A three-dimensional visual-tactile sensor with omnidirectional strain sensing capability and its preparation method

Abstract

The present application relates to the field of flexible sensing and discloses a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability, including a strain-visual-tactile dual-mode sensor, wherein the strain-visual-tactile dual-mode sensor includes a flexible strain sensor and a visual-tactile sensor, wherein the flexible strain sensor includes a conductive elastomer and a conductive path, and the visual-tactile sensor includes a light-shielding layer, a sensing skin, a transparent elastomer, an acrylic lens, a light-shielding shell, a camera module, a light-emitting circuit module and a sensor base. Two types of sensors are prepared separately and combined into a whole, wherein the eight conductive paths of the flexible strain sensor correspond to eight directions within a 360° spatial range, and each path corresponds to a 45° sector, constructing a visual-tactile sensor with omnidirectional strain sensing capability, realizing the fusion of high-resolution tactile perception and large-scale strain perception in eight directions, and enhancing the strain sensing capability of the visual-tactile sensor.

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 robotics, a robot's ability to interact with its environment plays a decisive role in its application, and environmental perception is the cornerstone of efficient interaction. Robotic perception relies on advanced sensing technologies that mimic human senses, with machine vision and tactile sensing being particularly critical. Machine vision uses devices like cameras and lidar to convert environmental images and distance information into data, enabling robots to identify objects, determine distance and direction, and achieve spatial navigation and manipulation. However, this technology is significantly constrained by environmental factors. Obstructions can create blind spots, and changes in ambient light can interfere with image recognition, leading to missing information or reduced accuracy.

[0003] Tactile sensing technology offers a new approach to addressing the limitations of machine vision. In low light or when vision is obstructed, tactile sensors can compensate for the lack of vision by sensing information such as surface features and pressure distribution through contact. However, while tactile sensors come in a variety of types, their differing sensing mechanisms result in single modes and limited functionality, making them difficult to meet the diverse demands of complex tasks. Multimodal tactile sensors have emerged as a result, integrating multiple sensing modes to enable the perception of multiple physical quantities such as pressure, temperature, and texture in a single device. This integrated design simplifies the architecture of the robot's perception system, 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 even more fields.

[0004] Among the many types of flexible tactile sensors, visual tactile sensors offer high tactile resolution and rich features, but they cannot sense tensile strain within the sensor itself. This is where the integration of flexible strain sensors can complement them. By combining the two, they can achieve a complementary and integrated advantage in both tactile surface imaging and omnidirectional, wide-range strain sensing.

[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-scale 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 sensing 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 light-shielding layer, a sensing skin, a transparent elastomer, an acrylic lens, a light-shielding 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 the light-shielding housing and sensor base: Use SolidWorks software to model and prepare the light-shielding housing and sensor base separately, ensuring that the dimensions of the connection between the housing and the base match. Then, import the model into an SLA light-curing 3D printer and print until it takes shape;

[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: A 2 mm thick acrylic sheet is cut 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 a Transparent Elastomer: Weigh 20g of polydimethylsiloxane (PDMS) and 2g of a cross-linking agent, mix them in a ratio of 10:1, and evacuate the solution using a vacuum pump until no bubbles are removed. Pour the solution into a pre-prepared three-dimensional mold, heat the mold at 50°C, and solidify the solution. Remove the mold to obtain a transparent elastomer.

[0013] Step 5. Preparation of the sensor skin: Weigh 5 g each of DRSGJ02 silicone rubber solution A and solution B, mix them, and stir with a glass rod for 10 minutes. Then, place the solution in a vacuum pump and evacuate it until no bubbles are extracted from the solution. Then, pour the above solution into a pre-prepared mold and heat the mold on a heating table at 50°C until the solution in the mold solidifies. Remove the sensor skin from the mold to obtain a sensor skin and put it on the transparent elastomer prepared in step 4.

[0014] Step 6. Preparation of the Conductive Path and Light-Shielding Layer: 9.5g of Ecoflex and 0.5g of carbon nanotubes (CNTs) were weighed, mixed, and stirred with a glass rod for 10 minutes. The solution was then evacuated using a vacuum pump until no bubbles were extracted. The solution was then poured into a pre-prepared mold and heated on a 50°C heating table until the solution solidified. The conductive path and light-shielding layer were removed from the mold and placed over the transparent elastomer prepared in Step 5.

