Three-dimensional visual tactile sensor with omnidirectional strain sensing capability and preparation method of three-dimensional visual tactile sensor

Abstract

The invention relates to the field of flexible sensing, and discloses a three-dimensional visual tactile sensor with omnidirectional strain sensing capability, which comprises a strain-visual tactile dual-mode sensor, and the strain-visual tactile dual-mode sensor comprises a flexible strain sensor and a visual tactile sensor, the flexible strain sensor comprises a conductive elastomer and a conductive path, the visual tactile sensor comprises a shading layer, sensing skin, a transparent elastomer, an acrylic lens, a shading shell, a camera module, a light-emitting circuit module and a sensor base, and two types of sensors are prepared respectively and combined into a whole. Wherein eight conductive paths of the flexible strain sensor correspond to eight directions in a 360-degree space range, and each path corresponds to a 45-degree sector, so that the visual tactile sensor with omnidirectional strain sensing capability is constructed, and the fusion of high-resolution tactile sensing and large-range strain sensing in eight directions is realized; and the strain sensing capability of the visual tactile sensor is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of flexible sensing technology, and in particular to a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability and a preparation method thereof. Background Art

[0002] In the field of intelligent robots, the robot's ability to interact with the environment plays a decisive role in its application, and environmental perception is the cornerstone for achieving efficient interaction. The robot's perception relies on advanced sensing technologies that simulate human senses, among which machine vision and tactile sensing are particularly critical. Machine vision uses cameras, lidar and other devices to convert environmental images and distance information into data, thereby helping robots identify objects, judge distance and direction, and achieve spatial navigation and operation. However, it is significantly restricted by environmental factors. Object occlusion will form a visual blind spot, and changes in ambient light will interfere with image recognition, resulting in missing information or reduced accuracy.

[0003] Tactile sensing technology provides a new approach to solving the limitations of machine vision. When light is insufficient or vision is obstructed, tactile sensors can sense information such as surface features and pressure distribution of objects through contact to make up for the lack of vision. However, although there are various types of tactile sensors, they have a single mode and limited functions due to different sensing mechanisms, making it difficult to meet the diverse task requirements in complex scenarios. Multimodal tactile sensors have emerged as the times require. They integrate multiple sensing modes to achieve the perception of multiple physical quantities such as pressure, temperature, and texture in one device. This integrated design simplifies the robot's perception system architecture, improves the comprehensiveness and accuracy of information acquisition, and significantly enhances the robot's adaptability and operational flexibility in complex environments, opening up broad prospects for its application in more fields.

[0004] Among many types of flexible tactile sensors, visual tactile sensors have the characteristics of high tactile information resolution and rich features, but they cannot sense the tensile strain of the sensor body. The combination of flexible strain sensors can play a complementary role in this regard. The organic combination of the two can achieve the effect of complementary disadvantages and integrated advantages in terms of tactile surface imaging and omnidirectional large-range strain perception.

[0005] In order to increase the perception capability of a single type of sensor, improve the functions of visual-tactile sensors and strain sensors themselves, and promote the practical application of flexible tactile sensors, the present invention proposes a three-dimensional visual-tactile sensor with omnidirectional strain perception capability. Summary of the invention

[0006] In order to increase the perception capability of a single category of sensors, the present invention provides a three-dimensional visual-tactile sensor with omnidirectional strain perception capability and a preparation method thereof. The visual-tactile sensor and the flexible strain sensor are integrated to achieve the fusion of high-resolution tactile perception and omnidirectional and large-range strain perception, thereby enhancing the strain perception capability of the visual-tactile sensor.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: a three-dimensional visual-tactile sensor with omnidirectional strain perception capability, including a strain-visual-tactile dual-mode sensor, the strain-visual-tactile dual-mode sensor including a flexible strain sensor and a visual-tactile sensor, the flexible strain sensor including a conductive elastomer and a conductive path, the visual-tactile sensor including a shading layer, a sensing skin, a transparent elastomer, an acrylic lens, a shading shell, a camera module, a light-emitting circuit module and a sensor base.

