Dual-mode tactile sensor and method capable of realizing quantitative detection of elastic modulus

Abstract

The invention discloses a dual-mode touch sensor capable of realizing quantitative detection of elastic modulus and a method. A dual-mode sensing device of the dual-mode touch sensor detects a pressure strain electric signal when the surface of a detected object generates force deformation, and a data acquisition and processing device acquires the electric signal and performs data processing according to a specific elastic modulus detection model, so that quantitative detection of the elastic modulus of the material is realized. The method comprises the steps that a measured object is placed on a platform, and the axis of a sensor is kept perpendicular to a measured surface; positive pressure is loaded at the top of the probe at a constant speed to push the spherical probe to be pressed into the to-be-measured object at a constant speed; a voltage signal is collected through the data collecting and processing device, and the model measures the Poisson's ratio and detects the elastic modulus. According to the dual-mode touch sensor and the method, the Poisson's ratio of the material is accurately measured, the elastic modulus is quantified, a robot can recognize the mechanical performance of an unknown material, and finer perception and interaction are achieved.

Description

Technical Field

[0001] The present invention relates to a dual-mode tactile sensor, and in particular to a dual-mode tactile sensor and a method for realizing quantitative detection of elastic modulus. Background Art

[0002] With the widespread application of robotics, the range of objects robots can interact with continues to expand, placing increasing demands on the tactile perception accuracy of manipulators. Softness and hardness perception directly impacts the ability of dual-mode tactile sensors to accurately identify an object's surface characteristics, shape, and texture. Quantifying softness and hardness properties is closely related to elastic modulus. Elastic modulus is a physical quantity that measures a material's ability to resist deformation and is typically determined through compression, tension, or shear testing. A higher elastic modulus indicates a stiffer material and a lower deformation; conversely, a material with a lower elastic modulus is softer and more susceptible to larger deformation. Current dual-mode tactile sensors have limitations in quantitatively detecting softness and hardness properties. They simply compare material stiffness to achieve qualitative differentiation and are unable to quantitatively determine the softness or hardness of an object by quantifying the elastic modulus when the Poisson's ratio of the material is unknown. Alternatively, simply assuming the Poisson's ratio of a soft material prevents accurate elastic modulus determination. Summary of the Invention

[0003] In order to solve the problems existing in the background technology, the present invention provides a dual-mode tactile sensor and method that can realize quantitative detection of elastic modulus.

[0004] The technical solution adopted in the present invention is:

[0005] 1. A dual-mode tactile sensor capable of quantitatively detecting elastic modulus, comprising:

[0006] shell.

[0007] The flexible gated strain sensing unit is installed on the top surface of the housing and is used to detect the voltage signal generated when the unit is deformed.

[0008] The spherical probe is crimped and installed directly above the flexible gated strain sensing unit, and the lower end is sequentially inserted into the center of the flexible gated strain sensing unit and the housing and contacts the surface of the object to be measured below. When the spherical probe is pressed down, the flexible gated strain sensing unit is deformed.

[0009] The flexible piezoresistive pressure sensing unit is mounted on the top surface of the spherical probe and is used to detect the voltage signal generated when the flexible piezoresistive pressure sensing unit is subjected to an external load.

[0010] The data acquisition and processing device is electrically connected to the flexible piezoresistive pressure sensing unit and the flexible gated strain sensing unit and is used to obtain the elastic modulus of the measured object by detecting the received voltage signal.

[0011] The shell is a hollow cylinder with a through top, the bottom of the shell is a through hollow inverted cone, and the center of the bottom surface of the shell is a first through hole; the flexible gated strain sensing unit is a cross-beam structure and a second through hole of the same size as the first through hole is opened in the center, and the bottom surfaces of the four cross beam ends of the flexible gated strain sensing unit are crimped to the edge of the top surface of the shell; the upper part of the spherical probe is a horizontal plate-like body, the middle part is provided with a crimping block, the lower part is a vertical cylindrical body and the bottom end is hemispherical, the top surface of the crimping block and the bottom center of the upper plate-like body of the spherical probe are integrally formed, and the bottom center of the crimping block and the lower cylindrical body of the spherical probe are integrally formed. The top of the body is integrally formed; in the initial state, the flexible gated strain sensing unit is in an undeformed state, the bottom surface of the crimping block of the spherical probe contacts the center of the top surface of the flexible gated strain sensing unit, the lower cylindrical body of the spherical probe is inserted into the first through hole and the second through hole, and the bottom end of the spherical probe is located inside the first through hole and tangent to the center of the outer bottom surface of the shell, the bottom end of the spherical probe and the center of the outer bottom surface of the shell jointly contact the surface of the object to be measured, the bottom surface of the shell contacts the plane of the object to be measured, and the spherical probe is perpendicular to the plane of the object to be measured; the flexible piezoresistive pressure sensing unit is installed at the center of the top surface of the upper plate-shaped body of the spherical probe.

[0012] The data acquisition and processing device includes a voltage divider module, a voltage acquisition module, a data processing module, and a host computer module, which are connected in sequence. The voltage divider module is electrically connected to a flexible piezoresistive pressure sensor unit and a flexible gated strain sensor unit. The data processing module processes the collected voltage signals using a specific algorithm, and the host computer module reads and displays the data results.

[0013] The flexible gated strain sensing unit includes a polydimethylsiloxane (PDMS) packaging film, a polydimethylsiloxane (PDMS) substrate, and four fluid resistor microstructures. The polydimethylsiloxane (PDMS) packaging film and the polydimethylsiloxane (PDMS) substrate are both cross-beam structures with concentric second through holes at their centers. The top centers of the four crossbeams of the polydimethylsiloxane (PDMS) substrate are each provided with a mounting groove. The four fluid resistor microstructures are respectively installed in one of their respective mounting grooves. The polydimethylsiloxane (PDMS) packaging film is installed on the top surface of the polydimethylsiloxane (PDMS) substrate and encapsulates the four fluid resistor microstructures. The bottom surface of the crimping block of the spherical probe is crimped to the center of the top surface of the polydimethylsiloxane (PDMS) packaging film. Conductive metal wires are respectively led out from both ends of each fluid resistor microstructure, one of the conductive metal wires of each fluid resistor microstructure is grounded, and the other conductive metal wire is electrically connected to a voltage divider module.

[0014] The flexible piezoresistive pressure sensing unit includes a polyimide PI (Polyimide Film) film, a piezoresistive sensitive sheet and an interdigital electrode. The piezoresistive sensitive sheet is encapsulated between the polyimide PI film and the interdigital electrode. The interdigital electrode is provided with two pins. The negative electrode of the interdigital electrode is grounded through one pin, and the positive electrode of the interdigital electrode is electrically connected to the voltage divider module through the other pin.

[0015] 2. A method for quantitatively detecting the elastic modulus of a dual-mode tactile sensor, comprising:

[0016] Step S1: Place the object to be measured horizontally on the loading platform, install the dual-mode tactile sensor directly above the object to be measured, keep the axis of the spherical probe coincident with the normal of the top surface of the object to be measured, make the bottom surface of the shell parallel to the top surface of the object to be measured, and start the data acquisition and processing device.

[0017] Step S2: Stably and uniformly load a uniform positive pressure on the top surface of the spherical probe through the loading surface, so that the loading surface completely covers the flexible piezoresistive pressure sensing unit, and push the spherical probe into the object to be tested at a uniform speed. The pressing depth does not exceed the radius of the hemispherical pressure head at the bottom end of the spherical probe, and at the same time, the flexible gated strain sensing unit is deformed.

