Intelligent bionic sensing system based on optical fiber tactile perception

Abstract

The present invention discloses an intelligent bionic sensing system based on fiber optic tactile perception, which is characterized by including a fiber optic bionic sensor, an optical path subsystem, and a tactile signal intelligent processing subsystem; the fiber optic bionic sensor is used to obtain the tactile signal of the object under test and convert the tactile signal; the optical path subsystem is used to obtain a tactile light signal based on the converted tactile signal, and obtain the surface temperature of the object under test based on the tactile light signal; the tactile signal intelligent processing subsystem is used to identify the hardness and surface roughness of the object under test based on the tactile light signal. The present invention can realize the perception of temperature, pressure and vibration and quantitative detection based on vibration signals, and realize the digitization and intelligent feature recognition of tactile information through the intelligent signal processing system, truly realizing intelligent tactile perception. The system will provide important technical and hardware support for application fields such as medical diagnosis, human-computer interaction, intelligent robots, and human body function enhancement.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber bionic sensing, and in particular relates to an intelligent bionic sensing system based on optical fiber tactile perception. Background Art

[0002] The human body primarily relies on the five sensory systems (also known as the "five senses")—vision, hearing, smell, taste, and touch—to acquire and perceive information about the external environment. These senses, which are converted into electrical impulses by relevant organs (neurons and sensory cells), are then transmitted to the brain for processing and analysis, ultimately enabling perception and cognition of the external environment. The biological mechanisms underlying these organs have long been a vexing mystery for scientists. However, human perception is influenced by environmental, physiological, and psychological factors, and is highly subjective and subject to individual variation. This reduces the reliability of information and complicates the quantitative assessment and transmission of environmental information. Instrument-based detection technologies, on the other hand, can generate stable environmental signals and provide quantitative feedback. Therefore, ensuring interoperability between instrument feedback and human perception is crucial for advancing human-computer interaction technology and understanding the biological mechanisms of human organs. Artificial bionic detection technologies and systems, particularly intelligent bionic systems, provide an effective bridge between human perception and quantitative machine detection. Furthermore, understanding the biological mechanisms of human organs can significantly enhance the intelligence and performance of instruments. For example, after humans mastered the physiological mechanisms of visual perception, visual intelligent perception technology has rapidly developed, giving rise to intelligent image processing systems represented by graphics processing units (GPUs). Their image processing and recognition capabilities far exceed those of the human eye, enabling them to handle image perception in a wide range of complex scenes. This has laid the hardware foundation and guarantee for the development of fields such as autonomous vehicles and VR imaging. Therefore, the development of intelligent bionic systems and technologies is of great significance.

[0003] However, truly simulating the sophisticated human sensory nervous system is a significant challenge. This requires not only high sensor sensitivity, high accuracy, and strong anti-interference capabilities, but also robust signal transmission systems and good threshold controllability. Furthermore, to fully and realistically simulate the human sensory system, it is necessary to construct a multifunctional neural feedback unit and achieve multimodal sensor fusion (such as vision-touch, image-speech fusion, etc.). For example, the use of a "vision-touch" dual-modal bionic system can enhance signal recognition capabilities in dark environments, thereby improving the work efficiency of the robot arm.

[0004] Touch is often considered the "mother of all perceptions." It primarily occurs when receptors (such as receptor cells and neurons) within the skin generate electrical signals in response to external stimuli. These signals are then transmitted to the brain to create a "tactile image." This "tactile image" enables humans to perceive information such as hot or cold, dry or wet, smooth or rough, soft or hard. Touch primarily involves the human body's perception of physical parameters such as ambient temperature and mechanical forces (pressure, strain, and vibration). The tactile perception process involves more than simply converting a physical property into an electrical neural signal; it also involves processing and analyzing the signal and deriving its correlation with the corresponding visual image—an intelligent computational process. Therefore, to achieve intelligent bionic perception, the system must possess capabilities such as quantitative extraction, analysis, and intelligent representation of tactile signals. Simulating and constructing bionic tactile perception systems is a fundamental scientific problem and key technology required for research in fields such as human-computer interaction, medical research, biology, and human enhancement. Furthermore, tactile perception systems can be used in medical diagnosis, human rehabilitation, and human-machine enhancement. They can also enable robots to possess human-like perception capabilities, ultimately enabling truly seamless information exchange between humans, machines, and the environment. Therefore, the development of bionic tactile intelligent perception systems is of great significance and urgent need.

[0005] Human touch primarily involves the perception of key physical parameters such as ambient temperature, pressure, and vibration. Temperature perception is the primary step in regulating the body's response to external temperature changes; pressure perception is used by the body to perceive the authenticity and hardness of external materials; and the body's ability to discern the roughness and smoothness of surface textures relies primarily on the perception of friction and vibration. Therefore, the ability to perceive these three basic physical parameters, temperature, pressure, and vibration, is a fundamental sensing capability that a tactile bionic sensing system must possess. Furthermore, current artificial perception systems can only perform simple analytical calculations, such as threshold assessment and peak detection, making it difficult to achieve true correlated perception of environmental events. Therefore, a bionic tactile perception system must possess "thinking power," meaning its signal processing subsystem must possess brain-like deep learning capabilities (i.e., a neural network must be constructed) to ultimately achieve the digitization of human senses.

