-sensitivity.

[0070] Here, the center wavelength of the light wave drifts due to the strain of the fiber Bragg grating under various factors. The center wavelength drift amount includes the light wave drift amplitude and the drift sign. The drift sign is used to indicate the wavelength drift direction. In the formula, the temperature and the lateral pressure are considered.

[0071] The principle of obtaining the axial strain is explained as follows: the axial strain borne by the FBG is calculated by the pressure-strain relationship formula of the FBG. That is, the strain changes with the pressure. The pressure value can be obtained by detecting the strain. The pressure-strain relationship formula is as follows:

[0072] Among them, is the axial strain, is the geometric / material coupling coefficient, is the pressure.

[0073] In addition, the liquid filler 20 is arranged at the middle position of the two fiber Bragg gratings. When the lateral pressure is applied, one of the fiber Bragg gratings is in tensile strain axial strain is positive, and the other fiber Bragg grating is in tensile strain axial strain is negative.

[0074] Further, the center wavelength shift amount is the wavelength drift of the fiber Bragg grating caused by the pressure and the temperature, which is calculated by the wavelength change calculation formula. The wavelength change calculation formula is as follows:

[0075] Among them, is the FBG center wavelength shift; is the strain sensitivity coefficient of the FBG, which is a fixed constant; is the axial strain borne by the FBG; is the temperature sensitivity coefficient of the FBG; is the environmental temperature change amount.

[0076] In the embodiment, two fiber Bragg gratings are arranged side by side on both sides of the accommodating groove 50, one of which is FBG-s1 and the other is FBG-s2, and the two fiber Bragg gratings are symmetrically arranged with respect to the center of the accommodating groove 50. When a lateral pressure is applied, the lateral pressure and the liquid filler 20 in the accommodating groove 50 cooperate to cause two opposite strains of the two fiber Bragg gratings, that is, two center wavelength shift values of opposite signs are obtained.

[0077] The wavelength shift of each fiber Bragg grating is calculated by the wavelength change calculation formula, and finally the signs of the center wavelength shift values of the two fiber Bragg gratings are opposite.

[0078] Step S200: The center wavelength shift value is processed by a difference elimination method to eliminate the wavelength drift value caused by temperature, and a difference value is obtained.

[0079] Further in the embodiment, the difference value is obtained by processing the strain signal by the elimination method, that is, the difference value of the two fiber Bragg gratings is calculated by a difference formula, and the difference formula is:

[0080] Wherein, is the difference value of the two fiber Bragg gratings; is the center wavelength shift value of FBG-s1; is the center wavelength shift value of FBG-s2.

[0081] Further in the embodiment, the tactile sensing method further includes calculating a verification value of the difference value by using a difference verification formula, and when the verification value is consistent with the difference value, the difference value is a correct value eliminating the temperature factor; and the difference verification formula is:

[0082] Wherein, is the FBG wavelength shift value; is the strain sensitivity coefficient of FBG, which is a fixed constant; is the axial strain borne by FBG-s1; is the axial strain borne by FBG-s2; is the temperature sensitivity coefficient of FBG; is the environmental temperature change value.

[0083] It should be noted that the symmetric arrangement in the microstructure makes After substituting the difference formula, the temperature term Therefore, the temperature interference is completely eliminated, and the temperature sensitive problem caused by temperature change is eliminated. In the embodiment, the two FBGs are symmetrically arranged to be subjected to the same temperature change, and the differential processing is equivalent to subtracting the same interference term, so that the influence of temperature on the sensing signal is finally eliminated.

[0084] Moreover, since the wavelength drifts of FBG-s1 and FBG-s2 arranged symmetrically are opposite in sign and equal in amplitude, the drift amplitude is the same, and the calculation sign is opposite, so In combination with the strain amplification characteristics of the negative Poisson ratio, the differential sensitivity is finally improved to , which is much higher than that of a single FBG, greatly improving the differential sensitivity, that is, the bending sensitivity.

[0085] It should be further pointed out that when the flexible tactile sensor is subjected to normal pressure, since the first fiber Bragg grating 10 and the second fiber Bragg grating 11 are symmetrically arranged at a small position, the normal pressure received by the two is the same, and is a normal strain, that is, the wavelength drift amplitude caused by the normal pressure of the two is the same, and the drift sign is also the same. It can be known through the above wavelength change calculation formula and differential formula calculation that the differential value caused by the normal is zero, that is, the cross sensitivity caused by the normal pressure is reduced.

[0086] It should be further pointed out that when the flexible tactile sensor is subjected to normal pressure, since the first fiber Bragg grating 10 and the second fiber Bragg grating 11 are symmetrically arranged at a small position, the normal pressure received by the two is the same, and is a normal strain, that is, the wavelength drift amplitude caused by the normal pressure of the two is the same, and the drift sign is also the same. It can be known through the above wavelength change calculation formula and differential formula calculation that the differential value caused by the normal is zero, that is, the cross sensitivity caused by the normal pressure is reduced.

