Distributed touch sensor based on flexible optical waveguide and gradient microstructure and detection method

Abstract

The invention discloses a distributed touch sensor based on a flexible optical waveguide and a gradient microstructure and a detection method, and belongs to the technical field of optical sensors. Double optical waveguides are adopted to output signals, the two optical waveguides are arranged in parallel, optical transmission is restrained through frustrated total internal reflection, the first optical waveguide measures the magnitude of acting force through uniform optical loss characteristics, and a microstructure in contact with an inner core of the second optical waveguide is arranged in an upper wrapping layer of the second optical waveguide. The microstructures are arranged according to the structure size or density gradient, stress position detection and synchronous decoupling of contact force and position information are achieved through the optical loss of the microstructures at different positions and the difference of the first optical waveguide, and the touch sensing device has the advantages of high sensitivity and high resolution and is suitable for touch sensing of intelligent manipulators, soft robots and complex mechanical systems.

Description

Technical Field

[0001] The present invention belongs to the field of sensors, and relates to a distributed flexible tactile sensor based on a flexible optical waveguide and a gradient microstructure and a detection method thereof, which are used for tactile perception of complex mechanical systems, intelligent manipulator applications and the field of soft robots. Background Art

[0002] With the development of robot technology and the deepening of robot application scenarios, the application demand for tactile sensors in the fields of intelligent manipulators, robots and wearable devices is increasing day by day. People hope that robots can intelligently perceive changes in the external environment, especially perceive different degrees of contact pressure and position, so as to better realize intelligent interaction of robots. Currently developed flexible tactile sensors are based on five sensing mechanisms: capacitive, resistive, piezoelectric, optical and triboelectric. However, traditional tactile sensors mostly adopt electrical principles and have certain limitations in terms of flexibility and stability. Optical tactile sensors have gradually attracted attention due to their advantages of anti-electromagnetic interference, high response speed and distributed detection.

[0003] The current optical waveguide-based flexible tactile sensors have problems of uneven sensitivity and insufficient resolution in distributed detection. Preparing an optical waveguide cladding with a microstructure can improve the mechanical transmission characteristics of the sensor, making it have high sensitivity and high pressure resolution.

[0004] Therefore, the present invention proposes a distributed tactile sensor and a detection method based on a flexible optical waveguide and a gradient microstructure to achieve high-sensitivity and high-resolution distributed tactile perception. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a distributed tactile sensor and a detection method based on a flexible optical waveguide and a gradient microstructure to achieve a high-sensitivity response to the acting force and accurate position perception.

[0006] The technical solution adopted by the present invention is as follows: A distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure, the tactile sensor mainly includes: a first optical waveguide 1, a second optical waveguide 4 and an outer cladding 8; Wherein, the first optical waveguide 1 includes a first optical waveguide core 2 and a first optical waveguide cladding 3; the second optical waveguide 4 includes a second optical waveguide core 5, a second optical waveguide lower cladding 6 and a second optical waveguide upper cladding 7; the first optical waveguide core 2 is in the middle of the first optical waveguide cladding 3; the second optical waveguide core 5 is between the second optical waveguide lower cladding 6 and the second optical waveguide upper cladding 7; the first optical waveguide core 2 and the second optical waveguide core 5 are arranged in parallel, and the first optical waveguide 1 and the second optical waveguide 4 are separated by the outer cladding 8; The refractive index of the first optical waveguide core 2 is greater than that of the first optical waveguide cladding 3; the refractive index of the second optical waveguide core 5 is greater than that of the second optical waveguide lower cladding 6 and the second optical waveguide upper cladding 7; to cause frustrated total internal reflection at the interfaces of the first optical waveguide 1 and the second optical waveguide core 5 and cladding. The second optical waveguide upper cladding 7 includes a plurality of microstructures, which are uniformly distributed along the input end to the output end direction, and the microstructures form a plurality of gradients along the input end to the output end direction according to the structural size or structural density of the microstructures, and the microstructures are arranged in parallel and in contact with the second optical waveguide core 5.