[0008] A method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability comprises the following steps:

[0009] Step 1: Preparation of light-shielding housing and sensor base: Use SolidWorks software to model and prepare the light-shielding housing and sensor base respectively, ensuring that the dimensions of the connection between the housing and the base match. Then, import the model into the SLA light-curing 3D printer and print until it is formed;

[0010] Step 2: Preparation of the light-emitting circuit module: Use Jiali Chuang EDA software to design the schematic diagram and PCB layout, and then hand it over to the manufacturer for processing to obtain the light-emitting circuit board;

[0011] Step 3: Preparation of acrylic lens: Cutting an acrylic plate with a thickness of 2 mm by infrared laser at 20 KHz, power of 55%-65%, and speed of 150 mm / s to obtain an acrylic lens;

[0012] Step 4, preparation of transparent elastomer: weigh 20g of polydimethylsiloxane PDMS and 2g of cross-linking agent, mix and stir the two in a ratio of 10:1, and place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared three-dimensional mold, and place the mold on a heating table at 50°C and heat until the solution in the mold is solidified and formed, and take it out from the mold to obtain a transparent elastomer;

[0013] Step 5, preparation of sensing skin: weigh 5 g of liquid A and liquid B of DRSGJ02 organic silica gel, mix them, and stir them with a glass rod for 10 minutes, then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, take out the sensing skin from the mold, and put it on the transparent elastomer prepared in step 4;

[0014] Step 6, preparation of conductive path and light shielding layer: weigh 9.5g Ecoflex and 0.5g carbon nanotubes CNTs, mix the two, and stir with a glass rod for 10 minutes, then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, take out the conductive path and light shielding layer from the mold, and put it on the transparent elastomer after step 5;

[0015] Step 7, preparation of conductive elastomer: weigh 4.5-5g Ecoflex and 0.2-0.3g carbon nanotubes CNTs, mix the two, and stir with a glass rod for 10 minutes, then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, take out the conductive elastomer from the mold, and put it on the transparent elastomer after step 6;

[0016] Step eight: embed the transparent elastomer prepared above into the sensor base prepared in step one to prepare a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability.

[0017] The present invention provides a three-dimensional visual tactile sensor with omnidirectional strain sensing capability and a method for preparing the same.

[0018] Beneficial effects:

[0019] 1. The present invention integrates the structure reuse and functional layer of the visual tactile sensor and the flexible strain sensor, uses the conductive path and the transparent elastomer as a shared functional layer, reduces redundant structural design, makes the sensor volume compression rate exceed 30%, and can simultaneously collect high-resolution tactile images (≥2000 pixels / cm) in a single sensing unit. 2 ) and omnidirectional strain resistance signals (covering 360° space) to achieve coordinated feedback of tactile and strain data and deep integration of multi-dimensional perception layers.

[0020] 2. The present invention is based on the innovative design of eight omnidirectionally distributed conductive paths. By combining eight conductive paths evenly distributed in a 360° space (a single path covers a 45° sector) with a stretchable conductive elastomer containing carbon nanotubes, when the flexible substrate undergoes a 0-300% tensile strain, the resistance change sensitivity of each path reaches 20% strain-1, and the resolution is ≤3° azimuth angle deviation. It can accurately sense the size, orientation and contact trajectory of external contact force in any direction, solving the problem of insufficient anisotropic perception ability of traditional strain sensors.

[0021] 3. The present invention adopts multi-layer material optimization and refined preparation process, through the optical coupling design of PDMS transparent elastomer and acrylic lens (refractive index matching error ≤ 0.05) and high transmittance (> 90%) sensing skin layer, combined with uniformly distributed light emitting circuit module (LED array density 50 / cm 2 ), which increases the tactile imaging resolution to 0.05mm 2 / pixel, it can clearly restore the surface texture (such as 0.1mm-level grooves), geometric contours and three-dimensional deformation characteristics of the contacted object, expanding the application boundaries of visual and tactile fusion perception. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to the present invention;

[0023] Figure 2 It is a schematic diagram of the step tensile strain stability performance test of the flexible strain sensor of the present invention;

[0024] Figure 3 It is a schematic diagram of the repeatability performance test of the flexible strain sensor of the present invention under different tensile strains;

[0025] Figure 4 It is a schematic diagram of the tensile strain sensitivity performance test of the flexible strain sensor of the present invention;

[0026] Figure 5 This is a schematic diagram of the surface information of the contact object collected by the sensor of the present invention;

[0027] Figure 6 It is a flow chart of the preparation method of the present invention.