[0018] Step S3: The five-channel voltage signals transmitted by the four fluid resistance microstructures of the flexible piezoresistive pressure sensing unit and the flexible gated strain sensing unit are read through the voltage acquisition single module of the data acquisition and processing device. Then, the elastic modulus of the object being measured is obtained and displayed after being processed by the elastic modulus quantitative detection algorithm installed in the data acquisition and processing device, thereby realizing quantitative detection of the elastic modulus.

[0019] In step S3, the voltage divider module of the data acquisition and processing device receives the five-channel voltage signal and transmits it to the data processing module through the voltage acquisition module. The elastic modulus quantitative detection algorithm is installed in the data processing module. The first step of the elastic modulus quantitative detection algorithm is to first obtain the contact force F between the spherical probe and the object to be measured based on the five-channel voltage signal. i The second step of the elastic modulus quantitative detection algorithm is to calculate the contact force F between the spherical probe and the object to be tested. i The Poisson's ratio v of the object to be measured is obtained by combining the Hertz contact theory and the finite element analysis method with the indentation depth δ of the spherical probe into the object to be measured. The third step of the elastic modulus quantitative detection algorithm is to obtain the elastic modulus of the object to be measured based on the indentation depth δ of the spherical probe into the object to be measured and the Poisson's ratio v of the object to be measured, and transmit it to the host computer module for display.

[0020] In the first step of the elastic modulus quantitative detection algorithm, the loaded uniform positive pressure F is obtained based on the relationship between the voltage signal of the flexible piezoresistive pressure sensing unit and the loaded uniform positive pressure, and then the contact force F between the spherical probe and the object to be measured is obtained. i , as follows:

[0021] F i =F-4F0cosα

[0022] Wherein, F0 is the average force on the four beams of the flexible gated strain sensing unit; α is the angle between the flexible gated strain sensing unit and the vertical axis after deformation.

[0023] Based on the four-channel voltage signals transmitted by the four fluid resistor microstructures of the flexible gated strain sensing unit, the strain ε of the flexible gated strain sensing unit along the stretching direction is obtained. l , and then the penetration depth δ of the spherical probe into the object to be measured is obtained. The penetration depth δ of the spherical probe into the object to be measured is equal to the vertical movement distance z of the deformation center of the flexible gated strain sensing unit, which is as follows:

[0024]

[0025] Where l is the horizontal length of the flexible gated strain sensing unit, ε l is the strain of the flexible gated strain sensing unit along the stretching direction, which is equal to the ratio of the length change of the flexible gated strain sensing unit along the stretching direction to the initial length, and can be calculated according to the strain sensitivity curve.

[0026] In the second step of the elastic modulus quantitative detection algorithm, based on the contact force F between the spherical probe and the object to be measured, i As well as the penetration depth δ of the spherical probe into the object to be measured, the correction factor к related to the radius R of the hemispherical indenter at the bottom end of the spherical probe, the thickness H of the object to be measured, the Poisson's ratio v of the object to be measured, and the penetration depth δ of the spherical probe into the object to be measured is established by finite element simulation software using Hertz contact theory and finite element analysis method, as follows:

[0027]

[0028] Among them, F Y and F H are the contact forces F between the spherical probe and the object to be measured, respectively. i Finite element solution and Hertz solution of .

[0029] The correction factor к is optimized by the finite element analysis method to obtain the optimized correction factor к′, which is as follows:

[0030]

[0031] Here, β is the β factor related to the Poisson’s ratio v of the object to be measured and the penetration depth δ of the spherical probe into the object to be measured in the finite element analysis method, which represents the influence of the Poisson’s ratio and large deformation on the contact process.

[0032] The contact force F between the spherical probe and the object to be measured is adjusted using the optimized correction factor к′. i Make corrections as follows:

[0033] F i ′=(c+cβ*δ / H)δ 3 / 2

[0034]

[0035] Among them, F i ′ is the corrected contact force between the objects to be measured; c is the intercept; E is the elastic modulus of the object to be measured in the finite element analysis, which is obtained from the elastic modulus of the hemispherical indenter of the spherical probe E 11 and the elastic modulus E′ of the object to be measured.

[0036] Establish F i ′ / δ 3 / 2 -δ / H curve, based on the corrected contact force F between the objects to be measured i The linear relationship between the Poisson's ratio v and the β factor of the object to be measured is extracted from the relationship curve of ′, and the Poisson's ratio v of the object to be measured is obtained after interpolation.

[0037] In the third step of the elastic modulus quantitative detection algorithm, the elastic modulus E′ of the object to be measured is as follows:

[0038]

[0039] Among them, F i ' is the corrected contact force between the objects to be measured; R1 is the curvature radius of the indenter.

[0040] According to the Hertz contact formula, the elastic modulus and contact force F are established i The relationship between ′ and the indentation depth δ. By considering the indenter as a rigid sphere and the object to be measured as a plane, the Hertz contact formula is simplified and the calculation formula of the elastic modulus is derived.

[0041] The beneficial effects of the present invention are:

[0042] The dual-mode tactile sensor and method of the present invention utilize the synergistic effect of dual-mode sensing to realize the extraction of force-displacement information in the contact measurement process. By accurately measuring the Poisson's ratio of the material, the measurement accuracy of the elastic modulus is greatly improved, which helps robots to quantitatively identify the soft and hard properties and mechanical properties of unknown materials, and achieve more refined perception and interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the dual-mode sensor structure, where: Figure 1 (a) is the overall structure diagram of the dual-mode sensor. Figure 1 (b) is the exploded diagram of the dual-mode sensor structure;

[0044] Figure 2 The exploded diagram of the flexible gated strain sensing unit structure;

[0045] Figure 3 It is a schematic diagram of the structure of a flexible piezoresistive pressure sensing unit, where: Figure 3 (a) is the exploded diagram of the pressure sensing unit structure. Figure 3 (b) is a schematic diagram of the interdigital electrode structure;

[0046] Figure 4 Schematic diagram of the spherical probe structure;

[0047] Figure 5 is a schematic diagram of the shell structure, where Figure 5 (a) is a three-dimensional diagram of the shell, Figure 5 (b) is a front view of the housing;

[0048] Figure 6 It is a connection diagram of the data acquisition and processing device;

[0049] Figure 7 This is the principle diagram of the dual-mode sensor detection process, where: Figure 7 (a) is a schematic diagram of the deformation of the flexible gate-controlled strain sensing unit at the end of the pressing stroke. Figure 7 (b) is a deformation diagram of the flexible gated strain sensing unit;

[0050] Figure 8 This is a performance test diagram of the flexible piezoresistive pressure sensing unit, where: Figure 8 (a) is the sensitivity curve of the pressure sensing unit under the positive pressure of 0kPa ~ 300kPa, Figure 8 (b) is the response time diagram of the piezoresistive sensing unit during the loading / unloading process under a pressure of 1N. Figure 8 (c) is a stability curve of the piezoresistive sensing unit after 1200 cycles under a pressure of 5N;

[0051] Figure 9The resistance change rate and minimum detection limit of the flexible gated strain sensor unit in the uniaxial tensile test are plotted, where Figure 9 (a) is the sensitivity diagram of the strain sensing unit, Figure 9 (b) is the minimum detection limit diagram of the strain sensing unit;

[0052] Figure 10 This is the load calibration test diagram of the dual-mode sensor, where: Figure 10 (a) Load calibration diagram of the piezoresistive pressure cell, Figure 10 (b) Load calibration diagram of the strain sensing unit;

[0053] Figure 11 is the displacement-resistance change rate curve of the dual-mode sensor;