[0006] Currently, there is no effective technical means to fully simulate and realize the tactile perception function of human skin. As for traditional electrical temperature, pressure, and vibration sensors, their application range is limited by defects such as large size, electromagnetic interference, low sensitivity, and parasitic effects. In contrast, fiber optic sensors developed in recent years have attracted widespread attention due to their compact structure, resistance to electromagnetic interference, high sensitivity, short response time, and easy networking. It is worth noting that the existing fiber optic sensors that can be used in the field of tactile bionic sensing are relatively simple in function and can only sense one or two parameters among temperature, pressure, and vibration. If a tactile bionic sensing system is constructed based on existing fiber optic sensors, the complexity and cost of the system will increase accordingly. Summary of the Invention

[0007] To address these issues, the present invention proposes an intelligent biomimetic sensing system based on fiber-optic tactile perception, aiming to address the existing problem of being unable to quantitatively analyze tactile perception. The sensor is compact and simple in structure, and can digitally inform, visualize, and intelligently analyze tactile perception.

[0008] To achieve the above objectives, the present invention provides an intelligent bionic sensing system based on optical fiber tactile perception, comprising an optical fiber bionic sensor, an optical path subsystem, and an intelligent tactile signal processing subsystem;

[0009] The optical fiber bionic sensor is used to obtain tactile signals of the object being measured and convert the tactile signals;

[0010] The optical path subsystem is used to obtain a tactile light signal according to the converted tactile signal, obtain the surface temperature of the measured object according to the tactile light signal, and transmit the tactile light signal to the tactile signal intelligent processing subsystem;

[0011] The tactile signal intelligent processing subsystem is used to identify the hardness and surface roughness of the object under test according to the tactile light signal.

[0012] Optionally, the optical fiber bionic sensor includes a fingerprint-like contact layer and a flexible sensing layer;

[0013] The fingerprint-like contact layer is used to obtain the tactile signal and transmit the tactile signal to the flexible sensing layer;

[0014] The flexible sensing layer is used to convert the temperature signal, pressure signal and vibration signal.

[0015] Optionally, the flexible sensing layer includes a PDMS packaging layer and a micro-nano optical fiber coupler;

[0016] The PDMS packaging layer is used to transmit the tactile signal to the micro-nano optical fiber coupler;

[0017] The micro-nano optical fiber coupler includes a micro-nano optical fiber coupler port I, a micro-nano optical fiber coupler port II, a micro-nano optical fiber coupler port III, and a micro-nano optical fiber coupler port IV;

[0018] The micro-nano optical fiber coupler is used to convert the tactile signal.

[0019] Optionally, the tactile signal includes a temperature signal, a pressure signal and a vibration signal;

[0020] The micro-nano optical fiber coupler converts the temperature signal into a characteristic wavelength drift of light in the micro-nano optical fiber coupler;

[0021] The micro-nano optical fiber coupler converts the pressure signal and the vibration signal into the bending strain of the micro-nano optical fiber coupler.

[0022] Optionally, the optical path subsystem includes an ASE broadband light source, a 50 / 50 fiber coupler, a spectrum analyzer, a narrowband bandpass filter, a first photodetector, a second photodetector, and a digital acquisition card;

[0023] The ASE broadband light source is connected to the optical fiber bionic sensor via the micro-nano optical fiber coupler port I, and is used to output a broadband light beam to the optical fiber bionic sensor;

[0024] The 50 / 50 optical fiber coupler is connected to the optical fiber bionic sensor via the micro-nano optical fiber coupler port III;

[0025] The 50 / 50 fiber coupler includes a 50 / 50 fiber coupler output port I and a 50 / 50 fiber coupler output port II;

[0026] The spectrum analyzer is connected to the 50 / 50 optical fiber coupler via the 50 / 50 optical fiber coupler output port I, and the spectrum analyzer is used to detect the surface temperature of the object to be measured based on the characteristic wavelength drift of the light;

[0027] The narrowband bandpass filter is connected to the 50 / 50 optical fiber coupler through the 50 / 50 optical fiber coupler output port II, and the narrowband bandpass filter is also connected to the optical fiber bionic sensor through the micro-nano optical fiber coupler port IV;

[0028] The narrowband bandpass filter and the digital acquisition card are connected respectively through the first photodetector and the second photodetector. The digital acquisition card is used to collect the second tactile light signal output by the first photodetector and the first tactile light signal output by the second photodetector, and transmit them to the tactile signal intelligent processing subsystem.

[0029] Optionally, the optical signal path in the optical path subsystem is:

[0030] The broadband light source outputs a broadband light beam, which is input into the fiber bionic sensor through the micro-nano fiber coupler port I. In the fiber bionic sensor, the broadband light beam is split into a first light beam and a second light beam. The first light beam is output from the micro-nano fiber coupler port III to the 50 / 50 fiber coupler and is further split into a third light beam and a fourth light beam. The third light beam is output through the 50 / 50 fiber coupler output port I and enters the optical spectrum analyzer OSA for detecting the surface temperature of the object under test by monitoring the characteristic wavelength drift. The fourth light beam is output through the 50 / 50 fiber coupler output port II, enters the narrowband bandpass filter, and then enters the second photodetector to obtain the first tactile light signal. The second light beam is output through the micro-nano fiber coupler port IV, enters the narrowband bandpass filter, and then enters the first photodetector to obtain the second tactile light signal. Both the first tactile light signal and the second tactile light signal are collected by the digital acquisition card.

[0031] Optionally, the method for preparing the fingerprint-like contact layer is: based on PTFE, 3D printing a "concentric" elliptical ring reverse structure mold, and preparing the fingerprint-like contact layer based on the first ratio of PDMS solution and the reverse structure mold.

[0032] Optionally, the PDMS encapsulation layer is prepared by uniformly coating a PDMS solution having a second ratio on a Teflon substrate, spin-coating the PDMS solution using a three-stage spin coating method, and heating and curing the spin-coated PDMS solution to prepare the PDMS encapsulation layer;

[0033] The method for preparing the micro-nano optical fiber coupler comprises: stripping the plastic coating layer of the tapered portion of two conventional commercial single-mode optical fibers, twisting the exposed portions together, fixing and heating them, and then tapering them to prepare the micro-nano optical fiber coupler;

[0034] The preparation method of the flexible sensing layer is: embedding the micro-nano optical fiber coupler into the PDMS packaging layer to prepare the flexible sensing layer.

