Optical fiber force tactile sensor and measuring system

Abstract

The invention relates to the technical field of optical detection and optical fiber sensing, in particular to an optical fiber force tactile sensor and a measuring system. The optical fiber force touch sensor adopts a finger-shaped structural design and comprises a silica gel fingertip, a bent optical fiber Sagnac interference structure and a resin finger body, the measuring system comprises a broadband light source, an optical fiber coupler, an optical fiber force touch sensor and a spectrograph. The sensor can be integrated on a mechanical finger, the silica gel fingertip generates corresponding elastic deformation under the action of external force, so that the bent optical fiber Sagnac interference structure deforms at the same time, the stress sensitive characteristic of the optical fiber Sagnac interference structure is utilized, blue shift occurs in a transmission spectrum, and fingertip pressure sensing is achieved. The silica gel fingertips have the heat insulation characteristic, and the temperature cross sensitivity of the sensor can be effectively reduced. The sensor is free of electromagnetic interference, simple in structure, low in cost and high in sensitivity, can overcome the defects of sensors based on the electrical principle, and can adapt to various task scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical detection and fiber sensing technology, and particularly relates to a fiber force tactile sensor and a measuring system. BACKGROUND

[0002] Force tactile is a force sense that detects the size of force, which can help humans perceive the surrounding environment and identify objects. Force tactile sensors can assist robots in performing tasks such as picking and grabbing, human-computer interaction, which makes force tactile sensors widely concerned by researchers. Various force tactile sensors with different principles have been manufactured and applied to different fields.

[0003] In 2017, Levent Beker et al. designed a stretchable film type double-layer sensor. When the sensor is subjected to pressure, the filler will deform, causing the distance between the two layers of film to change, thereby changing the capacitance value. According to the change of the capacitance value, the pressure, deformation and hardness of the object can be perceived. In 2016, Guo Yongxing et al. designed a three-dimensional force fingertip sensor based on the FBG sensing principle. Two groups of FBG are distributed inside the sensor. One group of FBG is in close contact with the internal structure to sense the strain of the axial force, and the other group of FBG is in a free state without stress and strain, serving as a reference FBG. Four groups of FBG are distributed on the four beams outside the sensor to measure the lateral force around the sensor.

[0004] Traditional force tactile sensors are mainly based on resistance, capacitance or piezoelectric principles, which are susceptible to electromagnetic interference and difficult to work stably in humid or high-temperature environments. Although fiber optic sensors have advantages such as electromagnetic interference resistance and corrosion resistance, they also have problems such as temperature cross-sensitivity and complex structure. Moreover, existing sensor designs mostly use rigid packaging, which makes it difficult to integrate with mechanical fingers. Although fiber Sagnac interference sensors have high sensitivity, their application in finger sleeve type force tactile sensors is still immature, especially in maintaining miniaturization while achieving high-precision force perception. SUMMARY

[0005] Therefore, the present application provides a fiber force tactile sensor and a measuring system, which realizes accurate force tactile perception to overcome the problems of electromagnetic interference, temperature cross-sensitivity, complex structure and difficulty in integration in the prior art.

[0006] To achieve the above purpose, in one aspect, the present application provides a fiber force tactile sensor, comprising: a silica gel fingertip for contacting external objects and producing elastic deformation; an embedded curved fiber Sagnac interference structure for realizing pressure sensing by deformation-induced transmission spectrum shift; and a resin finger body connected with the silica gel fingertip, the resin finger body being a hollow structure and being suitable for integration on a mechanical finger.

[0007] Further, the silica gel fingertip is made of silica gel material, has a height of 1.8 cm, and has heat insulation characteristics, which can effectively reduce the temperature cross-sensitivity of the sensor.

[0008] Further, the resin finger body is made of photosensitive resin material by light curing 3D printing technology, has a diameter of 1.8 cm, and a length of 3 cm.