[0054] Figure 12 is a graph of the correction factor к and the dimensionless indentation depth δ / H for different thicknesses H of the object to be measured, where Figure 12 (a) is a graph of the correction factor к and the dimensionless indentation depth δ / H when the thickness of the object to be measured is H2 = 20 mm. Figure 12 (b) is a graph of the correction factor к and the dimensionless indentation depth δ / H when the thickness of the object to be measured is H3 = 30 mm. Figure 12 (c) is a graph of the correction factor к and the dimensionless indentation depth δ / H when the thickness of the object to be measured is H4=40mm. Figure 12 (d) is a graph of the correction factor к and the dimensionless indentation depth δ / H when the thickness of the object to be measured is H5 = 50 mm;

[0055] Figure 13 F is the pressure during the indentation process under different thickness H of the object to be tested i ′ / δ 3 / 2 -δ / H curve, where Figure 13 (a) is the F during the pressing process when the thickness of the object to be tested is H2 = 20mm i ′ / δ 3 / 2 -δ / H curve, Figure 13 (b) is the F during the pressing process when the thickness of the object to be tested is H3 = 30mm i ′ / δ 3 / 2 -δ / H curve, Figure 13 (c) is the F during the pressing process when the thickness of the object to be tested is H4 = 40mm i ′ / δ 3 / 2 -δ / H curve, Figure 13 (d) is the F during the pressing process when the thickness of the object to be tested is H5 = 50mm i ′ / δ 3 / 2 -δ / H curve;

[0056] Figure 14is the relationship between β factor and Poisson's ratio v under different elastic moduli, where Figure 14 (a) is the relationship between the β factor and Poisson's ratio v when the elastic modulus E1 = 5MPa, Figure 14 (b) is the relationship between the β factor and Poisson's ratio v when the elastic modulus E2 = 10 MPa. Figure 14 (c) is the relationship between the β factor and Poisson's ratio v when the elastic modulus E3 = 15 MPa. Figure 14 (d) is the relationship between the β factor and the Poisson's ratio v when the elastic modulus E4 = 20 MPa;

[0057] Figure 15 This is the post-processing diagram of the experimental results of Poisson's ratio estimation, where Figure 15 (a) is the F of the three objects to be tested i ′ / δ 3 / 2 -δ / H relationship curve, Figure 15 (b) is the accuracy graph of Poisson’s ratio estimation;

[0058] Figure 16 is the Poisson's ratio estimation diagram of the dual-mode sensor, where Figure 16 (a) is the distribution diagram of the β factor obtained by the dual-mode sensor in the β-v diagram, Figure 16 (b) is the accuracy graph of Poisson’s ratio estimation;

[0059] Figure 17 is the test result and accuracy diagram of elastic modulus, where: Figure 17 (a) is a comparison chart of the elastic modulus test results after Poisson’s ratio measurement and the standard test results. Figure 17 (b) is a comparison chart of the elastic modulus results and accuracy obtained by assuming Poisson's ratio and measuring Poisson's ratio;

[0060] In the figure: 1. Flexible piezoresistive pressure sensing unit, 2. Spherical probe, 3. Flexible gated strain sensing unit, 4. Housing, 5. Polydimethylsiloxane (PDMS) packaging film, 6. Polydimethylsiloxane (PDMS) substrate, 7. Polyimide (PI) film, 8. Piezoresistive sensitive sheet, 9. Interdigital electrode, 10. Data processing module, 11. Voltage acquisition module, 12. Voltage divider module, 13. Host computer module. DETAILED DESCRIPTION

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0062] like Figure 1 (a) and Figure 1As shown in (b), the dual-mode tactile sensor of the present invention that can realize quantitative detection of elastic modulus includes a flexible piezoresistive pressure sensing unit 1, a spherical probe 2, a flexible gated strain sensing unit 3 and a shell 4. The flexible gated strain sensing unit 3 is installed on the top surface of the shell 4 and is used to detect the voltage signal generated when it is deformed; the spherical probe 2 is crimped and installed directly above the flexible gated strain sensing unit 3, and the lower end is sequentially inserted into the center of the flexible gated strain sensing unit 3 and the shell 4 and contacts the surface of the object to be measured below. When the spherical probe 2 is pressed down, the flexible gated strain sensing unit 3 is deformed; the flexible piezoresistive pressure sensing unit 1 is installed on the top surface of the spherical probe 2 and is used to detect the voltage signal generated when it is subjected to an external load; the flexible piezoresistive pressure sensing unit 1, the spherical probe 2, the flexible gated strain sensing unit 3 and the shell 4 constitute a dual-mode sensing device. The data acquisition and processing device is electrically connected to the flexible piezoresistive pressure sensing unit 1 and the flexible gated strain sensing unit 3 and is used to obtain the elastic modulus of the measured object by detecting the received voltage signal.

[0063] like Figure 5 As shown, the shell 4 is a hollow cylinder with a through top, the bottom of the shell 4 is a through hollow inverted cone, and the center of the bottom surface of the shell 4 is a first through hole; the flexible gated strain sensing unit 3 is a cross-beam structure and a second through hole of the same size as the first through hole is opened in the center, and the bottom surfaces of the four cross beam ends of the flexible gated strain sensing unit 3 are crimped to the top edge of the shell 4; the upper part of the spherical probe 2 is a horizontal plate-like body, and a crimping block is provided in the middle part, and the lower part is a vertical cylindrical body and the bottom end is hemispherical, the top surface of the crimping block and the bottom center of the upper plate-like body of the spherical probe 2 are integrally formed, and the bottom center of the crimping block and the top of the lower cylindrical body of the spherical probe 2 are formed integrally. The ends are integrally formed; in the initial state, the flexible gated strain sensing unit 3 is in an undeformed state, the bottom surface of the crimping block of the spherical probe 2 contacts the top surface center of the flexible gated strain sensing unit 3, the lower cylindrical body of the spherical probe 2 is inserted into the first through hole and the second through hole, and the bottom end of the spherical probe 2 is located inside the first through hole and is tangent to the center of the outer bottom surface of the outer shell 4, the bottom end of the spherical probe 2 and the center of the outer bottom surface of the outer shell 4 jointly contact the surface of the object to be measured, the bottom surface of the outer shell 4 contacts the plane of the object to be measured, and the spherical probe 2 is perpendicular to the plane of the object to be measured; the flexible piezoresistive pressure sensing unit 1 is installed at the top surface center of the upper plate-like body of the spherical probe 2.

[0064] The main structure of the housing 4 is a thin-walled hollow cylinder. Four protrusions are evenly distributed along the circumference of the top surface for mounting the flexible gated strain sensing unit 3. A rectangular stepped surface is provided along the z-axis along the protrusions to provide a surface for clamping the crossbeam. The bottom of the housing 4 is a frustum, tapering along the outer surface of the cylinder to a flat bottom surface. The center of this flat surface is a through-hole with a radius slightly larger than the indenter of the spherical probe 2. The bottom surface is flush with the lowest point of the indenter. The housing 4 supports the spherical probe 2 and the flexible gated strain sensing unit 3, providing a mounting structure and a stable contact surface.

[0065] like Figure 4 As shown, the spherical probe 2 is made of high modulus hard material. The spherical probe 2 is divided into three sections from top to bottom. The top disc is used to install the flexible piezoresistive pressure sensing unit 1 and bear external loads. The crimping block in the middle section is attached to the square base in the center of the flexible piezoresistive pressure sensing unit 1, and is used to install the spherical probe 2 on the flexible gated strain sensing unit 3 while transmitting positive pressure to it, so that the flexible gated strain sensing unit 3 undergoes vertical axis tensile deformation. The lower section is a cylindrical beam with a hemispherical pressure head. The probe pressure head passes through the central circular hole of the flexible gated strain sensing unit 3. The hemispherical pressure head at the bottom of the spherical probe 2 is flush with the lower plane of the shell 4, and is used to contact the object to be measured and apply positive pressure. The entire spherical probe 2 plays the role of pressing into the object to be measured and transmitting pressure displacement information.