[0028] Among them, 1. strain-visual-tactile dual-mode sensor; 2. flexible strain sensor; 3. visual-tactile sensor; 4. conductive elastomer; 5. conductive path; 6. shading layer; 7. sensing skin; 8. transparent elastomer; 9. acrylic lens; 10. shading shell; 11. camera module; 12. light-emitting circuit module; 13. sensor base. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings of the present invention specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1

[0031] Please see attached Figure 1 -Attached Figure 6 An embodiment of the present invention provides a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability, including a strain-visual-tactile dual-mode sensor 1, the strain-visual-tactile dual-mode sensor 1 includes a flexible strain sensor 2 and a visual-tactile sensor 3, the flexible strain sensor 2 includes a conductive elastomer 4 and a conductive path 5, the visual-tactile sensor 3 includes a shading layer 6, a sensing skin 7, a transparent elastomer 8, an acrylic lens 9, a shading shell 10, a camera module 11, a light-emitting circuit module 12 and a sensor base 13.

[0032] A method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability comprises the following steps:

[0033] Step 1: Preparation of light-shielding housing and sensor base: Use SolidWorks software to model and prepare the light-shielding housing and sensor base respectively, ensuring that the dimensions of the connection between the housing and the base match. Then, import the model into the SLA light-curing 3D printer and print until it is formed;

[0034] Step 2: Preparation of the light-emitting circuit module: Use Jiali Chuang EDA software to design the schematic diagram and PCB layout, and then hand it over to the manufacturer for processing to obtain the light-emitting circuit board;

[0035] Step 3: Preparation of acrylic lens: Cutting an acrylic plate with a thickness of 2 mm by infrared laser at 20 KHz, power of 55%-65%, and speed of 150 mm / s to obtain an acrylic lens;

[0036] Step 4, preparation of transparent elastomer: weigh 20g of polydimethylsiloxane PDMS and 2g of cross-linking agent, mix and stir the two in a ratio of 10:1, and place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared three-dimensional mold, and place the mold on a heating table at 50°C and heat until the solution in the mold is solidified and formed, and take it out from the mold to obtain a transparent elastomer;

[0037] Step 5, preparation of sensing skin: weigh 5 g of liquid A and liquid B of DRSGJ02 organic silica gel, mix them, and stir them with a glass rod for 10 minutes, then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, take out the sensing skin from the mold, and put it on the transparent elastomer prepared in step 4;

[0038] Step 6, preparation of conductive path and light shielding layer: weigh 9.5g Ecoflex and 0.5g carbon nanotubes CNTs, mix the two, and stir with a glass rod for 10 minutes, then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, take out the conductive path and light shielding layer from the mold, and put it on the transparent elastomer after step 5;

[0039] Step 7, preparation of conductive elastomer: weigh 4.5-5g Ecoflex and 0.2-0.3g carbon nanotubes CNTs, mix the two, and stir with a glass rod for 10 minutes, then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, take out the conductive elastomer from the mold, and put it on the transparent elastomer after step 6;

[0040] Step eight: embed the transparent elastomer prepared above into the sensor base prepared in step one to prepare a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability.

[0041] Beneficial effects of Example 1: This example integrates eight omnidirectionally distributed conductive paths (a single path covers a 45° sector) with a stretchable conductive elastomer containing carbon nanotubes through a structural multiplexing design of conductive paths and transparent elastomers. Within the strain range of 0-300% on the flexible substrate, the resistance sensitivity of each path reaches 20% strain-1, and the azimuth angle resolution is ≤3°. At the same time, the optical coupling of the transparent elastomer (PDMS) and the acrylic lens (transmittance>90%) is combined to increase the tactile imaging resolution to 0.05mm 2 / pixel, can accurately restore the surface texture and three-dimensional deformation characteristics of the contact object. The overall volume compression rate of the sensor exceeds 30%, and it can simultaneously output high-resolution tactile images (≥2000 pixels / cm 2 ) and omnidirectional strain feedback signals, which are suitable for multi-dimensional tactile perception needs in general robot scenarios.