[0035] Optionally, the preparation method of the optical fiber bionic sensor is: based on the PDMS solution of the second ratio, the fingerprint-like contact layer and the flexible sensing layer are bonded together, and heated and cured to prepare the optical fiber bionic sensor.

[0036] Compared with the prior art, the present invention has the following advantages and technical effects:

[0037] The present invention utilizes the large-scale evanescent field of the micro-nano fiber coupler and the large negative thermo-optic coefficient of PDMS to detect temperature through the wavelength drift caused by temperature-induced refractive index changes, with a sensitivity of up to 2.5nm / ℃.

[0038] The present invention utilizes a fingerprint-like raised elliptical ring-shaped contact layer structure, which can detect not only relative friction movement in one-dimensional single direction, but also relative friction movement in two-dimensional directions.

[0039] The present invention utilizes the flexibility of the PDMS encapsulation layer and the micro-nano fiber coupler to sensitively detect the degree of longitudinal strain and lateral relative friction movement occurring on the surface of the contact layer, and characterizes the hardness and roughness and smoothness of the surface texture of the corresponding measured object in the form of the characteristic amplitude and frequency of the tactile vibration signal.

[0040] The present invention uses wavelet transformation to extract features from the obtained tactile signals, and then uses a machine learning algorithm to classify the feature signals of different frequencies corresponding to the surface texture features of different objects and establish a database. The obtained tactile signals are then cross-correlated with the feature signals in the database after feature extraction to determine whether they match, thereby achieving the purpose of feature recognition.

[0041] The present invention can first use a fingerprint-like contact layer to contact the surface of the object to be measured to detect its surface temperature, and then press or rub the object to be measured to detect its hardness and surface roughness. After feature extraction, its tactile vibration signal is feature matched with the feature signals in the established database, thereby realizing the tactile bionic function of simultaneously detecting the surface temperature of the object and identifying the hardness and surface roughness of the object. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0043] Figure 1 This is a schematic structural diagram of an intelligent bionic sensing system based on optical fiber tactile perception according to the first embodiment of the present invention;

[0044] Figure 2 This is a schematic structural diagram of an optical fiber bionic sensor according to the first embodiment of the present invention;

[0045] Figure 3 This is a front view of the optical fiber biomimetic sensor according to the first embodiment of the present invention;

[0046] Figure 4 1 is a top view of the optical fiber biomimetic sensor according to the first embodiment of the present invention;

[0047] Figure 5Schematic diagram of the processing flow of the tactile signal intelligent processing subsystem according to the first embodiment of the present invention;

[0048] Among them, 1. Conventional commercial single-mode optical fiber; 2. Tapered transition zone of micro-nano optical fiber; 3. Uniform waist region of micro-nano optical fiber; 4. Fingerprint-like contact layer; 5. PDMS encapsulation layer; 6. Micro-nano optical fiber coupler port I; 7. Micro-nano optical fiber coupler port II; 8. Micro-nano optical fiber coupler port III; 9. Micro-nano optical fiber coupler port IV; 10. ASE broadband light source; 11. Fiber optic bionic sensor; 12. 50 / 50 optical fiber coupler; 13. 50 / 50 optical fiber coupler output port I; 14. 50 / 50 optical fiber coupler output port II; 15. Spectrum analyzer; 16. Narrowband bandpass filter; 17. First photodetector; 18. Second photodetector; 19. Digital acquisition card; 20. Tactile signal intelligent processing subsystem. DETAILED DESCRIPTION

[0049] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0050] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0051] The present invention provides an intelligent bionic sensing system based on optical fiber tactile perception, comprising an optical fiber bionic sensor 11, an optical path subsystem, and a tactile signal intelligent processing subsystem 20; wherein the tactile signal intelligent processing subsystem 20 (Tactile signal intelligent processing subsystem) is referred to as TSPS.

[0052] The optical fiber bionic sensor 11 is used to obtain the tactile signal of the object being measured and convert the tactile signal;

[0053] The optical path subsystem is used to obtain a tactile light signal according to the converted tactile signal, obtain the surface temperature of the object under test according to the tactile light signal, and transmit the tactile light signal to the tactile signal intelligent processing subsystem;

[0054] The tactile signal intelligent processing subsystem 20 is used to extract and classify the features of the tactile light signal, establish a database, perform signal feature matching, and identify the hardness and surface roughness of the object being measured.

[0055] The optical fiber bionic sensor 11 includes a fingerprint-like contact layer 4 and a flexible sensing layer;

[0056] The fingerprint-like contact layer is a "concentric" elliptical ring-shaped protrusion, which is used to obtain tactile signals and transmit them to the flexible sensing layer;

[0057] The flexible sensing layer is used to convert temperature signals, pressure signals and vibration signals.

[0058] The flexible sensing layer includes a PDMS packaging layer 5 and a micro-nano optical fiber coupler;

[0059] The PDMS encapsulation layer 5 is used to transmit the tactile signal to the micro-nano optical fiber coupler;

[0060] The micro-nano optical fiber coupler includes a micro-nano optical fiber coupler port I6, a micro-nano optical fiber coupler port II7, a micro-nano optical fiber coupler port III8, and a micro-nano optical fiber coupler port IV9;

[0061] Micro-nano fiber optic couplers are used to convert tactile signals.

[0062] Tactile signals include temperature signals, pressure signals and vibration signals;

[0063] The micro-nano fiber coupler converts the temperature signal into the characteristic wavelength drift of the light in the micro-nano fiber coupler;

[0064] The micro-nano optical fiber coupler converts the pressure signal and the vibration signal into the bending strain of the micro-nano optical fiber coupler.