[0066] like Figure 2 As shown, the flexible gated strain sensing unit 3 of the present invention includes a polydimethylsiloxane PDMS packaging film 5, a polydimethylsiloxane PDMS substrate 6 and four fluid resistor microstructures. The polydimethylsiloxane PDMS packaging film 5 and the polydimethylsiloxane PDMS substrate 6 are both cross-beam structures and are provided with concentric second through holes in the center. The top centers of the four cross beams of the polydimethylsiloxane PDMS substrate 6 are provided with mounting grooves. The four fluid resistor microstructures are respectively installed in their respective mounting grooves. The polydimethylsiloxane PDMS packaging film 5 is installed on the top surface of the polydimethylsiloxane PDMS substrate 6 and encapsulates the four fluid resistor microstructures. The crimping block of the spherical probe 2 is When the bottom surface crimping is implemented at the center position of the top surface of the polydimethylsiloxane PDMS packaging film 5, a square base with the same size as the bottom surface of the crimping block is provided in the center of the polydimethylsiloxane PDMS packaging film 5 and the polydimethylsiloxane PDMS substrate 6 to completely contact the bottom surface of the crimping block; conductive metal wires, specifically copper wires, are led out from both ends of each fluid resistor microstructure, one of the conductive metal wires of each fluid resistor microstructure is grounded, and the other conductive metal wire is electrically connected to the voltage divider module 12; the fluid resistor microstructure specifically uses room temperature ionic liquid tetrafluoroborate 1-ethyl-3-methylimidazole [Emim] BF4 solution as the conductive medium in the microchannel.

[0067] The flexible gated strain sensing unit 3 is constructed from flexible PDMS, symmetrically arranged in a cross-shaped pattern along a specific microchannel pattern. It features a square base with a central circular hole of the same diameter as the lower cylindrical portion of the spherical probe 2. This base supports the crimping block that penetrates the hole and measures the displacement of the spherical probe 2 as it is pressed downward. The microchannel structure, when stretched, forms a gating mechanism that blocks electron migration within the conductive solution ([Emim]BF4) within the channel, altering its overall resistivity and enabling highly sensitive strain measurement.

[0068] The central force of the flexible gated strain sensing unit 3 will drive the cross-beam structure to stretch, and the micro-pillars in the microchannel will deform accordingly, reducing the fluid cross-sectional area and increasing the total resistance of the microchannel, thereby converting the vertical axis strain into a voltage signal.

[0069] like Figure 3 (a) and Figure 3 As shown in (b), the flexible piezoresistive pressure sensing unit 1 of the present invention includes a polyimide PI film 7, a piezoresistive sensitive sheet 8 and an interdigital electrode 9. The piezoresistive sensitive sheet 8 is encapsulated between the polyimide PI film 7 and the interdigital electrode 9. The interdigital electrode 9 is provided with two pins. The negative electrode of the interdigital electrode 9 is grounded through one pin, and the positive electrode of the interdigital electrode 9 is electrically connected to the voltage divider module 12 through the other pin. The piezoresistive sensitive sheet 8 specifically uses multi-walled carbon nanotubes MWCNTs (Multi-Walled Carbon Nanotubes) / polydimethylsiloxane PDMS sheet as the force sensitive layer. When an external force is applied to the flexible piezoresistive pressure sensing unit 1, the flexible piezoresistive pressure sensing unit 1, the spherical probe 2 and the flexible gated strain sensing unit 3 move linearly downward in coordination, and the pressure head of the spherical probe 2 presses into the object being measured. The positive pressure acts on the MWCNTs / PDMS piezoresistive sensitive sheet 8, causing the multi-walled carbon nanotubes MWCNTs dispersed in the PDMS to form more conductive paths, thereby changing the conductivity of the sensing unit and converting the positive pressure into an electrical signal.

[0070] The flexible piezoresistive pressure sensing unit 1 uses a MWCNTs / PDMS composite material as the force-sensitive layer. This layer is stacked and encapsulated with flexible interdigitated electrodes 9 using a polyimide (PI) film 7 and tightly adhered to the disc-shaped top surface of a spherical probe 2. This layer measures the pressure applied to the top of the spherical probe 2 during its downward movement. During compression, the multi-walled carbon nanotubes (MWCNTs) dispersed within the flexible polydimethylsiloxane (PDMS) substrate 6 form more conductive paths, altering the conductivity of the flexible piezoresistive pressure sensing unit 1 and enabling highly sensitive pressure measurement.

[0071] like Figure 6As shown, the data acquisition and processing device includes a voltage divider module 12, a voltage acquisition module 11, a data processing module 10, and a host computer module 13, which are connected in sequence. The voltage divider module 12 is electrically connected to the flexible piezoresistive pressure sensing unit 1 and the flexible gated strain sensing unit 3. The voltage divider module 12 is a circuit board with four branches with a resistance of 200kΩ and one branch with a resistance of 1.5kΩ welded on it. A flexible printed circuit (FPC) adapter board is used to achieve a reliable connection between the sensor and the acquisition branch. The voltage acquisition module 11 is specifically a USB_HRF4028 type 16-bit high-precision acquisition card device, the data processing module 10 is specifically an embedded system with an STM32F103R8T6 microcontroller as the control core, and the host computer module 13 is specifically a host computer operating system developed based on Visual Studio. The data processing module 10 processes the collected voltage signal through a specific algorithm, and the host computer module 13 reads and displays the data results.

[0072] The quantitative detection method of the elastic modulus of the dual-mode tactile sensor of the present invention is as follows:

[0073] Step S1: Place the object to be measured horizontally on the loading platform, install the dual-mode tactile sensor directly above the object to be measured, keep the axis of the spherical probe 2 coincident with the normal of the top surface of the object to be measured, make the bottom surface of the shell 4 parallel to the top surface of the object to be measured, and start the data acquisition and processing device.

[0074] Step S2: Stably and uniformly load a uniform positive pressure on the top surface of the spherical probe 2 through the loading surface, so that the loading surface completely covers the flexible piezoresistive pressure sensing unit 1, and push the spherical probe 2 into the object to be measured at a uniform speed. The pressing depth does not exceed the radius of the hemispherical pressure head at the bottom end of the spherical probe 2, and at the same time, the flexible gated strain sensing unit 3 is deformed.

[0075] Step S3: The five-channel voltage signals transmitted by the four fluid resistance microstructures of the flexible piezoresistive pressure sensing unit 1 and the flexible gated strain sensing unit 3 are read through the voltage acquisition single module 11 of the data acquisition and processing device, and then the elastic modulus of the object under test is obtained and displayed after being processed by the elastic modulus quantitative detection algorithm installed in the data acquisition and processing device, thereby realizing quantitative detection of the elastic modulus.

[0076] The voltage divider module 12 of the data acquisition and processing device receives the five-channel voltage signal and transmits it to the data processing module 10 through the voltage acquisition module 11. The elastic modulus quantitative detection algorithm is installed in the data processing module 10. The first step of the elastic modulus quantitative detection algorithm is to first obtain the contact force F between the spherical probe 2 and the object to be measured based on the five-channel voltage signal. i The second step of the elastic modulus quantitative detection algorithm is to calculate the contact force F between the spherical probe 2 and the object to be measured.i The third step of the elastic modulus quantitative detection algorithm is to obtain the elastic modulus of the object to be measured based on the penetration depth δ of the spherical probe 2 into the object to be measured and the Poisson's ratio v of the object to be measured, and transmit it to the host computer module 13 for display.