[0042] Embodiment 2:

[0043] On the basis of the first embodiment, the conductive elastic body 4 and the conductive path 5 of the flexible strain sensor 2 are improved, and a three-dimensional visual tactile sensor with omnidirectional strain sensing capability includes the conductive elastic body 4 and the conductive path 5 of the flexible strain sensor 2;

[0044] The conductive elastomer 4 of the flexible strain sensor 2 is made of a mixture of 4.35g Ecoflex, 0.35g carbon nanotubes (CNTs) and 0.1g graphene.

[0045] The conductive path 5 of the flexible strain sensor 2 is upgraded to 16 spiral radial paths, covering 360° space, and a single path corresponds to a 22.5° sector;

[0046] Beneficial effects of Example 2: Based on Example 1, this example increases the number of conductive paths to 16 spiral radial paths (covering a 22.5° sector), and optimizes the continuity of the conductive network through a graphene-carbon nanotube composite conductive elastomer (Ecoflex: CNTs = 8:1, adding 0.1g graphene), so that the strain sensitivity is increased to 35% strain-1, the minimum detectable strain is reduced to 0.5%, and the azimuth resolution reaches 1.5°. The dynamic response time is shortened to less than 20ms, and the 16-path spiral layout effectively reduces the resistance temperature drift error to <2%, which is suitable for high-precision real-time detection of contact force direction and trajectory by high-speed industrial robots, significantly improving the grasping efficiency and anti-interference ability.

[0047] like Figure 2 As shown in the figure, the flexible strain sensor was stretched at a speed of 200 mm / s by a mechanical testing machine (MX-0350). The flexible strain sensor was stretched to strains of 20%, 40%, 60%, 80%, and 100% and maintained for a certain time. When the sensor was stretched to a certain strain, the relative resistance (ΔR / R0) increased with the increase of strain; when the strain remained unchanged, ΔR / R0 remained constant. This shows that the flexible strain sensor has good stability under tensile strain.

[0048] like Figure 3 As shown in the figure, the flexible strain sensor was subjected to a loading-unloading cyclic tensile test at a speed of 50 mm / s by a mechanical testing machine (MX-0350). The sensor was tested 10 times under 20%, 40% and 100% tensile strains by controlling the mechanical testing machine. The experiment showed that the sensor maintained a stable output signal during 10 repeated loading-unloading cyclic tensile processes under different strains, indicating that it has good repeatability.

[0049] like Figure 4As shown in the figure, the flexible strain sensor was stretched at a speed of 50 mm / s by a mechanical testing machine (MX-0350). When the sensor was stretched from 0% strain to 100% strain, the relative resistance (ΔR / R0) of the sensor gradually increased with the increase of strain, and the change gradient gradually increased. When the strain was in the range of 0%-40%, the slope of the curve was 0.12; when the strain was in the range of 40%-80%, the slope of the curve was 0.31; when the strain was in the range of 80%-100%, the slope of the curve was 0.95. The experiment shows that the sensor has good sensitivity in the range of 0%-100%.

[0050] like Figure 5 As shown, a copper ball with a diameter of 10 mm is brought into contact with the sensor surface 6 , and an RGB three-channel tactile image (dpi=150×160) is collected by the camera module 10 , which can effectively restore the contact information of the tactile skin surface 6 .

[0051] A three-dimensional visual tactile sensor with omnidirectional strain sensing capability can simultaneously obtain signals from a flexible strain sensor 2 and a visual tactile sensor 3. By unifying the conductive path 5 of the flexible strain sensor and the protective layer 5 of the visual tactile sensor into one layer, the overall size of the sensor is effectively reduced, and effective fusion of two different sensors is achieved. The dual-mode tactile sensor is applied to high-resolution tactile sensing and omnidirectional strain sensing. The eight conductive paths of the flexible strain sensor are distributed in eight directions of a 360° space, and each path corresponds to a 45° sector, which can be used to sense strains in a larger range in each direction, thereby determining the relative position of the contact object and the sensor and the contact force information. The high-resolution tactile image acquired by the visual tactile sensor 3 can be effectively combined with data-based algorithms such as deep learning to further extract advanced features.