[0087] Step S300: calculating the pressure value according to the differential value through the pressure formula.

[0088] In the embodiment, the pressure value is calculated according to the differential value through the pressure formula, which is The differential sensitivity is calculated according to the strain sensitivity of the fiber Bragg grating, and the pressure value is calculated according to the pressure calculation formula. The pressure calculation formula is

[0089] wherein, P is the pressure; is the differential sensitivity; is the FBG center wavelength offset.

[0090] In the embodiment, the calculation formula for calculating the differential sensitivity according to the strain sensitivity of the fiber Bragg grating is

[0091] wherein, is the differential sensitivity; is the strain sensitivity coefficient of FBG; is the proportional coefficient of FBG strain and pressure.

[0092] In actual environment, there is a residual upper bound when the temperature is not completely consistent If there is still a small temperature difference on both sides of the accommodating groove 50, so that The differential formula is:

[0093] Since the embodiment adopts the liquid filler 20, and the isothermal effect of the liquid filler 20 further reduces the residual temperature drift term and eliminates the influence of temperature.

[0094] In summary, the strain obtained by the method can effectively eliminate the influence of temperature, that is, the differential processing method obtains the strain eliminating the influence of temperature, and the lateral pressure value is calculated according to the strain. Through the structure design of the tactile sensor, the crosstalk influence caused by the temperature factor can be effectively eliminated, and the accuracy of obtaining the lateral pressure strain can be effectively improved.

[0095] Figure 5 The differential sensitivity curve of wavelength drift under lateral pressure can be obviously observed, and the wavelength drift amplitude of FBG-S1 and FBG-S2 is approximately the same, and the direction is opposite, and the differential value is twice the drift amplitude of a single FBG, and the sensitivity is obviously greatly improved. Figure 6 The wavelength drift curve after temperature elimination can be known, and the pressure response curve under temperature change can be known, and the temperature is approximately eliminated.

[0096] Based on the same inventive concept, the fourth aspect also discloses an application method of the flexible tactile sensor based on the filling structure, and the flexible tactile sensor based on the filling structure is applied to wearable health monitoring, robot tactile and human-computer interaction application scenarios.

[0097] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. The present disclosure is not limited to the precise structure described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is only limited by the appended claims. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.​

Claims

1. A flexible tactile sensor based on a filling structure, characterized by, The application relates to a flexible layer provided with a containing groove, a liquid filler arranged in the containing groove, an inductive group arranged on the side wall of the containing groove, a packaging film arranged at the opening of the containing groove for packaging the liquid filler and the inductive group. The liquid filler comprises one or more than one liquid solvent of a main filler or an antiseptic bacterium inhibitor. The main filler comprises deionized water or saline. The flexible layer is made of silicone rubber or TPU material, and the thickness of the flexible layer is controlled to be 0.4-1.2 mm. The application further relates to a manufacturing method of the flexible layer.

2. The haptics-aware method of claim 1, wherein, The flexible layer made of TPU material is cleaned and subjected to plasma activation treatment.

3. The haptics-aware method of claim 2, wherein, The containing groove with a microcavity structure is machined on the flexible layer through a micro-machining process, and the edge of the containing groove is treated.

4. The haptic-aware method of claim 1, wherein, Two fiber Bragg gratings are implanted on the two sides of the containing groove, and the two fiber Bragg gratings are symmetrically distributed relative to the center line of the containing groove.

5. A method of fabricating a flexible tactile sensor based on a filling structure, characterized by the steps of The liquid filler is added, and the containing groove is packaged by using a heat-sealing film. The application further relates to a method for calculating the pressure value. The application further relates to a method for calculating the pressure value. The application further relates to a method for calculating the pressure value. The application further relates to a method for calculating the pressure value.

6. A method of pressure sensing based on a flexible tactile sensor of filled structures, characterized by the steps of The application further relates to a method for calculating the pressure value. The application further relates to a method for calculating the pressure value. The application further relates to a method for calculating the pressure value. The application further relates to a method for calculating the pressure value.

7. The pressure-aware method of claim 6, wherein, The application further relates to a method for calculating the pressure value. ； wherein, is the FBG center wavelength offset amount; is the strain sensitivity coefficient of the FBG, and is a fixed constant; is the axial strain borne by the FBG; is the temperature sensitivity coefficient of the FBG; is the environmental temperature change amount.

8. The pressure-aware method of claim 6, wherein, The application further relates to a method for calculating the pressure value. wherein, is a difference value of two fiber Bragg gratings; is a center wavelength shift amount of FBG-s1; is a center wavelength shift amount of FBG-s2.

9. The pressure-aware method of claim 6, wherein, The application further relates to a method for calculating the pressure value. The application further relates to a method for calculating the pressure value. ； wherein is the pressure; is the differential sensitivity; is the differential value of the two fiber Bragg gratings.

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