[0077] In the first step of the elastic modulus quantitative detection algorithm, the loaded uniform positive pressure F is obtained based on the relationship between the voltage signal of the flexible piezoresistive pressure sensing unit 1 and the loaded uniform positive pressure, and then the contact force F between the spherical probe 2 and the object to be measured is obtained. i , as follows:

[0078] F i =F-4F0cosα

[0079] F1=σS=E sensor ε l bt

[0080]

[0081] Among them, F0 is the average value of the force on the four beams of the flexible gated strain sensing unit 3; α is the angle between the flexible gated strain sensing unit 3 and the vertical axis after deformation; F1 is the force along the deformation direction of the flexible gated strain sensing unit 3, and the forces on the four beams are F1, F2, F3, and F4 respectively, and the calculation formulas of the four are similar; σ is the stress along the tensile direction; S is the cross-sectional area of the flexible gated strain sensing unit 3; E sensor is the Young's modulus of the flexible gated strain sensing unit 3; b and t are the width and thickness of the flexible gated strain sensing unit 3, respectively.

[0082] Based on the four-channel voltage signals transmitted by the four fluid resistance microstructures of the flexible gated strain sensing unit 3, the strain ε of the flexible gated strain sensing unit 3 along the stretching direction is obtained. l , and then obtain the penetration depth δ of the spherical probe 2 into the object to be measured. The penetration depth δ of the spherical probe 2 into the object to be measured is equal to the vertical movement distance z of the deformation center of the flexible gated strain sensing unit 3, which is as follows:

[0083]

[0084] Wherein, l is the horizontal length of the flexible gated strain sensing unit 3, ε l is the strain of the flexible gated strain sensing unit 3 along the stretching direction, which is equal to the ratio of the length change of the flexible gated strain sensing unit 3 along the stretching direction to the initial length, and can be calculated according to the strain sensitivity curve.

[0085] In the second step of the elastic modulus quantitative detection algorithm, based on the contact force F between the spherical probe 2 and the object to be measured i As well as the penetration depth δ of the spherical probe 2 into the object to be measured, the correction factor к related to the radius R of the hemispherical indenter at the bottom end of the spherical probe 2, the thickness H of the object to be measured, the Poisson's ratio v of the object to be measured, and the penetration depth δ of the spherical probe 2 into the object to be measured is established by finite element simulation software using Hertz contact theory and finite element analysis method, as follows:

[0086]

[0087]

[0088] Among them, F Y and F H are the contact forces F between the spherical probe 2 and the object to be measured. i Finite element solution and Hertz solution of .

[0089] The correction factor к is optimized by the finite element analysis method to obtain the optimized correction factor к′, which is as follows:

[0090]

[0091] Here, β is the β factor related to the Poisson's ratio v of the object to be measured and the penetration depth δ of the spherical probe 2 into the object to be measured in the finite element analysis method, representing the influence of the Poisson's ratio and large deformation on the contact process.

[0092] Abaqus CAE was used as the finite element simulation software to simulate the probe indenter size of the present invention. A dimensionless analysis was performed for different Poisson's ratios, elastic moduli, thicknesses of the object to be measured, and indentation depths. By fitting the к-δ / H curve, the correction factor к was further expressed as an expression containing the β factor.

[0093] The contact force F between the spherical probe 2 and the object to be measured is adjusted using the optimized correction factor к′. i Make corrections as follows:

[0094] F i ′=(c+cβ*δ / H)δ 3 / 2

[0095]

[0096] Among them, F i ′ is the corrected contact force between the objects to be measured; c is the intercept; E is the elastic modulus of the object to be measured in the finite element analysis, which is obtained by the elastic modulus E of the hemispherical indenter of the spherical probe 2. 11 and the elastic modulus E′ of the object to be measured.

[0097] Establish F i ′ / δ 3 / 2 -δ / H curve, based on the corrected contact force F between the objects to be measured i The linear relationship between the Poisson's ratio v and the β factor of the object to be measured is extracted from the relationship curve of ′, and the Poisson's ratio v of the object to be measured is obtained after interpolation.

[0098] In the third step of the elastic modulus quantitative detection algorithm, the elastic modulus E′ of the object to be tested in the indentation experiment is as follows:

[0099]

[0100] Among them, F i ' is the corrected contact force between the objects to be measured; R1 is the curvature radius of the indenter.

[0101] According to the Hertz contact formula, the elastic modulus and contact force F are established i The relationship between ′ and the indentation depth δ. By considering the indenter as a rigid sphere and the object to be measured as a plane, the Hertz contact formula is simplified and the calculation formula of the elastic modulus is derived.

[0102] The dual-mode tactile sensor used in this invention combines the advantages of nanoindentation theory and Hertz contact theory to measure the elastic modulus of an object. The force-displacement curve measured by the hemispherical indenter and sensor is used to measure the Poisson's ratio of the object under test using a linear equation for the Poisson's ratio v-β factor solved using the finite element method. The elastic modulus of the material is then inversely calculated using the Hertz contact formula, achieving precise and quantitative elastic modulus measurement.

[0103] In specific implementation, the quantitative detection of elastic modulus is achieved through the data processing module 11 of the data acquisition and processing device as follows:

[0104] From the moment the spherical probe 2 contacts the surface of the object being measured, the voltage divider module 12 and the voltage acquisition module 11 begin to continuously read the voltage signals of strain and pressure. Figure 7 As shown in the figure, at the end of the pressing stroke, the distance difference between the two ends of the flexible gated strain sensing unit 3 of the cross-beam structure in the vertical axis direction can be obtained through the tensile deformation of the flexible gated strain sensing unit 3. Since the bottom of the shell 4 structure is always in contact with the surface of the object being measured, the difference in the distance between the two in the vertical axis direction is the pressing depth, which is equal to the deformation of the flexible gated strain sensing unit 3 in the vertical axis direction. The strain of the flexible gated strain sensing unit 3 along the tensile direction is recorded as ε l , the distance difference in the vertical axis direction is recorded as z.

[0105] During the insertion process of the spherical probe 2, the total force applied from the top is balanced by the resistance of the surface of the object being measured to the spherical probe 2 and the component force of the flexible gated strain sensing unit 3 in the vertical axis direction. The contact force can be obtained by subtracting the component force of the flexible gated strain sensing unit 3 in the vertical axis direction from the resultant force.

[0106] The voltage signal of the voltage acquisition module of the dual-mode sensor can be converted into a pressure-displacement curve.

[0107] Then, the Poisson’s ratio of the material under test is measured according to the pressure-displacement curve. Figure 12 (a) Figure 12 (b) Figure 12 (c) and Figure 12 As shown in (d), H2, H3, H4, and H5 represent the objects with thicknesses of 20 mm, 30 mm, 40 mm, and 50 mm in the finite element analysis, and the Poisson's ratio v is set in the range of 0.3 to 3. The linear relationship between the correction factor к and the dimensionless indentation depth δ / H of the object under different thicknesses and Poisson's ratios can be obtained.

[0108] like Figure 13 (a) Figure 13 (b) Figure 13 (c) and Figure 13 As shown in (d), the synthesis can establish F i ′ / δ 3 / 2 -δ / H curve, the ratio of the slope to the intercept of the dimensionless indentation depth δ / H is the β factor.

[0109] like Figure 14 (a) Figure 14 (b) Figure 14 (c) and Figure 14 As shown in (d), after a large number of finite element simulations and analyses, it is found that the Poisson's ratio v is estimated to be independent of the elastic modulus E of the object to be measured. Therefore, a linear relationship between the Poisson's ratio ν and the β factor can be established, and the Poisson's ratio v can be obtained by interpolation for materials with different elastic moduli.

