Bending sensor and bionic manipulator

Abstract

The sensor comprises a light emitting part, a light guide module, a light mixing module and a light sensing module, the light emitting part is located at one end of the light guide module, and the light mixing module and the light sensing module are sequentially arranged at the other end of the light guide module; the light-emitting part is used for emitting first, second and third light sources; the light guide module comprises a first fiber core layer, a second fiber core layer, a third fiber core layer and an outer cladding layer, and the first fiber core layer, the second fiber core layer and the third fiber core layer are respectively used for conducting the first light source, the second light source and the third light source to correspondingly obtain three types of conduction light; the outer wrapping layer wraps the peripheries of the first fiber core layer, the second fiber core layer and the third fiber core layer; the light mixing module is used for mixing the three kinds of conduction light to obtain mixed light; the light sensing module is used for judging the bending angle and direction of the light guide module according to light intensity attenuation of the three light sources in the mixed light. The sensor can perform omnidirectional bending measurement, and the flexibility of the bionic manipulator integrated with the sensor can be ensured.

Description

Technical Field

[0001] This application relates to the technical field of sensors, and particularly to a bending sensor and a bionic manipulator. Background Art

[0002] The human hand is an extraordinary achievement of human evolution and is famous for its complex morphological features. These features are evident in its precise bone structure, different joint structures, and a closely coordinated control system of nerves and muscles. Therefore, the human hand has a large number of degrees of freedom and a high degree of flexibility, enabling it to perform delicate operation tasks such as medical surgery, industrial assembly, and complex services. In addition, proprioceptors that sense hand postures, including muscle spindles, Golgi tendon organs, and Pacinian corpuscles, are embedded in the tendons and muscles of the human hand. Under the coordinated control of these sensors and nerves, human fingers can move extremely precisely.

[0003] To achieve the dexterous operation performance of the robot end effector approaching the human level, many anthropomorphic manipulator configurations have been developed and introduced successively. Take the bionic dexterous hand of InTime Robotics as an example. It is equipped with six micro linear actuators, two of which are dedicated to controlling the degrees of freedom of the double joints of the thumb, and the remaining four actuators drive the movement of the other four fingers respectively. Although partial motion coordination functions are achieved through a linkage mechanism, its motion mode is still limited to basic grasping forms, such as making a fist and spreading the palm. Another typical representative, the IH2 Azzurra dexterous hand, adopts a five-degree-of-freedom tendon drive structure, and each finger is driven by an independent tendon. The shadow dexterous hand is equipped with 20 DC servo motors to achieve full independent control of the degrees of freedom of each finger joint, thus having the ability to perform complex hand operations. The Hanns dexterous hand integrates a single motor in the palm and constructs an underactuated system with a tendon transmission path, which can simulate human grasping and pinching actions. It is worth noting that although existing manipulators can complete basic operation tasks, they generally lack the unique flexion and extension function of the metacarpophalangeal joint of human fingers, resulting in their difficulty in performing refined operations such as playing the piano, tying shoelaces, and writing with a pen.

[0004] Currently, most humanoid dexterous hands lack the multi-degree-of-freedom proprioceptive ability similar to that of the human hand. In particular, there are significant challenges in the adduction / abduction coordinated control. Among them, the combination of flexible actuators and sensors shows potential, but the existing sensing solutions still have limitations: although optical sensors can detect the overall bending degree through the change of light intensity, they cannot identify the bending direction; resistive sensors can monitor the bending effect of a single degree of freedom well through the change of resistance, but in solutions such as liquid metal strain sensing, the multi-degree-of-freedom composite motion will still produce attitude coupling. To sum up, the current technology is mainly limited to the measurement of single-joint degrees of freedom, and the decoupled perception of flexion and adduction / abduction coordinated motion has not been achieved. Therefore, although there have been studies on adduction / abduction drive mechanisms, humanoid dexterous hand systems with a complete five-finger structure and both abduction / adduction functions are still rare in the existing technology system. Summary of the Invention

[0005] The main technical problem to be solved by this application is to provide a bending sensor and a bionic manipulator, which solve the problem that the existing humanoid dexterous hands are limited to the measurement of a single degree of freedom of the dexterous finger joints and it is difficult to decouple the coordinated motion involving finger flexion and adduction / abduction.