[0065] The optical subsystem includes an ASE broadband light source 10, a 50 / 50 fiber coupler 12, an optical spectrum analyzer 15, a narrowband bandpass filter 16, a first photodetector 17, a second photodetector 18, and a digital acquisition card 19; the ASE broadband light source 10 is referred to as ASE, the optical spectrum analyzer 15 is referred to as OSA, the narrowband bandpass filter 16 is referred to as BPF, and the digital acquisition card 19 is referred to as DAQ.

[0066] The ASE broadband light source 10 is connected to the optical fiber bionic sensor 11 through the micro-nano optical fiber coupler port I 6, and is used to output a broadband light beam to the optical fiber bionic sensor 11;

[0067] The 50 / 50 fiber coupler 12 is connected to the fiber bionic sensor 11 via the micro-nano fiber coupler port III 8;

[0068] The 50 / 50 fiber coupler 12 includes a 50 / 50 fiber coupler output port I 13 and a 50 / 50 fiber coupler output port II 14;

[0069] The spectrum analyzer 15 is connected to the 50 / 50 fiber coupler 12 via the 50 / 50 fiber coupler output port I 13 , and the spectrum analyzer 15 is used to detect the surface temperature of the object under test based on the characteristic wavelength drift of light;

[0070] The narrowband bandpass filter 16 is connected to the 50 / 50 fiber coupler 12 via the 50 / 50 fiber coupler output port II 14 , and the narrowband bandpass filter 16 is also connected to the fiber bionic sensor 11 via the micro-nano fiber coupler port IV 9 ;

[0071] The narrowband bandpass filter 16 and the digital acquisition card 19 are connected respectively through the first photodetector 17 and the second photodetector 18. The digital acquisition card 19 is used to collect the second tactile light signal output by the first photodetector 17 and the first tactile light signal output by the second photodetector 18, and transmit them to the tactile signal intelligent processing subsystem 20.

[0072] The optical signal path in the optical path subsystem is:

[0073] The ASE broadband light source 10 outputs a broadband light beam, which is input into the fiber bionic sensor 11 through the micro-nano fiber coupler port I6. In the fiber bionic sensor 11, the broadband light beam is split into a first light beam and a second light beam. The first light beam is output from the micro-nano fiber coupler port III8 to the 50 / 50 fiber coupler 12 and is further split into a third light beam and a fourth light beam. The third light beam is output through the 50 / 50 fiber coupler output port I13 and enters the optical spectrum analyzer 15, which is used to monitor the surface temperature of the object under test by monitoring the characteristic wavelength drift; the fourth light beam is output through the 50 / 50 fiber coupler output port II14 and enters the narrowband bandpass filter 16 and then enters the second photodetector 18 to obtain a first tactile light signal; the second light beam is output through the micro-nano fiber coupler port IV9 and enters the narrowband bandpass filter 17 and then enters the first photodetector 17 to obtain a second tactile light signal. Both the first tactile light signal and the second tactile light signal are collected by the digital acquisition card 19.

[0074] The fingerprint-like contact layer 4 is prepared by 3D printing a PTFE-based, concentric, elliptical reverse-structure mold. A first-ratio PDMS solution is used with the reverse-structure mold to prepare the fingerprint-like contact layer 4. The first-ratio PDMS solution comprises a base material and a curing agent in a weight ratio of 20:1.

[0075] The preparation method of the PDMS encapsulation layer 5 is as follows: the PDMS solution based on the second ratio is evenly coated on the Teflon substrate, the PDMS solution is spin-coated by a three-stage spin coating method, and the PDMS encapsulation layer 5 is prepared by heating and curing the spin-coated PDMS solution; the PDMS solution of the second ratio is a PDMS with a main agent and a curing agent weight ratio of 10:1.

[0076] The preparation method of the micro-nano fiber coupler is as follows: based on two conventional commercial single-mode optical fibers, the plastic coating layer of the tapered part is stripped, the exposed parts after stripping are twisted together, fixed and heated, and then tapered to prepare the micro-nano fiber coupler.

[0077] The method for preparing the flexible sensing layer is as follows: embedding the micro-nano optical fiber coupler into the PDMS packaging layer 5 to prepare the flexible sensing layer.

[0078] The preparation method of the optical fiber bionic sensor 11 is as follows: based on the PDMS solution with the second ratio, the fingerprint-like contact layer 4 and the flexible sensing layer are bonded together, and then heated and cured to prepare the optical fiber bionic sensor 11.

[0079] Example 1

[0080] like Figure 1 This embodiment provides an intelligent biomimetic sensing system based on fiber optic tactile perception, comprising a fiber optic biomimetic sensor 11, an optical path subsystem, and a tactile signal intelligent processing subsystem 20. The fiber optic biomimetic sensor 11 includes a fingerprint-like contact layer 4 and a flexible sensing layer, a PDMS encapsulation layer 5, and a micro-nano fiber optic coupler. The tactile signal intelligent processing subsystem 20 includes wavelet transform, machine learning-based feature classification, and signal feature matching.

[0081] The fingerprint-like contact layer 4 is made of polymer material PDMS, and has a "concentric" elliptical ring-shaped concave and convex distribution similar to a fingerprint;

[0082] The flexible sensing layer includes a PDMS packaging layer 5 and a micro-nano optical fiber coupler embedded in the PDMS packaging layer;

[0083] The refractive index of PDMS is smaller than that of the micro-nano fiber coupler;

[0084] The fingerprint-like contact layer 4 and the flexible sensing layer are bonded together through PDMS.

[0085] The PDMS cured with a weight ratio of PDMS main agent to curing agent of 20:1 was used as the fingerprint-like contact layer 4 .