[0009] Further, the curved fiber Sagnac interference structure has stress sensitivity characteristics, and the blue shift amount of the transmission spectrum has a linear relationship with the pressure size.

[0010] Further, the curved fiber Sagnac interference structure is sequentially fused by a first single-mode optical fiber, a panda-type polarization maintaining optical fiber, and a second single-mode optical fiber.

[0011] Further, the resin finger body has symmetrically distributed first and second optical fiber grooves with a depth of 0.5 mm and a width of 1 mm, which are used to fix the first and second single-mode optical fibers.

[0012] Further, the first and second single-mode optical fibers are respectively C1 and C2 ports of the fiber force tactile sensor.

[0013] Further, the length of the panda-type polarization maintaining optical fiber is 5.5 cm.

[0014] On the other hand, the application also provides a measurement system, which comprises a broadband light source, a fiber coupler, a fiber force tactile sensor, and a spectrometer, and is used to realize light signal transmission, interference, and demodulation.

[0015] The relationship between the elements of the measurement system is as follows:

[0016] The light output port A1 port of the broadband light source is connected to the B1 port of the fiber coupler.

[0017] The B2 and B3 ports of the fiber coupler are respectively connected to the C1 and C2 ports of the fiber force tactile sensor.

[0018] The B4 port of the fiber coupler is connected to the D1 input port of the spectrometer.

[0019] Compared with the prior art, the fiber force tactile sensor of the application adopts a finger-shaped structure design, which comprises a silica gel fingertip, a curved fiber Sagnac interference structure, and a resin finger body.

[0020] Further, the silica gel fingertip is made of silica gel material, has heat insulation characteristics, and can effectively reduce the temperature cross-sensitivity of the sensor.

[0021] Further, the resin finger body is made of photosensitive resin material by light curing 3D printing technology, and the hollow structure can be designed flexibly and integrated with the mechanical finger.

[0022] Further, the curved fiber Sagnac interference structure has stress-sensitive characteristics, and the blue shift amount of the transmission spectrum is linearly related to the pressure size, so that the change of contact force can be detected, and the finger force tactile perception is simulated.

[0023] Further, the curved fiber Sagnac interference structure is formed by sequentially fusing a first single-mode optical fiber, a panda polarization maintaining optical fiber and a second single-mode optical fiber, and has simple structure and electromagnetic interference resistance.

[0024] Further, the length of the panda polarization maintaining optical fiber is 5.5 cm.

[0025] Further, the application further provides a measurement system, which comprises a broadband light source, a fiber coupler, a fiber force tactile sensor and a spectrometer, and is used for realizing light signal transmission, interference and demodulation. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A structural schematic diagram of a fiber force tactile sensor provided by the embodiment of the application.

[0027] Figure 2 A structural block diagram of a fiber force tactile sensor measurement system provided by the embodiment of the application.

[0028] Figure 3 A force tactile transmission spectrum diagram based on the fiber force tactile sensor provided by the embodiment of the application.

[0029] Figure 4 A force tactile fitting diagram based on the fiber force tactile sensor provided by the embodiment of the application.

[0030] Figure 5 A temperature cross-sensitivity transmission spectrum based on the fiber force tactile sensor provided by the embodiment of the application.

[0031] Figure 6 A temperature cross-sensitivity fitting diagram based on the fiber force tactile sensor provided by the embodiment of the application. DETAILED DESCRIPTION

[0032] In order to make the purpose and advantages of the application clearer and more apparent, the application will be further described below in combination with embodiments; it should be understood that the specific embodiments described herein are only used to explain the application, and do not limit the application.

[0033] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art will understand that the embodiments are only used to explain the technical principles of the present application and are not intended to limit the protection scope of the present application.