[0015] Step 7. Preparation of a conductive elastomer: Weigh 4.5-5g of Ecoflex and 0.2-0.3g of carbon nanotubes (CNTs), mix the two, and stir with a glass rod for 10 minutes. Then, evacuate the solution using a vacuum pump until no bubbles are extracted from the solution. Pour the solution into a pre-prepared mold and heat the mold on a heating plate at 50°C until the solution solidifies. Remove the conductive elastomer from the mold to obtain a conductive elastomer, which is then placed over the transparent elastomer prepared in step 6.

[0016] Step 8: Embed 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.

[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 of visual tactile sensor and flexible strain sensor with functional layer, uses conductive path and transparent elastomer as 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 an innovative design of eight omnidirectionally distributed conductive pathways. By combining eight conductive pathways evenly distributed in a 360° space (a single pathway covers a 45° sector) with a stretchable conductive elastomer containing carbon nanotubes, the resistance change sensitivity of each pathway reaches 20% strain-1 when the flexible substrate undergoes a 0-300% tensile strain, with a resolution of ≤3° azimuth angle deviation. It can accurately sense the magnitude, orientation, and contact trajectory of external contact forces in any direction, thus solving the problem of insufficient anisotropic sensing capabilities of traditional strain sensors.

[0021] 3. The present invention adopts multi-layer material optimization and refined preparation technology, through the optical coupling design of PDMS transparent elastomer and acrylic lens (refractive index matching error ≤ 0.05) and high transmittance (> 90%) to sense the skin layer, combined with the 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 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 Schematic diagram of the step tensile strain stability performance test of the flexible strain sensor of the present invention;

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

[0025] Figure 4 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 clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. 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 making creative efforts are within the scope of protection of the present invention.

[0030] Example 1

[0031] Please see the 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 light-shielding layer 6, a sensing skin 7, a transparent elastomer 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.

[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 the light-shielding housing and sensor base: Use SolidWorks software to model and prepare the light-shielding housing and sensor base separately, ensuring that the dimensions of the connection between the housing and the base match. Then, import the model into an SLA light-curing 3D printer and print until it takes shape;

[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: A 2 mm thick acrylic sheet is cut 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 a Transparent Elastomer: Weigh 20g of polydimethylsiloxane (PDMS) and 2g of a cross-linking agent, mix them in a ratio of 10:1, and evacuate the solution using a vacuum pump until no bubbles are removed. Pour the solution into a pre-prepared three-dimensional mold, heat the mold at 50°C, and solidify the solution. Remove the mold to obtain a transparent elastomer.

[0037] Step 5. Preparation of the sensor skin: Weigh 5 g each of DRSGJ02 silicone rubber solution A and solution B, mix them, and stir with a glass rod for 10 minutes. Then, place the solution in a vacuum pump and evacuate it until no bubbles are extracted from the solution. Then, pour the above solution into a pre-prepared mold and heat the mold on a heating table at 50°C until the solution in the mold solidifies. Remove the sensor skin from the mold to obtain a sensor skin and put it on the transparent elastomer prepared in step 4.

[0038] Step 6. Preparation of the Conductive Path and Light-Shielding Layer: 9.5g of Ecoflex and 0.5g of carbon nanotubes (CNTs) were weighed, mixed, and stirred with a glass rod for 10 minutes. The solution was then evacuated using a vacuum pump until no bubbles were extracted. The solution was then poured into a pre-prepared mold and heated on a 50°C heating table until the solution solidified. The conductive path and light-shielding layer were removed from the mold and placed over the transparent elastomer prepared in Step 5.

[0039] Step 7. Preparation of a conductive elastomer: Weigh 4.5-5g of Ecoflex and 0.2-0.3g of carbon nanotubes (CNTs), mix the two, and stir with a glass rod for 10 minutes. Then, evacuate the solution using a vacuum pump until no bubbles are extracted from the solution. Pour the solution into a pre-prepared mold and heat the mold on a heating plate at 50°C until the solution solidifies. Remove the conductive elastomer from the mold to obtain a conductive elastomer, which is then placed over the transparent elastomer prepared in step 6.

[0040] Step 8: Embed 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.

[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] Example 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 to provide a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability, including 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, with a single path corresponding 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, with 0.1g of graphene added). This increases strain sensitivity to 35% strain-1, reduces the minimum detectable strain to 0.5%, and achieves 1.5° azimuth resolution. Dynamic response time is shortened to less than 20ms, and the 16-path spiral layout effectively reduces resistance temperature drift error to <2%. This makes it suitable for high-precision, real-time detection of contact force direction and trajectory by high-speed industrial robots, significantly improving gripping efficiency and anti-interference capabilities.