[0110] Finally, according to the Hertz contact formula, the relationship between the elastic modulus, contact force, and indentation depth δ is established. To simplify the expression of the Hertz contact formula, the indenter is regarded as a rigid sphere and the sample as a plane. The simplification process is as follows:

[0111] Contact radius a and contact force F in Hertz theory i The relationship is as follows:

[0112]

[0113] Among them, R iThe combined curvature radius is composed of the curvature radius R1 of the hemispherical indenter of the spherical probe 2 and the curvature radius R2 of the object to be measured, as follows:

[0114]

[0115] Wherein, ν1 is the Poisson's ratio of the hemispherical indenter of the spherical probe 2, and ν2 is the Poisson's ratio of the object to be measured.

[0116] Assuming that the hemispherical indenter is rigid relative to all the samples to be tested, the elastic modulus E of the hemispherical indenter can be considered to be 11 >>The elastic modulus E' of the object to be measured, considering the contact between a rigid sphere and a flat object to be measured, can be simplified as follows:

[0117]

[0118] R i =R1

[0119] At the same time, the contact radius is related to the indentation depth and the indenter radius, which can be expressed as:

[0120]

[0121] Finally, the elastic modulus of the sample can be obtained.

[0122] Combining the pressure and strain signals measured by the dual-mode sensor, the contact force, penetration depth and Poisson's ratio can be calculated. Given the known indenter radius, the elastic modulus of the object being measured can be quantitatively calculated.

[0123] The test process performed during the specific implementation of the present invention is as follows:

[0124] a) Performance test of the flexible piezoresistive pressure sensing unit 1:

[0125] Sensitivity is a core parameter that characterizes sensor performance. It is defined as the ratio of the change in the output signal to the change in the input physical quantity, and directly reflects the system's conversion efficiency to external mechanical stimuli. The present invention uses a universal tensile testing machine as a force loading platform to apply a positive pressure of 0.1 to 15N to the MWCNTs / PDMS piezoresistive sensitive sheet 8 of the flexible piezoresistive pressure sensing unit 1, and uses a semiconductor data analyzer 4200-SCS to measure the output current value of the MWCNTs / PDMS piezoresistive sensitive sheet 8 under different pressures. Based on the current change generated by the sensor when a load is applied, the sensitivity S is as follows:

[0126]

[0127] Wherein, I is the current value when the flexible piezoresistive pressure sensing unit 1 is loaded; I0 is the initial current value when no load is applied to the flexible piezoresistive pressure sensing unit 1; P is the instantaneous pressure value on the surface of the flexible piezoresistive pressure sensing unit 1; F load A is the load applied by the testing machine; contact is the actual contact area between the testing machine pressure head and the flexible piezoresistive pressure sensing unit 1.

[0128] In summary, the 4200-SCS semiconductor parameter analyzer was used to collect the current response data of the flexible piezoresistive pressure sensing unit 1 under different pressure loads. After data processing, the following Figure 8 The pressure-current characteristic curve shown in (a) can be divided into three sensitivity intervals. The results show that the sensitivity of the flexible piezoresistive pressure sensing unit 1 is 0.161 kPa under 0 kPa-100 kPa. -1 , linearity is 0.99; sensitivity is 0.067kPa at 100kPa-150kPa -1 , linearity is 0.99; at 150kPa-300kPa, sensitivity is 0.016kPa -1 , the linearity is 0.99.

[0129] Response time is an important parameter for evaluating the dynamic performance of a sensor, and it characterizes the time interval required for the sensor to output a stable signal after being stimulated by an external stimulus. Cyclic stability reflects the ability of the sensor to maintain its performance stability and output signal without significant degradation or drift during repeated loading and unloading of pressure. The present invention uses a universal testing machine as a mechanical loading device, and the specific test parameters are set as follows: the initial preload is 1N, the loading speed is 1mm / s, and the contact area between the force loading pressure head and the flexible piezoresistive pressure sensing unit 1 is 49mm 2 , and collect current signals through 4200-SCS. The output results are as follows Figure 8 As shown in (b), the response time and recovery time of the MWCNTs / PDMS piezoresistive sensitive sheet 8 of the flexible piezoresistive pressure sensing unit 1 are respectively shown. The response time of the MWCNTs / PDMS piezoresistive sensitive sheet 8 is 76ms, and the recovery time is 101ms, which fully demonstrates the excellent response characteristics of the MWCNTs / PDMS as the piezoresistive sensitive sheet 8 to external stimuli under uniaxial load loading. Subsequently, 1200 cycles of loading were performed under a pressure of 5N to test its mechanical stability. The test results are shown in FIG. Figure 8 As shown in (c), the MWCNTs / PDMS piezoresistive sensitive sheet 8 exhibits excellent mechanical stability under cyclic loading and can meet the needs of practical applications.

[0130] b) Performance test of flexible gated strain sensing unit 3:

[0131] The minimum strain value that the flexible gated strain sensing unit 3 can detect under external stimulation is called the lower limit of measurement or the minimum detection limit. The minimum detection limit of the flexible gated strain sensing unit 3 of the present invention is related to the minimum detection limit of the indentation depth. The sensitivity factor GF (Gauge Factor) value of the flexible gated strain sensing unit 3 is an important parameter for measuring the response ability of the flexible gated strain sensing unit 3 to strain (deformation). It represents the proportional relationship between the resistance change of the flexible gated strain sensing unit 3 and the mechanical strain it is subjected to. The larger the sensitivity factor GF value, the more sensitive the flexible gated strain sensing unit 3 is to strain.

[0132] In order to facilitate the detection of the performance of the flexible gated strain sensing unit 3, a single pattern on a silicon wafer is molded into a flexible gated strain sensing unit 3, and the measurement lower limit and sensitivity of the flexible strain sensing unit are detected. The detection results are as follows: Figure 9 (a) and Figure 9 As shown in (b), the flexible gated strain sensing unit 3 prepared by the present invention exhibits excellent performance indicators: its strain detection limit can reach 0.04%, the sensitivity coefficient GF value reaches 4.79, and the input-output characteristic curve has a very high linear correlation (R 2 >0.999). These test results fully prove that the sensor meets the technical requirements of practical applications.

[0133] c) Force and displacement calibration of dual-mode sensors:

[0134] The contact force of the dual-mode sensor of the present invention is measured by analyzing the electromechanical response of the flexible piezoresistive pressure sensing unit 1 and the flexible gated strain sensing unit 3. The contact force generated by the spherical probe 2 during the pressing process can be obtained by subtracting the resistance of the flexible gated strain sensing unit 3 to the pressing process of the spherical probe 2 from the load acting on the flexible piezoresistive pressure sensing unit 1. Figure 7 As shown in the figure, at the end of the pressing stroke, the distance difference between the two ends of the flexible gated strain sensing unit 3 of the cross-beam structure in the vertical axis direction can be obtained through the tensile deformation of the flexible gated strain sensing unit 3. Since the bottom of the shell 4 structure is always in contact with the surface of the object being measured, the difference in the distance between the two in the vertical axis direction is the pressing depth, which is equal to the deformation of the flexible gated strain sensing unit 3 in the vertical axis direction. The strain of the flexible gated strain sensing unit 3 along the tensile direction is recorded as ε l .