[0034] It should be noted that in the description of the present application, the terms indicating the direction or positional relationship of "upper", "lower", "left", "right", "inner", "outer" and the like are based on the direction or positional relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0035] In addition, it should also be noted that in the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the communication inside two elements. Those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0036] Please refer to Figure 1 The optical fiber force tactile sensor prepared by the present application is shown in the figure, and the specific preparation process is as follows:

[0037] Step (1) resin finger body is made by using light curing 3D printer. The resin finger body has a diameter of 1.8 cm and a length of 3 cm; the hollow structure inside has a cross-sectional side length of 1.4 cm and 0.6 cm, respectively; the first optical fiber groove and the second optical fiber groove are symmetrically distributed, with a depth of 0.5 mm and a width of 1 mm.

[0038] Step (2) make optical fiber Sagnac interference structure. Use optical fiber fusion splicer to fuse the first single-mode optical fiber, 5.5 cm panda polarization maintaining optical fiber and second single-mode optical fiber in sequence, and the fusion loss is less than 0.03 dB at each place.

[0039] Step (3) bend the optical fiber Sagnac interference structure into the resin finger structure, with the panda polarization maintaining optical fiber in a bent state, the first single-mode optical fiber horizontally placed into the first optical fiber groove, and the second single-mode optical fiber horizontally placed into the second optical fiber groove. The first optical fiber groove and the second optical fiber groove are smeared with glue to fix the optical fiber.

[0040] Step (4) pour the prepared silicone liquid into the silicone finger mold, place the resin finger body and the fixed bent optical fiber Sagnac interference structure into the silicone mold, and after 24 hours of standing, remove the silicone mold, and the optical fiber force tactile sensor is prepared.

[0041] Please refer toFigure 2 As shown in the structural block diagram of the optical fiber force tactile sensor measurement system provided by the application, the system comprises a broadband light source, a fiber coupler, an optical fiber force tactile sensor and a spectrometer, and is used for realizing optical signal transmission, interference and demodulation; wherein: the relationship between the elements of the measurement system is as follows: the light output port A1 of the broadband light source is connected to the B1 port of the fiber coupler, the B2 port and the B3 port of the fiber coupler are connected to the C1 port and the C2 port of the optical fiber force tactile sensor respectively, and the B4 port of the fiber coupler is connected to the input port D1 of the spectrometer.

[0042] The broadband light source is used for generating an optical signal at the light output port A1 and sending the optical signal to the B1 port of the fiber coupler.

[0043] The fiber coupler is used for dividing the light received by the B1 port into two beams of light with the same intensity and opposite directions, outputting the two beams of light at the B2 port and the B3 port of the fiber coupler, coupling the two beams of light into the C1 port and the C2 port of the optical fiber force tactile sensor, and coupling the two beams of transmitted light from the optical fiber force tactile sensor into the input port D1 of the spectrometer.

[0044] The optical fiber force tactile sensor is used for receiving external pressure.

[0045] The spectrometer is used for demodulating the received transmitted light signal.

[0046] It should be noted that the broadband light source, the fiber coupler and the spectrometer are determined according to actual application, and the embodiment is not specifically limited. For example, the working wavelength of the broadband light source is 1528nm-1568nm, the fiber coupler is a 2×23dB coupler, and the resolution of the spectrometer is 14pm.

[0047] Specifically, the silica gel fingertip contacts an external object and produces elastic deformation, the built-in bent optical fiber Sagnac interference structure simultaneously produces deformation, the phase difference of the two beams of transmitted light passing through the optical fiber force tactile sensor changes, which causes the transmitted light spectrum to shift to realize pressure sensing.

[0048] The phase difference φ satisfies the following formula:

[0049]

[0050] The period of the transmitted light spectrum of the optical fiber force tactile sensor can be represented by a free spectral range:

[0051]

[0052] Wherein, λ is the wavelength of the transmitted light spectrum, B is the birefringence of the polarization maintaining optical fiber, and L is the length of the panda-type polarization maintaining optical fiber.

[0053] Please refer toFigure 3 As shown in the figure, it is a force tactile transmission spectrum diagram of the fiber force tactile sensor according to the embodiment of the present application.

[0054] The change range of the external stress is 0-2.0N, and the transmission spectrum of the fiber force tactile sensor is blue-shifted with the increase of the external stress.