[0086] The height of each elliptical ring protrusion in the fingerprint-like contact layer 4 is 1 mm, the width is 2 mm, the distance between the major axis of each adjacent protruding elliptical ring is 2 mm, and the distance between the minor axis is 1 mm.

[0087] The PDMS encapsulation layer 5 is formed by curing PDMS with a weight ratio of PDMS main agent to curing agent of 10:1, and the thickness thereof is 100 μm.

[0088] The Young's modulus of the fingerprint-like contact layer 4 is greater than the Young's modulus of the PDMS encapsulation layer 5 .

[0089] The uniform waist diameter of the micro-nano optical fiber in the micro-nano optical fiber coupler is 3um and the length is 8mm.

[0090] The micro-nano fiber coupler is embedded in the PDMS packaging layer 5 .

[0091] The fingerprint-like contact layer 4 and the flexible sensing layer are bonded together using PDMS with a weight ratio of PDMS main agent to curing agent of 10:1 as an adhesive layer to form the optical fiber bionic sensor 11.

[0092] The ASE broadband light source 10 is directly connected to the micro-nano fiber coupler port I6, the micro-nano fiber coupler port III8 is directly connected to the 50 / 50 fiber coupler 12, the 50 / 50 fiber coupler output port I13 is connected to the spectrum analyzer 15, the 50 / 50 fiber coupler output port II14 is connected to the narrowband bandpass filter 16, the micro-nano fiber coupler port IV9 is directly connected to the narrowband bandpass filter 16, the two output ends of the narrowband bandpass filter 16 are respectively connected to two photodetectors, the two photodetectors are connected to the digital acquisition card 19, and the digital acquisition card 19 is connected to the tactile signal intelligent processing subsystem 20.

[0093] The tactile signals collected by the optical fiber bionic sensor 11 are subjected to wavelet transformation to extract signal features, and then the signals with different features are classified through a machine learning algorithm to establish the database.

[0094] The present invention is based on the following working principle:

[0095] According to the coupling properties of the micro-nano fiber coupler, the output light intensities of its ports III and IV are defined by the following expressions:

[0096]

[0097] Where P1 is the intensity of the input light, l is the coupling length (i.e., the uniform waist length), and c(λ,n2,z) is the coupling coefficient at the coupling position z.

[0098] The coupling in the uniform waist region of the micro-nano fiber coupler can be regarded as a strong coupling between the two micro-nano fibers in the uniform waist region. In the case of strong coupling, the two micro-nano fibers contact and fuse with each other, and the coupling coefficient at position z in the coupling region can be expressed as:

[0099]

[0100] in, is the normalized frequency, r is the radius of the micro-nano fiber in the uniform waist region, λ is the wavelength of the incident light, n2 and n3 are the refractive indices of the fiber and the external environment (PDMS), respectively.

[0101] When the fingerprint-like contact layer 4 comes into contact with the object being measured, the temperature of the object's surface is transferred to the fingerprint-like contact layer 4 and the flexible sensing layer. Due to the large evanescent field of the micro-nano fiber coupler and the large negative thermo-optical coefficient of PDMS, the external refractive index n3 of the micro-nano fiber coupler changes, thereby modulating the wavelength of the optical signal and causing wavelength drift. Temperature is detected by monitoring the drift of characteristic wavelengths (such as peaks or troughs).

[0102] When the fingerprint-like contact layer 4 contacts the object being measured, the resulting pressure is transmitted through the fingerprint-like contact layer 4 to the fingerprint-like sensing layer, ultimately causing radial bending strain in the micro-nano fiber coupler. This results in bending loss, which reduces the output intensities P3 and P4. This in turn achieves a pressure-modulated optical signal intensity that is inversely proportional to the magnitude of the radial bending strain. Because the mechanical hardness of different measured objects varies, objects with greater mechanical hardness will induce greater bending strain in the micro-nano fiber coupler under the same applied pressure, while objects with less mechanical hardness will induce less bending strain. By monitoring the changes in the total output intensity P3 + P4, the magnitude of the bending strain is detected, thereby achieving hardness identification.

[0103] When the fingerprint-like contact layer 4 slides relative to the object being measured, the Young's modulus of the fingerprint-like contact layer 4 is greater than that of the PDMS encapsulation layer 5. This layer converts the sliding friction signal into a vibration signal, causing bending strain in the micro-nano fiber coupler, which in turn modulates the intensity of the optical signal. By monitoring the total output intensity P3 + P4, its amplitude and frequency vary with the surface properties of the object being measured and the sliding friction velocity.

[0104] Using space-division multiplexing technology, a micro-nano fiber coupler couples part of the light input from the light source to another micro-nano fiber. Light output from output port III of the micro-nano fiber coupler enters a 50 / 50 fiber coupler and then enters an optical spectrum analyzer through output port I of the 50 / 50 fiber coupler. Temperature is detected by monitoring the characteristic wavelength shift in its transmission spectrum. Light output from port II of the 50 / 50 fiber coupler 12 enters a narrowband bandpass filter and then a photodetector to detect its intensity P3. Light output from output port IV of the micro-nano fiber coupler is filtered by a narrowband bandpass filter 16 and then enters a photodetector to detect its intensity P4. The tactile signal is then collected by a digital acquisition card and sent to the tactile signal processing system. By detecting the amplitude change of the total intensity P3+P4 of its output light, it is possible to detect whether the object being measured is touched and the softness and hardness of the object being measured; by monitoring the amplitude change and frequency of the total intensity P3+P4 of the output light, the tactile vibration signal caused by sliding friction is detected, and the tactile vibration signal is extracted using wavelet transform. Then, the signals with different characteristics are classified through machine learning algorithms and a database is established. Subsequently, signal feature matching is performed to identify the roughness of the surface of the object being measured.