[0006] To solve the above technical problem, a technical solution adopted by this application is to provide a bending sensor, which includes a light-emitting component, a light guiding module, a light mixing module, and a light sensing module. The light-emitting component is located at one end of the light guiding module, and the light mixing module and the light sensing module are arranged in sequence at the other end of the light guiding module; the light-emitting component is used to simultaneously emit a first light source, a second light source, and a third light source; the light guiding module includes a first core layer, a second core layer, a third core layer, and an outer cladding layer. The first core layer, the second core layer, and the third core layer are parallel to each other in pairs. The first core layer, the second core layer, and the third core layer are respectively used to conduct the first light source, the second light source, and the third light source to obtain three kinds of color-conducted lights; the outer cladding layer is wrapped around the periphery of the first core layer, the second core layer, and the third core layer; the light mixing module is used to mix the three kinds of color-conducted lights to obtain mixed light; the light sensing module is used to judge the bending angle and direction of the light guiding module according to the light intensity attenuation of the three light sources in the mixed light.

[0007] This application also provides a bionic manipulator, which includes a palm and a plurality of fingers connected to the palm. The above-mentioned bending sensor is arranged in the palm and the fingers to detect the posture angle of the fingers.

[0008] The beneficial effects of the present application are as follows: The present application discloses a bending sensor and a bionic manipulator. The bending sensor includes a light-emitting component, a light guiding module, a light mixing module, and a light sensing module. The light-emitting component is located at one end of the light guiding module, and the light mixing module and the light sensing module are arranged in sequence at the other end of the light guiding module. The light-emitting component is used to simultaneously emit a first light source, a second light source, and a third light source. The light guiding module includes a first core layer, a second core layer, a third core layer, and an outer cladding. The first core layer, the second core layer, and the third core layer are parallel to each other in pairs. The first core layer, the second core layer, and the third core layer are respectively used to conduct the first light source, the second light source, and the third light source, and three kinds of color-conducted lights are correspondingly obtained. The outer cladding is wrapped around the periphery of the first core layer, the second core layer, and the third core layer. The light mixing module is used to mix the three kinds of color-conducted lights to obtain mixed light. The light sensing module is used to judge the bending angle and direction of the light guiding module according to the light intensity attenuation of the three light sources in the mixed light. This bending sensor exhibits good measurement performance, as well as stability and repeatability in multiple degrees of freedom, and its sensing ability effectively meets the attitude sensing requirements of the bionic manipulator for performing multi-degree-of-freedom operation tasks. Description of the Drawings

[0009] Figure 1 is a schematic diagram of the overall structure of an embodiment of a bending sensor according to the present application;

[0010] Figure 2 is a schematic diagram of the optical path principle in the non-bending state of an embodiment of a bending sensor according to the present application;

[0011] Figure 3 is a schematic diagram of the optical path principle in the bending state of an embodiment of a bending sensor according to the present application;

[0012] Figure 4 is a graph showing the change trends of the light intensity attenuation of red light, green light, and blue light and the different strains of the corresponding core layers in the core layers of a bending sensor according to the present application with 2, 3, 6, and 9 short optical fiber segments respectively;

[0013] Figure 5 is a schematic diagram of a spatial rectangular coordinate system established with one end of a bending sensor as the origin according to an embodiment of the present application;

[0014] Figure 6 is a cross-sectional view of the light-emitting component in an embodiment of a bending sensor according to the present application;

[0015] Figure 7 is a schematic diagram of the structure of an embodiment of a bionic manipulator according to the present application;

[0016] Figure 8 is a schematic diagram of the specific structure of an embodiment of a bionic manipulator according to the present application;

[0017] Figure 9 It is a schematic diagram of the specific structure of a finger in an embodiment of a bionic manipulator according to the present application;

[0018] Figure 10 It is a schematic diagram of the working principle of an embodiment of a bionic manipulator according to the present application;

[0019] Figure 11 It is a diagram showing the change in light intensity attenuation collected during 100 cycles of reciprocating stretching at a strain of 10% in an embodiment of a bending sensor according to the present application;