[0055] Please refer to Figure 4 As shown in the figure, it is a force tactile fitting diagram of the fiber force tactile sensor according to the embodiment of the present application.

[0056] The fitting curve obtains that the force tactile sensitivity of the fiber force tactile sensor is 4.002nm / N, and the determination coefficient R 2 is 0.997.

[0057] Please refer to Figure 5 As shown in the figure, it is a temperature cross-sensitivity transmission spectrum diagram of the fiber force tactile sensor according to the embodiment of the present application.

[0058] The change range of the external temperature is 50-55℃, and the transmission spectrum of the fiber force tactile sensor is blue-shifted with the increase of the external temperature.

[0059] Please refer to Figure 6 As shown in the figure, it is a temperature cross-sensitivity fitting diagram of the fiber force tactile sensor according to the embodiment of the present application.

[0060] The fitting curve obtains that the temperature cross-sensitivity sensitivity of the fiber force tactile sensor is 0.143nm / N, and the determination coefficient R 2 is 0.942.

[0061] So far, the technical scheme of the present application has been described in combination with the preferred embodiments shown in the drawings, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical scheme after the changes or replacements will fall within the protection scope of the present application.

Claims

1. A fiber optic force-tactile sensor, characterized in that, include: Silicone fingertips (1) are used to contact external objects and produce elastic deformation; The built-in bent fiber Sagnac interference structure (2) achieves pressure sensing by causing a shift in the transmission spectrum through deformation; the resin finger body (3) is connected to the silicone fingertip (1), and the resin finger body (3) has a hollow structure, which is suitable for integration into the mechanical finger.

2. The fiber optic force-tactile sensor according to claim 1, characterized in that, The silicone fingertip (1) is made of silicone material, has a height of 1.8cm, and has heat insulation properties, which can effectively reduce the temperature cross-sensitivity of the sensor.

3. The fiber optic force-tactile sensor according to claim 1, characterized in that, The resin finger body (3) is made of photosensitive resin material by photocuring 3D printing technology, with a diameter of 1.8cm and a length of 3cm.

4. The fiber optic force-tactile sensor according to claim 1, characterized in that, The bent fiber Sagnac interference structure (2) has stress-sensitive characteristics, and the blue shift of the transmission spectrum is linearly related to the magnitude of the pressure.

5. The fiber optic force-tactile sensor according to claim 1, characterized in that, The bent fiber Sagnac interference structure is formed by sequentially splicing a first single-mode fiber (6), a panda-type polarization-maintaining fiber, and a second single-mode fiber (7).

6. The fiber optic force-tactile sensor according to claim 1, characterized in that, The resin finger has a first fiber groove (4) and a second fiber groove (5) symmetrically distributed, with a depth of 0.5 mm and a width of 1 mm, for fixing the first single-mode fiber (6) and the second single-mode fiber (7).

7. The fiber optic force-tactile sensor according to claim 5, characterized in that, The first single-mode fiber (6) and the second single-mode fiber (7) are the C1 port and C2 port of the fiber optic force tactile sensor, respectively.

8. The fiber optic force-tactile sensor according to claim 5, characterized in that, The length of the panda-shaped polarization-maintaining fiber is 5.5 cm.

9. A measurement system for the fiber optic force-tactile sensor according to any one of claims 1-8, characterized in that, The measurement system includes a broadband light source (7), an optical fiber coupler (8), an optical fiber force sensor, and a spectrometer (9), which are used to realize optical signal transmission, interference, and demodulation. The relationships between the components of the measurement system are as follows: the light output port A1 of the broadband light source (7) is connected to the B1 port of the fiber optic coupler (8), the B2 and B3 ports of the fiber optic coupler (8) are connected to the C1 and C2 ports of the fiber optic force tactile sensor, respectively, and the B4 port of the fiber optic coupler (8) is connected to the D1 input port of the spectrometer (9).

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