[0105] like Figure 2 The fiber-optic biomimetic sensor 11 provided in this embodiment comprises, from top to bottom, a fingerprint-like contact layer 4 and a flexible sensing layer. The fingerprint-like contact layer 4 is a concentric elliptical ring-shaped protrusion. The flexible sensing layer includes a PDMS encapsulation layer 5 and an embedded micro-nano fiber coupler. The micro-nano fiber coupler comprises a conventional commercial single-mode fiber 1, a tapered transition region 2 of the micro-nano fiber, and a uniform waist region 3 of the micro-nano fiber. It also has four input and output ports: micro-nano fiber coupler port I 6, micro-nano fiber coupler port II 7, micro-nano fiber coupler port III 8, and micro-nano fiber coupler port IV 9. First, a micro-nano fiber coupler prepared by melt-tapering two conventional commercial single-mode optical fibers 1 entangled with each other is embedded in a degassed PDMS encapsulation layer 5 and then heated and cured to prepare a flexible sensing layer. Secondly, a fingerprint-like contact layer 4 is prepared by mold casting. Then, a layer of PDMS is brushed on the upper surface of the flexible sensing layer, and then the fingerprint-like contact layer 4 is placed horizontally thereon. As the PDMS solidifies, the fingerprint-like contact layer 4 and the flexible sensing layer will be tightly bonded together to prepare a fiber optic bionic sensor.

[0106] The fingerprint-like contact layer 4 is an elliptical ring with a height of 1mm and a width of 2mm. The distance between the major axis and the minor axis of each adjacent elliptical ring is 2mm and 1mm, respectively. It is made of PDMS with a base to curing agent ratio of 20:1 by weight. In the flexible sensing layer, the PDMS encapsulation layer 5 is 100μm thick and made of PDMS with a base to curing agent ratio of 10:1 by weight. In the micro-nano fiber coupler, the uniform waist region 3 of the micro-nano fiber has a diameter of 3μm and a length of 8mm. The micro-nano fiber coupler is formed by twisting two of these micro-nano fibers together, and its primary material is SiO2 (silicon dioxide).

[0107] In this embodiment, the actual preparation method of the fingerprint-like contact layer 4 is as follows: first, a reverse structure mold is designed using computer Solidworks software, and the structure is in the shape of "concentric" elliptical rings, wherein the depth of the depression of each elliptical ring is 1 mm and the width is 2 mm, and the distance between the major axis of each two depressed elliptical rings is 2 mm, and the distance between the minor axis is 1 mm; secondly, the designed mold CAD file is imported into the operating software of the 3D printer, and polytetrafluoroethylene (PTFE) is used as the raw material for 3D printing, and a reverse structure mold is prepared by 3D printing technology; a PDMS solution with a weight ratio of the main agent to the curing agent of 20:1 is prepared, and after sufficient stirring, the air in the PDMS solution is extracted using a vacuum pump to avoid the influence of bubbles; the degassed PDMS solution is poured into the mold, and then heated to 80°C in an incubator and left for 30 minutes to cure; the cured PDMS is separated from the mold to prepare the fingerprint-like contact layer 4. The fingerprint-like contact layer 4 can convert the tactile information interacting with the surface of the measured object into temperature signals, pressure signals and vibration signals.

[0108] In this embodiment, the actual preparation method of the PDMS encapsulation layer 5 is as follows: a PDMS solution with a main agent and a curing agent weight ratio of 10:1 is prepared, and after sufficient stirring, the air in the PDMS solution is extracted using a vacuum pump; the degassed PDMS solution is inverted on the center of the Teflon substrate, and then the PDMS solution is evenly coated on the Teflon substrate using a uniform coating spin coater and its thickness is controlled by setting the spin coating speed and time. In this embodiment, a three-stage spin coating method is adopted, with a spin coating speed of 200 rpm and a time of 20 s in the first stage, a spin coating speed of 500 rpm and a time of 3 s in the second stage, and a spin coating speed of 500 rpm and a time of 3 s in the second stage. 0s, the spin coating speed of the third section is 1000rpm, and the time is 30s, wherein the purpose of the first and second spin coating is to evenly coat the PDMS on the substrate, and the third spin coating reduces the thickness of the PDMS to 50um; the spin-coated PDMS is heated to 80℃ and maintained for 30 minutes to solidify to obtain the bottom layer of the PDMS encapsulation layer 5; the above spin coating operation is repeated on the solidified uniform PDMS film to prepare the top layer of the PDMS encapsulation layer 5, wherein the thickness of the bottom and top layers of the PDMS encapsulation layer 5 are both 50um, that is, the overall thickness of the PDMS encapsulation layer 5 is 100um.

[0109] In this embodiment, the actual preparation method of the micro-nano fiber coupler is as follows: the plastic coating of two conventional commercial single-mode optical fibers at the portion where tapering is required is stripped off to obtain a section of bare optical fiber; the two conventional commercial single-mode optical fibers are intertwined at the exposed portion, and then they are placed on the clamps at both ends of a tapering displacement platform and fixed so that the intertwined bare fiber portions are aligned with the electric heater area; the electric heater is heated to 1300°C to soften the optical fibers, and then the tapering displacement platform is manipulated to perform tapering to prepare the micro-nano fiber coupler. In this embodiment, the uniform waist diameter 3 of each micro-nano optical fiber in the micro-nano fiber coupler is 3 μm and the length is 8 mm.