[0020] Figure 12 It is a schematic diagram showing the change in light intensity attenuation over time at different strain levels in an embodiment of a bending sensor according to the present application;

[0021] Figure 13 It is a schematic diagram showing the change in light intensity attenuation under different radial pressures in an embodiment of a bending sensor according to the present application;

[0022] Figure 14 It is a schematic diagram showing the change in light intensity attenuation at different strain levels in an embodiment of a bending sensor according to the present application;

[0023] Figure 15 It is a schematic diagram showing the relationship between the strain of the short optical fiber segments of the three core layers and the pitch angle during the pitching process in an embodiment of a bending sensor according to the present application;

[0024] Figure 16 It is a schematic diagram showing the relationship between the strain of the short optical fiber segments of the three core layers and the yaw angle during the yaw bending process in an embodiment of a bending sensor according to the present application;

[0025] Figure 17 It is a schematic diagram showing the influence of the short optical fiber segments of the three core layers on the light intensity attenuation during the pitching process in an embodiment of a bending sensor according to the present application;

[0026] Figure 18 It is a schematic diagram showing the influence of the short optical fiber segments of the three core layers on the light intensity attenuation during the yaw bending process in an embodiment of a bending sensor according to the present application;

[0027] Figure 19 It is a schematic diagram showing the result of comparing the calculated true pitch angle with the theoretical pitch angle in an embodiment of a bending sensor according to the present application;

[0028] Figure 20 It is a schematic diagram showing the result of comparing the calculated true yaw angle with the theoretical yaw angle in an embodiment of a bending sensor according to the present application;

[0029] Figure 21It is a schematic diagram of the change over time of the bending angle of the index finger and the light intensity attenuation of the light conducted by the three fiber core layers in the corresponding bending sensor during the process of using scissors in an embodiment of a bionic manipulator according to the present application, and the corresponding color coordinate diagram;

[0030] Figure 22 It is a schematic diagram of the change over time of the bending angle of the index finger and the light intensity attenuation of the light conducted by the three fiber core layers in the corresponding bending sensor during the process of operating a mouse in an embodiment of a bionic manipulator according to the present application, and the corresponding color coordinate diagram;

[0031] Figure 23 It is a color coordinate diagram corresponding to the index finger, middle finger, ring finger and little finger during the process of playing the piano in an embodiment of a bionic manipulator according to the present application, and a schematic diagram of the change over time of the bending angle of each finger and the light intensity attenuation of the light conducted by the three fiber core layers in the corresponding bending sensor. Detailed implementation manners

[0032] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present application.

[0033] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly disposed on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component.

[0034] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0035] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, the meaning of "a plurality" and "several" is two or more, unless otherwise specifically defined.

[0036] It should be noted that the structures, ratios, sizes, etc. shown in the attached drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the implementation conditions of this application. Therefore, they do not have any substantial technical significance. Any modification of the structure, change in the ratio relationship, or adjustment of the size, without affecting the effects that this application can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in this application.

[0037] Figure 1 An embodiment of a bending sensor of this application is shown, including a light-emitting component 1, a light guiding module 2, a light mixing module 3, and a light sensing module 4. The light-emitting component 1 is located at one end of the light guiding module 2, and the light mixing module 3 and the light sensing module 4 are arranged in sequence at the other end of the light guiding module 2.

[0038] Combined with Figure 2 , the light-emitting component 1 is used to simultaneously emit a first light source, a second light source, and a third light source; the light guiding module 2 includes a first core layer 21, a second core layer 22, a third core layer 23, and an outer cladding layer 24. The first core layer 21, the second core layer 22, and the third core layer 23 are pairwise parallel. The first core layer 21, the second core layer 22, and the third core layer 23 are respectively used to conduct the first light source, the second light source, and the third light source, and correspondingly obtain three colors of transmitted light; the outer cladding layer 24 is wrapped around the peripheries of the first core layer 21, the second core layer 22, and the third core layer 23; the light mixing module 3 is used to mix the three colors of transmitted light to obtain mixed light; the light sensing module 4 is used to judge the bending angle and direction of the light guiding module 2 according to the light intensity attenuation of the three light sources in the mixed light.