[0007] The input end of the first optical waveguide core 2 is connected to a light source through an external standard optical fiber, and the output end of the first waveguide core 2 is connected to a photodetector through an external standard optical fiber; the input end of the second optical waveguide core 5 is connected to a light source through an external standard optical fiber, and the output end of the second optical waveguide core 5 is connected to a photodetector through an external standard optical fiber.

[0008] Preferably, the cross-sections of the first optical waveguide 1 and the second optical waveguide 4 are rectangular as a whole, with the width between 1 - 5 mm and the height between 0.5 - 5 mm; the heights of the first optical waveguide 1 and the second optical waveguide 4 are equal to uniformly sense the external force; the cross-sections of the first optical waveguide core 2 and the second optical waveguide core 5 are rectangular, with the width between 0.05 - 3 mm and the height between 0.02 - 3 mm; the cross-sections of the first optical waveguide cladding 3, the second optical waveguide lower cladding 6, and the second optical waveguide upper cladding 7 are rectangular as a whole, with the length between 30 - 100 mm; the cross-section of the outer cladding 8 is rectangular as a whole, with the rectangular width between 2 - 10 mm and the height between 1 - 10 mm.

[0009] Preferably, the microstructures are convex structures with micron-sized dimensions. Optionally, the convex structures are micro-pyramids, micro-creases, micro-column arrays, and microstructures replicated from plants (such as lotus leaves, roses).

[0010] Preferably, the second optical waveguide upper cladding 7 includes four microstructures with different structural sizes, and the microstructures are uniformly arranged in ascending order of structural size along the input end to the output end direction.

[0011] The present invention also provides a preparation method of a distributed tactile sensor based on a flexible optical waveguide, and the steps of the method are as follows: (1) Prepare the first optical waveguide 1; The materials of the first optical waveguide core 2 and the first optical waveguide cladding 3 are respectively demolded by casting to obtain the preforms of the first optical waveguide core 2 and the first optical waveguide cladding 3; the first optical waveguide core 2 is placed into the groove of the preform of the first optical waveguide cladding 3, and the material of the first optical waveguide cladding 3 is injected again so that the first optical waveguide core 2 is encapsulated in the first optical waveguide cladding 3; the optical refractive index n 芯 of the core material and the optical refractive index n 包 of the cladding material satisfy the condition of frustrated total internal reflection; (2) Prepare the second optical waveguide core 5 and the second optical waveguide lower cladding 6; The material of the second optical waveguide core 5 is placed into the mold C13. After the material is hot-pressed and molded, it is taken out by demolding to obtain the preform of the second optical waveguide core 14; a groove with an interference fit with the preform of the second optical waveguide core 14 is machined on the upper surface of the material of the second optical waveguide lower cladding 6, and the preform of the second optical waveguide core 14 is placed in the groove to obtain the second optical waveguide preform 15; the second optical waveguide preform 15 is prepared by the melt drawing method to obtain the second optical waveguide core and the second optical waveguide lower cladding 6 of the second optical waveguide 4; the optical refractive index n 芯’ of the second optical waveguide core material and the optical refractive index n 包’ of the cladding material satisfy the condition of frustrated total internal reflection; (3) Prepare the micro-structure and the second optical waveguide upper cladding 7; The micro-structure material is respectively cast on the surfaces of sandpapers with different mesh numbers. After the material is cured, the cured film is detached from the sandpaper surface to obtain micro-structures with different structural sizes. The material of the second optical waveguide upper cladding 7 is injected into the mold D, and then the above-mentioned ones are uniformly placed into the mold D in the order of structural size from the input end to the output end. After the material is cured, it is demolded to obtain the second optical waveguide upper cladding 7; the optical refractive index n 芯’ of the second optical waveguide core material and the optical refractive index n 包” of the second optical waveguide upper cladding 7 material satisfy the condition of frustrated total internal reflection; (4) Prepare the second optical waveguide 4; Cover the second optical waveguide upper cladding 7 on the second optical waveguide core 5 so that the micro-structures included in the second optical waveguide upper cladding 7 are arranged in parallel and in contact with the second optical waveguide core 5; the side surfaces are completely encapsulated with the material of the second optical waveguide upper cladding 7 or glue to obtain the second optical waveguide 4; (5) Encapsulation of the distributed tactile sensor based on the flexible optical waveguide; Place the first optical waveguide 1 and the second optical waveguide 4 into the grooves of the mold E. Connect the input standard optical fiber and the output standard optical fiber to the first optical waveguide 1 and the second optical waveguide 4 respectively at both ends of the grooves, so that the core of the first optical waveguide 2 and the core of the second optical waveguide are connected to the standard optical fiber; encapsulate the optical waveguide sensor with the outer cladding 8 material to form a finished optical waveguide sensor.