[0135] Before calibrating the dual-mode sensor, a calibration platform is first built. The sensor is fixed on a universal testing machine. Silicone is placed on the bottom of the sensor to withstand the pressure of the spherical probe 2. The voltage acquisition module 11 and the pressure divider module 12 are connected to the flexible piezoresistive pressure sensing unit 1. First, calibrate the pressure sensing unit. Use the universal testing machine as a static force loading device. Each pressure needs to be maintained for at least three seconds. After the pressure is unloaded, it is necessary to wait for at least three seconds before applying a new pressure. The pressure provided in the vertical direction is divided into 15 values. The calibration range is 0.1-15N. The results are as follows: Figure 10 As shown in (a), △I is the change in current in the dual-mode sensor calibration experiment. Then the flexible gated strain sensing unit 3 was calibrated, using a universal testing machine as the displacement loading device, loading at a rate of 5mm / min, and the end condition was a vertical displacement of 1mm. The tensile modulus of the flexible gated strain sensing unit 3 in the withdrawal experiment was 2.076MPa. Combining its size and material mechanical properties, the strain-resistance change rate curve was converted into a load-resistance change rate curve. The test results are shown as follows: Figure 10 As shown in (b).

[0136] Then, the displacement calibration of the dual-mode sensor is performed. The value of the indentation depth is equal to the displacement component of the flexible gated strain sensing unit 3 in the vertical axis direction of the probe. Its value can be obtained by analyzing the change in the electrical signal of the flexible gated strain sensing unit 3. The indentation depth calibration of the dual-mode sensor is performed using a universal tensile testing machine as a displacement loading platform. A displacement of 1mm is applied along the vertical axis. The resistance change rate of the flexible gated strain sensing unit 3 under 1mm indentation is collected using the voltage acquisition module 11. Figure 11 As shown in the figure, the four sensing units on the cross beam structure of the flexible gated strain sensing unit 3 can be equivalent to four resistors, represented by Y1, Y2, Y3, and Y4 respectively. Their displacement-resistance change rate curves have good consistency, indicating that the displacement of the four beams is very uniform; then the displacement is applied starting from 0.3mm, and the displacement is loaded every 0.1mm until 1mm. According to Figure 11 The resistance change rate can be used to obtain the displacement value output by the flexible gated strain sensing unit 3, where △R is the change in resistance value during the displacement loading experiment.

[0137] d) Quantitative detection of elastic modulus based on dual-mode sensor:

[0138] In order to verify the accuracy of the elastic modulus test, a standard cylindrical test object with a PDMS to curing agent ratio of 10:1, 15:1, and 20:1 was selected, with a radius of 4 cm and a height of 4 cm. A uniaxial compression test was performed on the test object using a universal testing machine to obtain the stress-strain curve, and the elastic modulus value was obtained by analyzing the stress-strain curve. The Poisson's ratio v of the samples with different ratios was analyzed using DIC (Digital Image Correlation) digital image technology to obtain the DIC test value. In addition, Abaqus CAE software was used to perform finite element analysis under the same size to obtain the pressure-displacement curve under the finite element analysis, and the correction factors к and F were obtained by fitting. i ′ / δ 3 / 2 -δ / H curve and Poisson's ratio v-β factor curve, such as Figure 12 、 Figure 13 and Figure 14 shown.

[0139] First, verify the accuracy of the estimated Poisson's ratio v under finite element analysis, and bring the pressure displacement curve obtained by finite element analysis into the calculation model to obtain the following: Figure 15 (a) shows the F of three objects to be tested i ′ / δ 3 / 2 -δ / H relationship curve, the Poisson's ratio of the three is estimated by interpolation, and the accuracy is as follows Figure 15 As shown in (b), the accuracy rate exceeds 95%.

[0140] Then, the accuracy of estimating the Poisson's ratio v in the experiment is verified using a dual-mode sensor. The actual pressure-displacement curve of the object to be measured is obtained according to the above steps. After being brought into the calculation model, the distribution of the β factor in the Poisson's ratio v-β factor curve in the experiment is obtained, as shown in the figure. Figure 16 As shown in (a). The Poisson equation for estimating the dual-mode sensor measurement is obtained by interpolation. Figure 16 As shown in (b), the average accuracy rate reaches over 91%.

[0141] Finally, the elastic modulus value calculated after measuring the Poisson's ratio is output by the host computer module 13 of the data acquisition and processing device, as shown in FIG. Figure 17 As shown in (a), it is found that the average accuracy of the method of the present invention is 91.4% compared with the uniaxial tensile test. Figure 17 As shown in (b), the elastic modulus obtained from the uniaxial tensile test is used as the standard value. The accuracy of the elastic modulus is compared between measuring the Poisson's ratio and assuming the Poisson's ratio. It can be seen that the accuracy of the elastic modulus measurement is improved by 10.3% after measuring the Poisson's ratio.

[0142] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A dual-mode tactile sensor capable of realizing quantitative detection of elastic modulus, characterized in that: include: Housing (4); A flexible gated strain sensing unit (3) is mounted on the top surface of the housing (4) and is used to detect a voltage signal generated when the unit is deformed; The spherical probe (2) is crimped and installed just above the flexible gated strain sensing unit (3), and the lower end is sequentially inserted through the center of the flexible gated strain sensing unit (3) and the housing (4) and contacts the surface of the object to be measured below. When the spherical probe (2) is pressed downward, the flexible gated strain sensing unit (3) is deformed. A flexible piezoresistive pressure sensing unit (1) is mounted on the top surface of the spherical probe (2) and is used to detect a voltage signal generated when the flexible piezoresistive pressure sensing unit is subjected to an external load; The data acquisition and processing device is electrically connected to the flexible piezoresistive pressure sensing unit (1) and the flexible gated strain sensing unit (3) and is used for obtaining the elastic modulus of the measured object by detecting the received voltage signal.

2. The dual-mode tactile sensor capable of realizing quantitative detection of elastic modulus according to claim 1, characterized in that: The shell (4) is in the shape of a hollow cylinder with a through top, the bottom of the shell (4) is in the shape of a through hollow inverted cone, and the center of the bottom surface of the shell (4) is a first through hole; the flexible gated strain sensing unit (3) is a cross beam structure and a second through hole with the same size as the first through hole is opened in the center, and the bottom surfaces of the four cross beam ends of the flexible gated strain sensing unit (3) are crimped to the edge of the top surface of the shell (4); the upper part of the spherical probe (2) is a horizontal plate-like body, the middle part of which is provided with a crimping block, the lower part is a vertical cylindrical body and the bottom end is hemispherical, the top surface of the crimping block and the bottom center of the upper plate-like body of the spherical probe (2) are integrally formed, and the bottom center of the crimping block and The top of the lower cylindrical body of the spherical probe (2) is integrally formed; in an initial state, the flexible gated strain sensing unit (3) is in an undeformed state, the bottom surface of the crimping block of the spherical probe (2) contacts the center of the top surface of the flexible gated strain sensing unit (3), the lower cylindrical body of the spherical probe (2) is sleeved in the first through hole and the second through hole, and the bottom end of the spherical probe (2) is located inside the first through hole and tangent to the center of the outer bottom surface of the shell (4), and the bottom end of the spherical probe (2) and the center of the outer bottom surface of the shell (4) jointly contact the surface of the object to be measured; the flexible piezoresistive pressure sensing unit (1) is installed at the center of the top surface of the upper plate-shaped body of the spherical probe (2).

3. The dual-mode tactile sensor capable of realizing quantitative detection of elastic modulus according to claim 2, characterized in that: The data acquisition and processing device comprises a voltage dividing module (12), a voltage acquisition module (11), a data processing module (10) and a host computer module (13) connected in sequence, wherein the voltage dividing module (12) is electrically connected to a flexible piezoresistive pressure sensing unit (1) and a flexible gated strain sensing unit (3).