[0039] Combined with Figure 2 and Figure 3 , the light-emitting component 1 uses a three-color LED, and the three-color LED can simultaneously emit a first light source, a second light source, and a third light source. These three colors of light sources are respectively input into the first core layer 21, the second core layer 22, and the third core layer 23 for conduction to obtain three colors of transmitted light. Furthermore, the light mixing module 3 mixes the three colors of transmitted light to obtain mixed light, so that the light sensing module 4 judges the bending angle and direction of the light guiding module 2 according to the light intensity attenuation of the three colors of light sources in the mixed light.

[0040] In this embodiment, the first light source is red light, and the corresponding wavelength range is distributed between 610 nm and 620 nm; the second light source is green light, and the corresponding wavelength range is distributed between 520 nm and 535 nm; the third light source is blue light, and the corresponding wavelength range is distributed between 465 nm and 480 nm.

[0041] In some other embodiments, light sources of other colors may also be used. For example, yellow light, purple light, etc. As long as the colors of the first light source, the second light source, and the third light source are different, and the corresponding wavelength distributions are within the wavelength ranges of the lights of the corresponding colors.

[0042] As Figure 1 and Figure 2 shown, the first core layer 21, the second core layer 22, and the third core layer 23 each include a plurality of short optical fiber segments 20 that are arranged side by side, have the same size, and have the same spacing distance.

[0043] As Figure 1 shown, the light guiding module 2 is a horizontally placed cylinder. At this time, the length L of the obtained light guiding module is 150 mm, and the cross-sectional diameter is 20 mm. The first core layer 21, the second core layer 22, and the third core layer 23 have the same size. Among them, the length L is 150 mm, and the cross-sectional diameter is 2 mm. The short optical fiber segments 20 in different core layers have the same size. Among them, the length l is 4 mm, and the cross-sectional diameter is 2 mm; and within one core layer, the spacing distance d between two adjacent short optical fiber segments 20 is 0.5 mm.

[0044] In some other embodiments, generally, the length L of the obtained light guiding module 2 is between 50 mm and 200 mm, and the cross-sectional diameter is between 5 mm and 20 mm; the length L of the first core layer 21, the second core layer 22, and the third core layer 23 is between 50 mm and 200 mm, and the cross-sectional diameter is between 1.5 and 6 mm; the length l of the short optical fiber segments 20 in different core layers is between 2 mm and 7 mm, and the cross-sectional diameter is between 1.5 and 6 mm, and within one core layer, the spacing distance d between two adjacent short optical fiber segments 20 is between 0.3 mm and 0.7 mm. It may also be other sizes, as long as the sizes of each part of the bending sensor meet the actual usage requirements.

[0045] It should be noted that the first core layer 21, the second core layer 22, and the third core layer 23 all use PMMA optical fibers. PMMA optical fibers have the characteristics of high refractive index and low optical loss, resulting in negligible attenuation of light intensity during short-distance propagation. Therefore, the sensor experiences insignificant optical bending loss, leading to a decrease in the sensitivity of the sensor. In addition, when the sensor is bent, the mismatch in elastic modulus between the PMMA optical fiber and the elastic outer cladding 24 easily causes stress concentration in the PMMA optical fiber, increasing the possibility of microcrack formation or fiber breakage. To alleviate these challenges, the present application divides the PMMA optical fiber into several short fiber segments 20 to fill the outer cladding 24 of the sensor, thereby significantly increasing the macroscopic bending loss rate of the PMMA optical fiber and alleviating the internal residual stress.

[0046] As Figure 4 shown, it shows the correlation between the number of short fiber segments 20 in the bending sensor and the attenuation of light intensity under different stretching conditions. Under different stretching conditions, the changing trends of the attenuation of the light intensity of red light, green light, and blue light are compared in the core layers with 2, 3, 6, and 9 short fiber segments 20 when the strain of the corresponding core layer gradually increases. Among them, the R-channel attenuation represents the attenuation of the light intensity of red light in the first core layer 21, the G-channel attenuation represents the attenuation of the light intensity of green light in the second core layer 22, and the B-channel attenuation represents the attenuation of the light intensity of blue light in the third core layer 23. It can be seen that an increase in the number of short fiber segments 20 in each core layer of the bending sensor will lead to a decrease in the attenuation of light intensity. At the same time, in the bending sensor with 6 short fiber segments 20, the attenuation of the light intensity corresponding to red light, green light, and blue light is more uniform.