[0012] The material of the core 2 of the first optical waveguide is PDMS with a first ratio. The PDMS is a two-component silicone rubber, and the first ratio means that the ratio between PDMS and the curing agent is 5:1 by mass; the material of the cladding 3 of the first optical waveguide is PDMS with a second ratio, and the second ratio means that the ratio between PDMS and the curing agent is 10:1 by mass.

[0013] The material of the core of the second optical waveguide is fluorinated acrylic granular material; the material of the lower cladding 6 of the second optical waveguide is PVDF.

[0014] The material of the upper cladding 7 of the second optical waveguide, the microstructure material, and the outer cladding 8 material are PDMS with a second ratio. The second ratio means that the ratio between PDMS and the curing agent is 10:1 by mass.

[0015] The present invention also provides a detection method for a distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure. The specific steps are as follows: (1) Calculate the optical loss of the core 2 of the first optical waveguide according to the input optical intensity at the input end of the core 2 of the first optical waveguide and the optical intensity detected by the optical receiver of the core 2 of the first optical waveguide; similarly, calculate the optical loss of the core of the second optical waveguide according to the input optical intensity at the input end of the core of the second optical waveguide and the optical intensity detected by the optical receiver of the core of the second optical waveguide. (2) Obtain the magnitude of the force on the core 2 of the first optical waveguide according to the fitting relationship between the optical loss of the core 2 of the first optical waveguide and the force. (3) According to a series of fitting relationships between the optical losses at different positions of the core of the second optical waveguide and the force, substitute the magnitude of the force on the core 2 of the first optical waveguide into the series of fitting relationships. When the optical loss is the same as the actual measurement result, it can be determined that deformation occurs at the position corresponding to this relationship, and the force position data is obtained.

[0016] The beneficial effects of the present invention: (1) The present invention uses the reverse molding method, hot pressing method, and melting and drawing method to manufacture a flexible optical tactile sensor. The core and the cladding are manufactured separately and then encapsulated, which has the advantages of good consistency, easy manufacturing, and stable performance.

[0017] (2) Since the present invention adopts an optical waveguide component including microstructures, the microstructures in different parts have different light loss rates. Combining with the method for sensing the output light intensity of the dual-core, it is possible to realize the synchronous and continuous measurement of the contact force and position. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0019] Figure 1 It is a structural diagram of an embodiment of the present invention.

[0020] Figure 2 It is a manufacturing flow chart of the first optical waveguide of an embodiment of the present invention.

[0021] Figure 3 It is a manufacturing flow chart of the second optical waveguide of an embodiment of the present invention.

[0022] Figure 4 It is a relationship diagram of the light intensity and wavelength of the first optical waveguide of an embodiment of the present invention under different pressures.

[0023] Figure 5 It is a relationship diagram of the light intensity and wavelength of the four microstructural regions of the second optical waveguide of an embodiment of the present invention under different pressures.

[0024] Figure 6 It is a relationship diagram of the pressure and light intensity of the four microstructural regions of the second optical waveguide of an embodiment of the present invention when the wavelength is 632 nm.

[0025] Among them, 1 - the first optical waveguide, 2 - the inner core of the first optical waveguide, 3 - the cladding of the first optical waveguide, 4 - the second optical waveguide, 5 - the inner core of the second optical waveguide, 6 - the lower cladding of the second optical waveguide, 7 - the upper cladding of the second optical waveguide, 8 - the outer cladding, 9 - mold A, 10 - forming groove A, 11 - mold B, 12 - forming groove B, 13 - mold C, 14 - preform of the inner core of the second optical waveguide, 15 - preform of the second optical waveguide, 16 - the first microstructure, 17 - the second microstructure, 18 - the third microstructure, 19 - the fourth microstructure. DETAILED DESCRIPTION OF THE INVENTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] In the present invention, terms such as "first" and "second" are used to distinguish different components. It should be noted that there is no logical or temporal dependency between "first" and "second", nor are their quantities and orders restricted. It should also be noted that although the following uses nouns such as first and second to describe each component, these components should not be restricted by the nouns.