[0110] In this embodiment, the flexible sensing layer is fabricated as follows: a micro-nano fiber coupler is placed on a PDMS encapsulation layer 5. At this point, the bottom layer of the PDMS encapsulation layer 5 has solidified, while the top layer is still in a liquid state (spin-coated but unsolidified). Due to its own gravity, the micro-nano fiber coupler placed on top naturally embeds itself above the bottom layer and below the top layer of the PDMS encapsulation layer 5. The layer is then heated to 80°C and allowed to stand for 30 minutes to solidify the top layer, thereby fabricating a flexible sensing layer. In the flexible sensing layer, the elasticity and flexibility of PDMS allow the tactile pressure and vibration signals generated by the fingerprint-like contact layer 4 to be transmitted to the micro-nano fiber coupler, generating bending loss and causing changes in its waist diameter and coupling length. Due to the large negative thermo-optical coefficient of PDMS, changes in the sensor's external temperature are converted into changes in the PDMS refractive index, causing a shift in the characteristic wavelength of light in the micro-nano fiber coupler. Due to the high sensitivity, large evanescent field ratio, and strong coupling characteristics of the micro-nano fiber coupler, the biomimetic function of simultaneously sensing temperature and touch is achieved.

[0111] In this embodiment, the actual preparation method of the fiber optic bionic sensor 11 is as follows: a layer of PDMS solution with a thickness of about 5 μm and a main agent to curing agent weight ratio of 10:1 is brushed on the top layer of the PDMS encapsulation layer 5 as an adhesive, and then the fingerprint-like contact layer 4 and the flexible sensing layer are bonded together. Finally, it is heated to 80°C and left for 30 minutes to cure the adhesive, and the fiber optic bionic sensor 11 can be prepared.

[0112] like Figure 3 and Figure 4 The figures show the front and top views of the fiber optic biomimetic sensor 11 of the present invention, respectively. These perspectives provide a more complete and intuitive representation of the three-dimensional structure of the fiber optic biomimetic sensor 11. From top to bottom, the sensor consists of a fingerprint-like contact layer 4 and a flexible sensing layer. The fingerprint-like contact layer 4 is a concentric elliptical ring-shaped protrusion. The flexible sensing layer includes a PDMS encapsulation layer 5 and a micro-nano fiber coupler embedded therein. The micro-nano fiber coupler comprises a conventional commercial single-mode optical fiber 1, a tapered transition region 2 of the micro-nano fiber, and a uniform waist region 3 of the micro-nano fiber. The micro-nano fiber coupler also has four input and output ports: micro-nano fiber coupler port I 6, micro-nano fiber coupler port II 7, micro-nano fiber coupler port III 8, and micro-nano fiber coupler port IV 9.

[0113] like Figure 1As shown, the intelligent bionic sensing system based on fiber optic tactile perception provided by this embodiment includes an ASE wide-spectrum light source 10, a fiber optic bionic sensor 11, a 50 / 50 fiber optic coupler 12, a 50 / 50 fiber optic coupler output port I 13, a 50 / 50 fiber optic coupler output port II 14, a spectrum analyzer 15, a narrowband bandpass filter 16, a first photodetector 17, a second photodetector 18, a digital acquisition card 19, and a tactile signal intelligent processing subsystem 20.

[0114] In this embodiment, the broadband light beam output by the ASE broadband light source 10 passes through a conventional commercial single-mode optical fiber 1 and is input into the optical fiber biomimetic sensor 11 from the micro-nano optical fiber coupler port I6. After being coupled to another micro-nano optical fiber through the uniform waist region 3 of the micro-nano optical fiber, the beam is split into two beams. One beam is output from the micro-nano optical fiber coupler port III8 to the 50 / 50 optical fiber coupler 12 and further split into two beams. The light output from the 50 / 50 optical fiber coupler output port I13 enters the optical spectrum analyzer 15 for monitoring wavelength drift to detect the surface temperature of the object being measured. The other beam output from the 50 / 50 optical fiber coupler output port II14 passes through a narrowband bandpass filter 16 and enters a second photodetector 18 to detect its intensity P3. The other beam output from the micro-nano optical fiber coupler port IV9 enters a narrowband bandpass filter 16 for intensity detection and then passes through a first photodetector 17 to detect its intensity P4. The tactile signal is then collected by a digital acquisition card 19 and sent to the tactile signal intelligent processing subsystem 20 for further signal processing. By monitoring the total output intensity P3+P4 of the fiber optic biomimetic sensor 11, i.e., the sum of the light intensities P3 and P4 output by the fiber optic biomimetic sensor 11 detected by the first photodetector 17 and the second photodetector 18, respectively, the purpose of detecting tactile pressure and tactile vibration can be achieved. In this example, the intelligent biomimetic sensing system based on fiber optic tactile perception utilizes space division multiplexing technology to simultaneously detect the surface temperature of the measured object, the pressure interacting with the measured object, and the vibration caused by sliding friction, thereby simultaneously realizing the temperature and tactile biomimetic functions of human skin.

[0115] Reference Figure 5 As shown, this embodiment provides a process for identifying the surface texture features of the object under test based on tactile perception in the tactile signal intelligent processing subsystem 20, wherein the tactile signal collected by the digital acquisition card is subjected to wavelet transform to extract the frequency features of its vibration signal, and then the different frequency feature signals corresponding to the surface texture features of different objects are classified using a machine learning algorithm and a database is established, and then the obtained tactile signal is subjected to feature extraction and cross-correlation operation with the feature signals in the database to determine whether they match, thereby achieving the purpose of identifying the surface texture features of the object under test.