4. The dual-mode tactile sensor capable of realizing quantitative detection of elastic modulus according to claim 3, characterized in that: The flexible gated strain sensing unit (3) comprises a polydimethylsiloxane (PDMS) packaging film (5), a polydimethylsiloxane (PDMS) substrate (6) and four fluid resistor microstructures. The polydimethylsiloxane (PDMS) packaging film (5) and the polydimethylsiloxane (PDMS) substrate (6) are both cross-beam structures and are provided with concentric second through holes at their centers. The top centers of the four cross beams of the polydimethylsiloxane (PDMS) substrate (6) are provided with mounting grooves. The four fluid resistor microstructures are respectively installed in their respective mounting grooves. The polydimethylsiloxane (PDMS) packaging film (5) is installed on the top surface of the polydimethylsiloxane (PDMS) substrate (6) and encapsulates the four fluid resistor microstructures. The bottom surface of the crimping block of the spherical probe (2) is crimped to the center position of the top surface of the polydimethylsiloxane (PDMS) packaging film (5). Conductive metal wires are respectively led out from both ends of each fluid resistor microstructure. One of the conductive metal wires of each fluid resistor microstructure is grounded, and the other conductive metal wire is electrically connected to the voltage divider module (12).

5. The dual-mode tactile sensor capable of realizing quantitative detection of elastic modulus according to claim 3, characterized in that: The flexible piezoresistive pressure sensing unit (1) comprises a polyimide PI film (7), a piezoresistive sensitive sheet (8) and an interdigital electrode (9). The piezoresistive sensitive sheet (8) is encapsulated between the polyimide PI film (7) and the interdigital electrode (9). The interdigital electrode (9) is provided with two pins. The negative electrode of the interdigital electrode (9) is grounded via one pin, and the positive electrode of the interdigital electrode (9) is electrically connected to a voltage divider module (12) via the other pin.

6. The method for quantitatively detecting the elastic modulus of a dual-mode tactile sensor according to any one of claims 1 to 5, characterized in that: include: Step S1: placing the object to be measured on the loading platform, installing the dual-mode tactile sensor directly above the object to be measured, keeping the axis of the spherical probe (2) coincident with the normal of the top surface of the object to be measured, bringing the bottom surface of the housing (4) into parallel contact with the top surface of the object to be measured, and starting the data acquisition and processing device; Step S2: uniformly loading a uniformly distributed positive pressure on the top surface of the spherical probe (2) through the loading surface, so that the loading surface completely covers the flexible piezoresistive pressure sensing unit (1), pushing the spherical probe (2) into the object to be measured at a uniform speed, and the pressing depth does not exceed the radius of the hemispherical pressure head at the bottom end of the spherical probe (2), and at the same time, the flexible gated strain sensing unit (3) is deformed; Step S3: The five-channel voltage signals transmitted by the four fluid resistance microstructures of the flexible piezoresistive pressure sensing unit (1) and the flexible gated strain sensing unit (3) are read by the voltage acquisition single module (11) of the data acquisition and processing device, and then the elastic modulus of the object to be measured is obtained and displayed after being processed by the elastic modulus quantitative detection algorithm installed in the data acquisition and processing device, thereby realizing the quantitative detection of the elastic modulus.

7. The method for quantitatively detecting the elastic modulus of a dual-mode tactile sensor according to claim 6, wherein: In step S3, the voltage divider module (12) of the data acquisition and processing device receives the five-channel voltage signal and transmits it to the data processing module (10) through the voltage acquisition module (11). The elastic modulus quantitative detection algorithm is installed in the data processing module (10). The first step of the elastic modulus quantitative detection algorithm is to first obtain the contact force F between the spherical probe (2) and the object to be measured based on the five-channel voltage signal. i and the indentation depth δ of the spherical probe (2) into the object to be measured; the second step of the elastic modulus quantitative detection algorithm is to determine the contact force F between the spherical probe (2) and the object to be measured based on the contact force F between the spherical probe (2) and the object to be measured. i and the penetration depth δ of the spherical probe (2) into the object to be measured, and the Poisson's ratio v of the object to be measured is obtained by combining the Hertz contact theory and the finite element analysis method; The third step of the elastic modulus quantitative detection algorithm is to obtain the elastic modulus of the object to be tested based on the indentation depth δ of the spherical probe (2) into the object to be tested and the Poisson's ratio v of the object to be tested and transmit it to the host computer module (13) for display.

8. The method for quantitatively detecting the elastic modulus of a dual-mode tactile sensor according to claim 7, wherein: In the first step of the elastic modulus quantitative detection algorithm, the loaded uniform positive pressure F is obtained based on the relationship between the voltage signal of the flexible piezoresistive pressure sensing unit (1) and the loaded uniform positive pressure, and then the contact force F between the spherical probe (2) and the object to be measured is obtained. i , as follows: F i =F-4F0 cosα Wherein, F0 is the average value of the forces on the four beams of the flexible gated strain sensing unit (3); α is the angle between the flexible gated strain sensing unit (3) and the vertical axis after deformation; Based on the four-channel voltage signals transmitted by the four fluid resistance microstructures of the flexible gated strain sensing unit (3), the strain ε of the flexible gated strain sensing unit (3) along the stretching direction is obtained. l , and then obtain the indentation depth δ of the spherical probe (2) into the object to be measured, which is equal to the moving distance z of the deformation center of the flexible gated strain sensing unit (3) along the vertical direction, as follows: Wherein, l is the horizontal length of the flexible gated strain sensing unit (3), ε l It is the strain of the flexible gate-controlled strain sensing unit (3) along the stretching direction.

9. The method for quantitatively detecting the elastic modulus of a dual-mode tactile sensor according to claim 7, wherein: In the second step of the elastic modulus quantitative detection algorithm, based on the contact force F between the spherical probe (2) and the object to be measured i and the indentation depth δ of the spherical probe (2) into the object to be measured, the Hertz contact theory and the finite element analysis method are used to establish a correction factor к related to the radius R of the hemispherical indenter at the bottom end of the spherical probe (2), the thickness H of the object to be measured, the Poisson's ratio v of the object to be measured, and the indentation depth δ of the spherical probe (2) into the object to be measured, as follows: Among them, F Y and F H are the contact force F between the spherical probe (2) and the object to be measured i Finite element solution and Hertz solution of ; The correction factor к is optimized by the finite element analysis method to obtain the optimized correction factor к′, which is as follows: Wherein, β is a β factor related to the Poisson's ratio v of the object to be measured and the indentation depth δ of the spherical probe (2) into the object to be measured in the finite element analysis method; The contact force F between the spherical probe (2) and the object to be measured is adjusted using the optimized correction factor к′. i Make corrections as follows: F i ′=(c+cβ*δ / H)δ 3 / 2 Among them, F i ' is the corrected contact force between the objects to be measured; c is the intercept; E is the elastic modulus of the object to be measured in the finite element analysis, which is obtained by the elastic modulus E of the hemispherical indenter of the spherical probe (2) 11 and the elastic modulus E′ of the object to be measured; Based on the corrected contact force F between the objects to be measured i The linear relationship between the Poisson's ratio v and the β factor of the object to be measured is extracted from the relationship curve of ′, and the Poisson's ratio v of the object to be measured is obtained after interpolation.

10. The method for quantitatively detecting the elastic modulus of a dual-mode tactile sensor according to claim 7, wherein: In the third step of the elastic modulus quantitative detection algorithm, the elastic modulus E′ of the object to be measured is as follows: Among them, F i ' is the corrected contact force between the objects to be measured; R1 is the curvature radius of the indenter.

Images