[0028] As Figure 1 shown, a distributed tactile sensor based on a flexible optical waveguide in this embodiment mainly includes: a first optical waveguide 1, a second optical waveguide 4, and an outer cladding 8, and the outer cladding 8 completely wraps the first optical waveguide 1 and the second optical waveguide 4; The first optical waveguide 1 and the second optical waveguide 4 are arranged in parallel and separated within the outer cladding 8. In the present invention, the separated arrangement means that the first optical waveguide 1 and the second optical waveguide 4 are separated by the outer cladding 8 to avoid crosstalk of the light transmitted in the first optical waveguide 1 and the second optical waveguide 4; The core 2 of the first optical waveguide is in the middle of the cladding 3 of the first optical waveguide; the input end of the core 2 of the first optical waveguide is connected to a first light source through an externally connected standard optical fiber, and the output end of the core of the first waveguide is connected to a photodetector through an externally connected standard optical fiber; the light emitted by the first light source is received by the first photodetector after passing through the first optical waveguide 1; the core width of the first optical waveguide 1 is uniform, that is, the light loss rate of the acting force is equal along the direction from the input end to the output end.

[0029] The core 5 of the second optical waveguide is between the lower cladding 6 and the upper cladding 7 of the second optical waveguide; the core 2 of the first optical waveguide and the core 5 of the second optical waveguide are arranged in parallel; the input end of the core 5 of the second optical waveguide is connected to a first light source through an externally connected standard optical fiber, and the output end of the core of the second waveguide is connected to a photodetector through an externally connected standard optical fiber; four microstructures are included in the upper cladding 7 of the second optical waveguide, and the microstructures are uniformly arranged in the direction from the input end to the output end according to the decreasing structural size; the core of the second optical waveguide is affected by the microstructures at different positions of the upper cladding, that is, the light loss rate of the acting force is different at different microstructure positions along the direction from the input end to the output end.

[0030] The refractive index of the first optical waveguide core 2 is greater than the outer refractive index of the first optical waveguide cladding 3; the refractive index of the second optical waveguide core 5 is greater than the refractive index of the second optical waveguide lower cladding 6 and the outer refractive index of the second optical waveguide lower cladding 6; so that frustrated total internal reflection occurs at the interface between the first optical waveguide core 2 and the second optical waveguide core 5. The refractive indices of the first optical waveguide core 2 and the second optical waveguide core 5 may be the same or different. This embodiment describes the situation where the refractive indices of the two are different.

[0031] Figure 3 is a cross-sectional view of the lateral direction of a tactile sensor provided by an exemplary embodiment of the present invention. As Figure 3 shown, in this embodiment, the cross-sections of the first optical waveguide 1 and the second optical waveguide are both rectangular as a whole, with a width of 1 mm and a height of 0.5 mm. The cross-sectional heights of the first optical waveguide 1 and the second optical waveguide are equal to uniformly sense the external force; the cross-sectional widths of the first optical waveguide 1 and the second optical waveguide 4 may be the same or different. This embodiment describes the situation where the cross-sectional widths of the two are the same. The cross-section of the first optical waveguide core 2 is square as a whole, with a side length of 0.3 mm. The cross-section of the second optical waveguide core 5 is rectangular, with a width of 0.1 mm and a height of 0.03 mm. In this embodiment, the cross-sectional shapes of the first optical waveguide 1 and the second optical waveguide 4 may also be circular or rectangular, but are not limited to these shapes.