[0047] In some embodiments, the first core layer 21, the second core layer 22, and the third core layer 23 all include 6 short fiber segments 20, which can enhance the uniformity of the measurement factor (GF) of the intensities of red light, green light, and blue light and prevent the decrease in the attenuation of light intensity caused by an excessive number of short fiber segments 20.

[0048] As Figure 2 shown, when the light guiding module 2 is in a non-bent state, the light sources of the three colors emitted by the light emitting member 1 are respectively input from one end of the first core layer 21, the second core layer 22, and the third core layer 23, and propagate through total internal reflection in the first core layer 21, the second core layer 22, and the third core layer 23 to obtain the transmitted light of the three colors; then, the transmitted light of the three colors is respectively output from the other end of the first core layer 21, the second core layer 22, and the third core layer 23, and the transmitted light of the three colors is mixed by the mixing module 3 to obtain the mixed light. Finally, the photosensitive module 4 can determine the intensities of the light of three different wavelengths within the spectrum according to the mixed light.

[0049] It should be noted that the attenuation of light in a medium can be expressed as:

[0050] ;

[0051] wherein, and respectively represent the input and output light intensities; e represents the natural logarithm; and respectively represent the absorption coefficient and the optical path of the medium. Therefore, the intensity of the light emitted from the end of the light guiding module 2 (the end close to the light mixing module 2) can be expressed by the first formula:

[0052] ;

[0053] wherein, n is the total number of short optical fiber segments 20 included in the bending sensor; represents the absorption coefficient of the PMMA optical fiber; represents the absorption coefficient of the air between two adjacent short optical fiber segments 20 in the same core layer; l represents the length of each short optical fiber segment 20; d represents the interval distance between two adjacent short optical fiber segments 20. The corresponding light intensity attenuation can be expressed by the second formula:

[0054] .

[0055] Furthermore, substituting the first formula into the second formula , the relationship between the light intensity attenuation and the length of the short optical fiber segment, as well as the interval distance between two adjacent short optical fiber segments 20 in the same core layer can be obtained as:

[0056] .

[0057] Combined with Figure 3 , when the bending sensor is bent, the first core layer 21 guiding the red light is subjected to tensile stress. This stress causes the interval distance between two adjacent short optical fiber segments 20 in the first core layer 21 to increase , thereby resulting in an increase in light intensity attenuation. On the other hand, the third core layer 23 guiding the blue light is located inside the sensor and experiences compressive stress, causing the interval distance between two adjacent short optical fiber segments 20 in the third core layer 23 to decrease . Therefore, the optical path length within each core layer is changed, resulting in a change in the intensity of the composite spectrum of light of each unique wavelength.

[0058] As Figure 5 shown, in order to determine the bending angle and direction of the bending sensor through the change in light intensity attenuation, the present application establishes a spatial rectangular coordinate system {O} for the bending sensor. The pitch angle and yaw angle shown in the figure represent the bending angles in the corresponding directions of the bending sensor, wherein, represents the angular range of the pitch angle; The angle range of the yaw angle is shown. According to the pitch angle and yaw angle, the accurate bending angle and bending direction of the bending sensor can be obtained.

[0059] It should be noted that, assuming that one end of the bending sensor remains fixed and the other end can be bent in any direction, the strain generated by the short optical fiber segment 20 at its respective cross-sectional position is proportional to the distance from the center point of the short optical fiber segment 20 to the neutral axis, that is, the strain of the short optical fiber segment 20 can be expressed as:

[0060] ;

[0061] in, represents the extension amount of the short optical fiber segment 20; L represents the original length of the short optical fiber segment 20.