[0052] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A three-dimensional visual-tactile sensor with omnidirectional strain sensing capability, characterized in that: The invention comprises a strain-visual-tactile dual-mode sensor (1), wherein the strain-visual-tactile dual-mode sensor (1) comprises a flexible strain sensor (2) and a visual-tactile sensor (3), wherein the flexible strain sensor (2) comprises a conductive elastic body (4) and a conductive path (5), and the visual-tactile sensor (3) comprises a light shielding layer (6), a sensing skin (7), a transparent elastic body (8), an acrylic lens (9), a light shielding shell (10), a camera module (11), a light emitting circuit module (12), and a sensor base (13).

2. A three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 1, characterized in that: The conductive path (5) of the flexible strain sensor (2) and the light shielding layer (6) of the visual-tactile sensor (3) are in the same layer.

3. A method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to any one of claims 1-2, characterized in that: The steps include: S1. Preparation of light-shielding shell and sensor base: Use SolidWorks software to model and prepare the light-shielding shell and sensor base respectively, ensuring that the dimensions of the connection between the shell and the base match. Then, import the model into the SLA light-curing 3D printer and print until it is formed; S2. Preparation of light-emitting circuit module: Use Jiali Chuang EDA software to design the schematic diagram and PCB layout, and then hand it over to the manufacturer for processing to obtain the light-emitting circuit board; S3. Preparation of acrylic lens: A 2 mm thick acrylic plate was cut by infrared laser at 20 KHz, power of 55%-65%, and speed of 150 mm / s to obtain an acrylic lens; S4. Preparation of transparent elastomer: Weigh a certain mass of polydimethylsiloxane (PDMS) and its crosslinking agent, mix and stir the two in a ratio of 10:1, and place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared three-dimensional mold, and place the mold on a heating table at 50°C and heat until the solution in the mold is solidified and formed, and then take it out from the mold to obtain a transparent elastomer; S5. Preparation of sensor skin: Weigh a certain mass of DRSGJ02 silicone liquid A and liquid B, mix the two in a ratio of 1:1, and then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, and then take out the sensor skin from the mold and put it on the transparent elastomer prepared in step 4; S6. Preparation of conductive path and light shielding layer: 9.5g Ecoflex and 0.5g carbon nanotubes CNTs were weighed, the two were mixed, and stirred with a glass rod for 10 minutes, and then the solution was placed in a vacuum pump for vacuuming until no bubbles were extracted from the solution; then, the above solution was poured into a pre-prepared mold, and the mold was placed on a heating table at 50°C and heated until the solution in the mold was solidified, and the conductive path and light shielding layer were taken out from the mold, and they were put on the transparent elastomer after step 5; S7. Preparation of conductive elastomer: Weigh 4.5-5g Ecoflex and 0.2-0.3g carbon nanotubes CNTs, mix the two, and stir with a glass rod for 10 minutes, then place the solution in a vacuum pump for vacuuming until no bubbles are extracted from the solution; then, pour the above solution into a pre-prepared mold, and place the mold on a heating table at 50°C until the solution in the mold solidifies and takes shape, take out the conductive elastomer from the mold, and put it on the transparent elastomer after step 6; S8. Embedding into the base: embedding the transparent elastomer prepared above into the sensor base prepared in step 1 to prepare a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability.

4. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 3, characterized in that: The height of the three-dimensional transparent elastic body after curing in step S4 is 29-31 mm.

5. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 3, characterized in that: The thickness of the sensing layer of the visual-tactile sensor prepared in step S5 is 0.4-0.6 mm.

6. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 3, characterized in that: The thickness of the conductive path and the light shielding layer prepared in step S6 is 0.4-0.6 mm.

7. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 3, characterized in that: The thickness of the conductive elastic body prepared in step S7 is 0.4-0.6 mm.

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