[0032] Figure 4 is a longitudinal cross-sectional view of the microstructure of a tactile sensor provided by an exemplary embodiment of the present invention. As Figure 3 shown, in this embodiment, the lengths of the first optical waveguide 1 and the second optical waveguide 4 are 90 mm; the second optical waveguide upper cladding 7 includes four different microstructures, namely the first microstructure 16, the second microstructure 17, the third microstructure 18, and the fourth microstructure 19; the microstructures are uniformly arranged in the order of the input end to the output end according to the structural size order as: the first microstructure 16 > the second microstructure 17 > the third microstructure 18 > the fourth microstructure 19; the lengths of the four microstructures are 10 mm respectively, and the interval between adjacent microstructures is 10 mm. The microstructures are arranged in parallel and in contact with the second optical waveguide core 5; in this embodiment, the microstructures are made of a dark material to increase the light absorption rate of the total suppression reflection interface, making the light loss amount of the contact force on the second optical waveguide core 5 more significant.

[0033] Figure 5 is a flowchart of a preparation method of a tactile sensor provided according to an embodiment of the present invention. As Figure 5 shown, the method includes the following five steps: (1) Prepare the first optical waveguide 1; Inject the material of the first optical waveguide core 2 and the material of the first optical waveguide cladding 3 into the forming grooves A10 of the mold A9 and the forming grooves B12 of the mold B11 respectively. After the materials are cured, demold and take them out respectively to obtain the preforms of the first optical waveguide core 2 and the first optical waveguide cladding 3. Place the first optical waveguide core 2 into the groove of the preform of the first optical waveguide cladding 3, and inject the material of the first optical waveguide cladding 3 again to encapsulate the first optical waveguide core 2 in the first optical waveguide cladding 3. The optical refractive index n_core of the material of the first optical waveguide core 2 and the optical refractive index n_cladding of the material of the first optical waveguide cladding 3 satisfy the condition of frustrated total internal reflection. (2) Prepare the second optical waveguide core 5 and the second optical waveguide lower cladding 6. Place the material of the second optical waveguide core 5 into the mold C13. After the material is hot-pressed and formed, demold and take it out to obtain the preform of the second optical waveguide core 14. Process the upper surface of the material of the second optical waveguide lower cladding 6 to form a groove with an interference fit with the preform of the second optical waveguide core 14, and place the preform of the second optical waveguide core 14 in the groove to obtain the preform of the second optical waveguide 15. Prepare the second optical waveguide core 5 and the second optical waveguide lower cladding 6 of the second optical waveguide 4 from the preform of the second optical waveguide 15 by the method of melting and drawing. The optical refractive index n_core' of the material of the second optical waveguide core 5 and the optical refractive index n_cladding' of the material of the second optical waveguide lower cladding 6 satisfy the condition of frustrated total internal reflection. (3) Prepare the microstructures and the second optical waveguide upper cladding 7. Cast the microstructure material on the surfaces of four different meshes of sandpaper respectively. After the materials are cured, detach the cured films from the sandpaper surfaces to obtain the first microstructure 16, the second microstructure 17, the third microstructure 18 and the fourth microstructure 19 respectively. Inject the material of the upper cladding 7 of the second optical waveguide 4 into the mold D, and then place the first microstructure 16, the second microstructure 17, the third microstructure 18 and the fourth microstructure 19 into the mold D evenly in the order of the structural dimensions along the input end to the output end direction. After the materials are cured, demold to obtain the upper cladding 7 of the second optical waveguide. The optical refractive index n_core' of the material of the second optical waveguide core 5 and the optical refractive index n_cladding'' of the material of the upper cladding 7 of the second optical waveguide satisfy the condition of frustrated total internal reflection. (4) Prepare the second optical waveguide 4. Cover the upper cladding 7 of the second optical waveguide on the second optical waveguide core 5, so that the microstructures included in the upper cladding 7 of the second optical waveguide are arranged in parallel and in contact with the second optical waveguide core 5. Seal all its sides with the material of the upper cladding 7 of the second optical waveguide or glue to obtain the second optical waveguide 4. (5) Encapsulation of the distributed tactile sensor based on the flexible optical waveguide. Place the first optical waveguide 1 and the second optical waveguide 4 into the groove of mold E. Connect the input standard optical fiber and the output standard optical fiber to the first optical waveguide 1 and the second optical waveguide 4 respectively at both ends of the groove, so that the core 2 of the first optical waveguide and the core 5 of the second optical waveguide are communicated with the standard optical fiber; encapsulate the optical waveguide sensor with the outer cladding 8 material to form a finished optical waveguide sensor.