[0116] The above description is merely a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. Intelligent bionic sensing system based on optical fiber tactile perception, characterized by: Including fiber optic bionic sensor, optical path subsystem and tactile signal intelligent processing subsystem; The optical fiber bionic sensor is used to obtain tactile signals of the object being measured and convert the tactile signals; The optical path subsystem is used to obtain a tactile light signal according to the converted tactile signal, obtain the surface temperature of the measured object according to the tactile light signal, and transmit the tactile light signal to the tactile signal intelligent processing subsystem; The tactile signal intelligent processing subsystem is used to identify the hardness and surface roughness of the object under test according to the tactile light signal; The optical fiber bionic sensor comprises a fingerprint-like contact layer and a flexible sensing layer; The fingerprint-like contact layer is used to obtain the tactile signal and transmit the tactile signal to the flexible sensing layer; the fingerprint-like contact layer is in the form of concentric elliptical ring protrusions; The flexible sensing layer includes a PDMS packaging layer and a micro-nano optical fiber coupler; The PDMS packaging layer is used to transmit the tactile signal to the micro-nano optical fiber coupler; The micro-nano optical fiber coupler includes a micro-nano optical fiber coupler port I, a micro-nano optical fiber coupler port II, a micro-nano optical fiber coupler port III, and a micro-nano optical fiber coupler port IV; The micro-nano optical fiber coupler is used to convert the tactile signal; The tactile signals include temperature signals, pressure signals and vibration signals; The micro-nano optical fiber coupler converts the temperature signal into a characteristic wavelength drift of light in the micro-nano optical fiber coupler; The micro-nano optical fiber coupler converts the pressure signal and the vibration signal into the bending strain of the micro-nano optical fiber coupler; The optical path subsystem includes an ASE broad spectrum light source, a 50 / 50 fiber coupler, a spectrum analyzer, a narrow bandpass filter, a first photodetector, a second photodetector and a digital acquisition card; The ASE broadband light source is connected to the optical fiber bionic sensor via the micro-nano optical fiber coupler port I, and is used to output a broadband light beam to the optical fiber bionic sensor; The 50 / 50 optical fiber coupler is connected to the optical fiber bionic sensor via the micro-nano optical fiber coupler port III; The 50 / 50 fiber coupler includes a 50 / 50 fiber coupler output port I and a 50 / 50 fiber coupler output port II; The spectrum analyzer is connected to the 50 / 50 optical fiber coupler via the 50 / 50 optical fiber coupler output port I, and the spectrum analyzer is used to detect the surface temperature of the object to be measured based on the characteristic wavelength drift of the light; The narrowband bandpass filter is connected to the 50 / 50 optical fiber coupler through the 50 / 50 optical fiber coupler output port II, and the narrowband bandpass filter is also connected to the optical fiber bionic sensor through the micro-nano optical fiber coupler port IV; The narrowband bandpass filter is connected to the digital acquisition card via the first photodetector and the second photodetector, respectively. The digital acquisition card is used to collect the second tactile light signal output by the first photodetector and the first tactile light signal output by the second photodetector, and transmit them to the tactile signal intelligent processing subsystem. The tactile signal intelligent processing subsystem is based on the tactile perception of the surface texture feature recognition process of the measured object. The tactile signal collected by the digital acquisition card is subjected to wavelet transform to extract the frequency characteristics of its vibration signal. Then, the machine learning algorithm is used to classify the different frequency characteristic signals corresponding to the surface texture characteristics of different objects and establish a database. Subsequently, the obtained tactile signal is subjected to feature extraction and cross-correlation operation with the characteristic signals in the database to determine whether they match, thereby achieving the purpose of surface texture feature recognition of the measured object.

2. The intelligent bionic sensing system based on optical fiber tactile perception according to claim 1 is characterized in that: The optical signal path in the optical path subsystem is: The broadband light source outputs a broadband light beam, which is input into the fiber bionic sensor through the micro-nano fiber coupler port I. In the fiber bionic sensor, the broadband light beam is split into a first light beam and a second light beam. The first light beam is output from the micro-nano fiber coupler port III to the 50 / 50 fiber coupler and is further split into a third light beam and a fourth light beam. The third light beam is output through the 50 / 50 fiber coupler output port I and enters the optical spectrum analyzer OSA for detecting the surface temperature of the object under test by monitoring the characteristic wavelength drift. The fourth light beam is output through the 50 / 50 fiber coupler output port II, enters the narrowband bandpass filter, and then enters the second photodetector to obtain the first tactile light signal. The second light beam is output through the micro-nano fiber coupler port IV, enters the narrowband bandpass filter, and then enters the first photodetector to obtain the second tactile light signal. Both the first tactile light signal and the second tactile light signal are collected by the digital acquisition card.

3. The intelligent bionic sensing system based on optical fiber tactile perception according to claim 1 is characterized in that: The method for preparing the fingerprint-like contact layer is as follows: based on PTFE, 3D printing a reverse structure mold, and preparing the fingerprint-like contact layer based on a PDMS solution of a first ratio and the reverse structure mold.

4. The intelligent bionic sensing system based on optical fiber tactile perception according to claim 3 is characterized in that: The PDMS encapsulation layer is prepared by uniformly coating a PDMS solution with a second ratio on a Teflon substrate, spin-coating the PDMS solution using a three-stage spin coating method, and heating and curing the spin-coated PDMS solution to prepare the PDMS encapsulation layer; The method for preparing the micro-nano optical fiber coupler comprises: stripping the plastic coating layer of the tapered portion of two conventional commercial single-mode optical fibers, twisting the exposed portions together, fixing and heating them, and then tapering them to prepare the micro-nano optical fiber coupler; The preparation method of the flexible sensing layer is: embedding the micro-nano optical fiber coupler into the PDMS packaging layer to prepare the flexible sensing layer.

5. The intelligent bionic sensing system based on optical fiber tactile perception according to claim 4 is characterized in that: The preparation method of the optical fiber bionic sensor is as follows: based on the PDMS solution with the second ratio, the fingerprint-like contact layer and the flexible sensing layer are bonded together, and then heated and cured to prepare the optical fiber bionic sensor.

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