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

[0048] like Figure 3 As shown in the figure, a flexible strain sensor was subjected to cyclic loading and unloading tensile testing at a speed of 50 mm / s using a mechanical testing machine (MX-0350). The machine was controlled to repeat the test 10 times at tensile strains of 20%, 40%, and 100%. The sensor maintained a stable output signal during the 10 repeated loading and unloading cycles at different strains, demonstrating good repeatability.

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

[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 captured by the camera module 10 . This image 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 perception and omnidirectional strain perception. 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 within a large range in various directions, thereby determining the relative position of the contact object and the sensor and the contact force information. The high-resolution tactile image collected by the visual-tactile sensor 3 can be effectively combined with data-based algorithms such as deep learning to further extract advanced features.

[0052] While 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 these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability, characterized in that: The steps include: S1. Preparation of the light-shielding housing and sensor base: Using SolidWorks software, the light-shielding housing and sensor base were separately modeled, ensuring that the dimensions of the connection between the housing and the base matched. The models were then imported into a SLA (Solid Light-Stage) 3D printer and printed until they were formed. S2. Preparation of the light-emitting circuit module: Schematic design and PCB layout are performed using Jiali Chuang EDA software, and the light-emitting circuit board is then processed by a manufacturer. S3. Preparation of acrylic lens: A 2 mm thick acrylic sheet was cut by infrared laser at 20 kHz, a power of 55%-65%, and a speed of 150 mm / s to obtain an acrylic lens; S4. Preparation of a transparent elastomer: Weigh a certain amount of polydimethylsiloxane (PDMS) and its cross-linker in a ratio of 10:1 and stir. Evacuate the solution using a vacuum pump until no bubbles are removed. Pour the solution into a pre-prepared three-dimensional mold and heat the mold at 50°C until the solution solidifies. Remove the mold to obtain the transparent elastomer. S5. Preparation of the sensor skin: Weigh a certain amount of DRSGJ02 silicone gel solution A and solution B, mix them in a 1:1 ratio, and evacuate the solution using a vacuum pump until no bubbles are removed. Pour the solution into a pre-prepared mold and heat the mold at 50°C until the solution solidifies. Remove the sensor skin from the mold and place it over the transparent elastomer prepared in step 4. S6. Preparation of the conductive path and light-shielding layer: 9.5 g of Ecoflex and 0.5 g of carbon nanotubes (CNTs) were weighed, mixed, and stirred with a glass rod for 10 minutes. The solution was then evacuated using a vacuum pump until no bubbles were removed. The solution was then poured into a pre-prepared mold and heated on a 50°C heating plate until the solution solidified. The conductive path and light-shielding layer were removed from the mold and placed over the transparent elastomer prepared in step 5. S7. Preparation of a conductive elastomer: Weigh 4.5-5g of Ecoflex and 0.2-0.3g of carbon nanotubes (CNTs), mix them, and stir with a glass rod for 10 minutes. Evacuate the solution using a vacuum pump until no bubbles are removed. Pour the solution into a pre-prepared mold and heat the mold at 50°C until the solution solidifies. Remove the conductive elastomer from the mold and place it over the transparent elastomer prepared in step 6. S8. Embedding into the base: embed 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.

2. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 1, characterized in that: The height of the three-dimensional transparent elastic body after curing in step S4 is 29-31 mm.

3. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 1, characterized in that: The thickness of the visual-tactile sensor sensing layer prepared in step S5 is 0.4-0.6 mm.

4. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 1, characterized in that: The thickness of the conductive path and the light shielding layer prepared in step S6 is 0.4-0.6 mm.

5. The method for preparing a three-dimensional visual-tactile sensor with omnidirectional strain sensing capability according to claim 1, characterized in that: The thickness of the conductive elastomer prepared in step S7 is 0.4-0.6 mm.

6. A three-dimensional visual-tactile sensor with omnidirectional strain sensing capability prepared by the preparation method according to claim 1, 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 elastomer (4) and a conductive path (5), and the visual-tactile sensor (3) comprises a light-shielding layer (6), a sensing skin (7), a transparent elastomer (8), an acrylic lens (9), a light-shielding housing (10), a camera module (11), a light-emitting circuit module (12), and a sensor base (13).

7. A three-dimensional visual-tactile sensor with omnidirectional strain sensing capability prepared by the preparation method 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.

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