[0034] In this embodiment, the material of the core 2 of the first optical waveguide is PDMS with a first ratio. The PDMS is a two-component silica gel, and the first ratio means that the ratio between PDMS and the curing agent is 5:1 by mass; the material of the cladding 3 of the first optical waveguide is PDMS with a second ratio, and the second ratio means that the ratio between PDMS and the curing agent is 10:1 by mass; the material of the core 5 of the second optical waveguide is fluorinated acrylic granule material; the material of the lower cladding 6 of the second optical waveguide is PVDF; the material of the upper cladding 7 of the second optical waveguide, the microstructure material and the material of the outer cladding 8 are PDMS with a second ratio, and the second ratio means that the ratio between PDMS and the curing agent is 10:1 by mass; among them, the microstructure material is doped with 3 mg of coloring agent.

[0035] Figure 1 It is a schematic diagram of a distributed tactile perception method based on a flexible optical waveguide provided by an example of the present invention. Since the refractive index of the core layer of the first optical waveguide 1 and the second optical waveguide 4 is greater than the refractive index of the cladding material, light is confined to propagate in the core 2 of the first optical waveguide and the core 5 of the second optical waveguide.

[0036] Since both the cladding and the core of the core of the first optical waveguide are made of flexible materials, when any point on it is externally pressed, it will deform, causing a part of the light in the waveguide core to overflow the core because it does not meet the total reflection condition, resulting in a decrease in the detected light intensity. Because the cross-sectional size of the first optical waveguide 1 is uniformly distributed along the light propagation direction, the response of any position on the first optical waveguide 1 to external pressure is the same, without position dependence, and can only be used to detect the magnitude of pressure.

[0037] Both the second optical waveguide core and the lower cladding are rigid polymers, the upper cladding is a flexible polymer, and the first microstructure 16, the second microstructure 17, the third microstructure 18, and the fourth microstructure 19 discretely distributed on the upper cladding are all flexible materials. When pressure acts on the second optical waveguide 4, it can be divided into two cases: directly acting on the cladding planar structure of the second optical waveguide 4 and acting on the microstructures. When the pressure acts on the planar structure of the upper cladding, since the core and the lower cladding are both rigid materials, they will not deform, and the refractive index change of the planar structure of the upper cladding under pressure is also relatively weak, so no obvious optical loss will be caused. When the pressure acts on the microstructure region, the contact area between the microstructure and the core increases, resulting in obvious scattering loss. Since the microstructure density of the first microstructure 16, the second microstructure 17, the third microstructure 18, and the fourth microstructure 19 changes in a gradient manner, under the same pressure, the optical losses caused by different microstructure regions are different. By comparing the light intensity changes of the first optical waveguide 1, it can be inferred which microstructure region the external pressure acts on. Based on this, the deformation position of the flexible optical waveguide can be decoupled and calculated, thus realizing the dual detection of force and position.

[0038] In this embodiment, the specific steps of a tactile perception method for a distributed tactile sensor based on a flexible optical waveguide are as follows: (1) Calculate the optical loss of the first optical waveguide core 2 based on the input light intensity at the input end of the first optical waveguide core 2 and the light intensity detected by the photoelectric receiver of the first optical waveguide core 2; similarly, calculate the optical loss of the second optical waveguide core 5 based on the input light intensity at the input end of the second optical waveguide core 5 and the light intensity detected by the photoelectric receiver of the second optical waveguide core 5. (2) Obtain the magnitude of the force on the first optical waveguide core 2 according to the fitting relationship between the optical loss of the first optical waveguide core 2 and the force. (3) According to a series of fitting relationships between the optical losses at different positions of the second optical waveguide core 5 and the force, substitute the magnitude of the force on the first optical waveguide core 2 into the series of fitting relationships. When the optical loss is the same as the actual measurement result, it can be determined that deformation occurs at the position corresponding to this relationship, and the force application position data is obtained.

[0039] As described above, only a relatively simple embodiment of this patent is provided, but the protection scope of this patent is not limited thereto. Any person skilled in the art within the scope disclosed by this patent, according to the technical solution and inventive concept of this patent, makes equivalent substitutions or changes, and all belong to the protection scope of this patent.

Claims

1. A distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure, characterized in that, The tactile sensor mainly includes: a first optical waveguide (1), a second optical waveguide (4), and an outer cladding (8); Wherein, the first optical waveguide (1) includes a first optical waveguide core (2) and a first optical waveguide cladding (3); the second optical waveguide (4) includes a second optical waveguide core (5), a second optical waveguide lower cladding (6), and a second optical waveguide upper cladding (7); the first optical waveguide core (2) is in the middle of the first optical waveguide cladding (3); the second optical waveguide core (5) is in the middle of the second optical waveguide lower cladding (6) and the second optical waveguide upper cladding (7); the first optical waveguide core (2) and the second optical waveguide core (5) are arranged in parallel, and the first optical waveguide (1) and the second optical waveguide (4) are separated by the outer cladding (8); The refractive index of the first optical waveguide core (2) is greater than the refractive index of the first optical waveguide cladding (3); the refractive index of the second optical waveguide core (5) is greater than the refractive index of the second optical waveguide lower cladding (6) and the second optical waveguide upper cladding (7); so that frustrated total internal reflection occurs at the interfaces of the first optical waveguide (1), the second optical waveguide core (5), and the claddings; The second optical waveguide upper cladding (7) contains a plurality of microstructures, the microstructures are uniformly distributed along the input end to the output end direction, and the microstructures form a plurality of gradients along the input end to the output end direction according to the structural size or structural density of the microstructures, and the microstructures are arranged in parallel and in contact with the second optical waveguide core (5); The input end of the first optical waveguide core (2) is connected to a light source through an externally connected standard optical fiber, and the output end of the first waveguide core (2) is connected to a photodetector through an externally connected standard optical fiber; the input end of the second optical waveguide core (5) is connected to a light source through an externally connected standard optical fiber, and the output end of the second optical waveguide core (5) is connected to a photodetector through an externally connected standard optical fiber.

2. The distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure according to claim 1, wherein The cross-sections of the first optical waveguide (1) and the second optical waveguide (4) are rectangular as a whole, with a width between 1 and 5 mm and a height between 0.5 and 5 mm; the heights of the first optical waveguide (1) and the second optical waveguide (4) are equal to uniformly sense the external force; the cross-sections of the first optical waveguide core (2) and the second optical waveguide core (5) are rectangular, with a width between 0.05 and 3 mm and a height between 0.02 and 3 mm; the cross-sections of the first optical waveguide cladding (3), the second optical waveguide lower cladding (6), and the second optical waveguide upper cladding (7) are rectangular as a whole, with a length between 30 and 100 mm; the cross-section of the outer cladding (8) is rectangular as a whole, with a rectangular width between 2 and 10 mm and a height between 1 and 10 mm.

3. The distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure according to claim 1, wherein The microstructures are convex structures with micron-sized dimensions.

4. The distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure according to claim 3, wherein The convex structures are micro-pyramids, micro-creases, micro-column arrays, and microstructures replicated from plants.

5. The distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure according to claim 1, characterized in that, The second optical waveguide upper cladding (7) contains four microstructures with different structural sizes, and the microstructures are uniformly arranged along the input end to the output end direction in ascending order of structural size.

6. A preparation method of a distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure as described in claim 1, characterized in that, The steps of this method are as follows: 1) Prepare the first optical waveguide (1); The materials of the first optical waveguide core (2) and the first optical waveguide cladding (3) are respectively demolded by casting to obtain the preforms of the first optical waveguide core (2) and the first optical waveguide cladding (3); the first optical waveguide core (2) is placed into the groove of the preform of the first optical waveguide cladding (3), and the material of the first optical waveguide cladding (3) is injected again so that the first optical waveguide core (2) is encapsulated in the first optical waveguide cladding (3); the optical refractive index n of the material of the first optical waveguide core (2) and the material of the first optical waveguide cladding (3) 芯 and the optical refractive index n of the cladding material 包 meet the condition of frustrated total internal reflection; 2) Prepare the second optical waveguide core (5) and the second optical waveguide lower cladding (6); Place the material of the second optical waveguide core (5) into a mold. After the material is hot-pressed and formed, demold it to obtain a preform (14) of the second optical waveguide core. Process a groove on the upper surface of the material of the second optical waveguide lower cladding (6) that is in interference fit with the preform (14) of the second optical waveguide core, and place the preform (14) of the second optical waveguide core in the groove to obtain a preform (15) of the second optical waveguide. Prepare the second optical waveguide core and the second optical waveguide lower cladding (6) of the second optical waveguide (4) from the preform (15) of the second optical waveguide by the method of melting and drawing. The optical refractive index n 芯’ of the second optical waveguide core material and the optical refractive index n 包’ of the cladding material satisfy the condition of frustrated total internal reflection; 3) Prepare the microstructures and the second optical waveguide upper cladding (7); The microstructured materials are respectively cast on the surfaces of sandpapers with different mesh numbers. After the materials are cured, the cured films are detached from the sandpaper surfaces to obtain microstructures with different structural sizes. The material of the upper cladding (7) of the second optical waveguide is injected into the mold D, and then the above-mentioned materials are uniformly placed into the mold in the order of structural size from the input end to the output end. After the materials are cured, the mold is removed to obtain the upper cladding (7) of the second optical waveguide; the optical refractive index n 芯’ of the material of the inner core of the second optical waveguide and the optical refractive index n 包” of the material of the upper cladding (7) of the second optical waveguide satisfy the condition of frustrated total internal reflection; 4) Prepare the second optical waveguide (4); Cover the second optical waveguide upper cladding (7) on the second optical waveguide core (5), such that the microstructures included in the second optical waveguide upper cladding (7) are arranged in parallel and in contact with the second optical waveguide core (5); encapsulate all its sides with the material of the second optical waveguide upper cladding (7) or glue to obtain the second optical waveguide (4); 5) Package the distributed tactile sensor based on the flexible optical waveguide; Place the first optical waveguide (1) and the second optical waveguide (4) into the grooves of the mold, respectively connect the input end standard optical fiber and the output end standard optical fiber to the first optical waveguide (1) and the second optical waveguide (4) at both ends of the groove, such that the first optical waveguide core (2) and the second optical waveguide core are communicated with the standard optical fiber; package the optical waveguide sensor with the material of the outer cladding (8) to form the finished optical waveguide sensor.

7. The preparation method of the distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure according to claim 6, characterized in that, The material of the first optical waveguide core (2) is PDMS with a first ratio. The PDMS is a two-component silica gel, and the first ratio means that the ratio between PDMS and the curing agent is 5:1 by mass; the material of the first optical waveguide cladding (3) is PDMS with a second ratio, and the second ratio means that the ratio between PDMS and the curing agent is 10:1 by mass.

8. The preparation method of the distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure according to claim 7, characterized in that, The material of the second optical waveguide core is fluorinated acrylic pellet; the material of the second optical waveguide lower cladding (6) is PVDF.

9. The preparation method of the distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure according to claim 8, characterized in that, The material of the second optical waveguide upper cladding (7), the material of the microstructures, and the material of the outer cladding (8) are PDMS with a second ratio, and the second ratio means that the ratio between PDMS and the curing agent is 10:1 by mass.

10. A detection method for a distributed tactile sensor based on a flexible optical waveguide and a gradient microstructure as described in claim 1, characterized in that, The specific steps of this method are as follows: 1) Calculate the optical loss of the first optical waveguide core (2) based on the input optical intensity at the input end of the first optical waveguide core (2) and the optical intensity detected by the optical receiver of the first optical waveguide core (2); Similarly, calculate the optical loss of the second optical waveguide core based on the input optical intensity at the input end of the second optical waveguide core and the optical intensity detected by the optical receiver of the second optical waveguide core; 2) Obtain the magnitude of the force on the first optical waveguide core (2) according to the fitting relationship between the optical loss of the first optical waveguide core (2) and the force; 3) According to the series of fitting relationships between the optical loss at different positions of the second optical waveguide core and the force, substitute the magnitude of the force on the first optical waveguide core (2) into the series of fitting relationships. When the optical loss is the same as the actual measurement result, it can be determined that deformation occurs at the position corresponding to this relationship, and the force position data is obtained.

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