[0062] like Figure 6 As shown, the first light source, the second light source and the third light source are arranged on the circumference. Arranged at intervals to form an equilateral triangle layout. Correspondingly, the first core layer 21, the second core layer 22 and the third core layer 23 are also arranged in an equilateral triangle layout on the corresponding cross section. Wherein, R0 represents the center point of the first light source / corresponding short fiber segment 20, G0 represents the center point of the second light source / corresponding short fiber segment 20, and B0 represents the center point of the third light source / corresponding short fiber segment 20; s represents the distance from the center point of the first light source / the second light source / the third light source to the center O of the cross section, that is, the distance from the center point of each short fiber segment 20 on the cross section to the neutral axis; point R d , G d and B d Respectively represent the projection points of points R0, G0 and B0 onto the curved plane.

[0063] Further, when the bending sensor is bent along the bending plane, the strain of each short optical fiber segment 20 in the first core layer 21, the second core layer 22 and the third core layer 23 can be expressed as:

[0064]

[0065] in, represents the strain of the short fiber segment of the first core layer 21; represents the strain of the short fiber segment of the second core layer 22; represents the strain of the short optical fiber segment of the third core layer 23; , and Respectively represent the original lengths of the short optical fiber segments 20 in the first core layer 21, the second core layer 22 and the third core layer 23; , and respectively represent the extension amounts of the short optical fiber segments in the first core layer 21, the second core layer 22, and the third core layer 23; r represents the bending radius of the bending sensor; s represents the distance from the center point of each short optical fiber segment 20 to the neutral axis in the cross-section; θ represents the angle between the cross-section of each short optical fiber segment 20 and the bending plane.

[0066] In this embodiment, .

[0067] Furthermore, the light mixing module 3 uses a light mixing plate, and the photosensitive module 4 is a PCB board. A chromaticity detection chip 40 is provided on the PCB board, and the chromaticity detection chip 40 uses the chip TCS3472 to measure the light intensity attenuation of each color of light to calculate the bending angle and bending direction of the bending sensor.

[0068] Furthermore, the strain and light intensity mapping relationships of the short optical fiber segments 20 in the first core layer 21, the second core layer 22, and the third core layer 23 can be expressed as:

[0069] ;

[0070] Among them, , and respectively represent the calibration coefficients of the first core layer 21, the second core layer 22, and the third core layer 23; , and respectively represent the light intensity attenuations of the three light sources conducted through the first core layer 21, the second core layer 22, and the third core layer 23; , and respectively represent the compensation coefficients of the first core layer 21, the second core layer 22, and the third core layer 23.

[0071] Furthermore, in the photosensitive module 4, the bending angle and direction of the bending sensor are obtained according to the calculation formulas of the pitch angle and the yaw angle; among them, the calculation formulas of the pitch angle and the yaw angle are respectively:

[0072]

[0073] Among them, P represents the pitch angle of the bending sensor; Y represents the yaw angle of the bending sensor.

[0074] Such as Figure 11As shown, the data of the light intensity attenuation changes of three light sources collected during 100 cycles of reciprocating stretching at a strain of 10% are presented. It can be seen that a detailed view of the light intensity attenuation changes of the three light sources in the initial and last 3 cycles is provided. Among them, the red curve represents the light intensity attenuation change of red light; the green curve represents the light intensity attenuation change of green light; the blue curve represents the light intensity attenuation change of blue light. In the initial 3 cycles and the last 3 cycles, the root mean square errors (RMSEs) of the three light source channels are 2.1% (R channel), 1.9% (G channel), and 3.2% (B channel), respectively. The results show that the bending sensor has high repeatability and performance consistency.

[0075] As Figure 12 shown, the step response evaluations at strains of 0.25%, 0.5%, 1%, 2.5%, 5%, and 10% are presented. The bending sensor can detect strains up to 2.5%, indicating its strong tensile response.

[0076] As Figure 13 shown, the sensitivity of the proposed bending sensor to radial compression is presented. Among them, during the bending of the bending sensor, a radial pressure from 0 N to 50 N is applied using a standard force sensor. It can be seen that the bending sensor can maintain a stable output response when the radial pressure is below 10 N.

[0077] As Figure 14 shown, Figures (i) to (vi) illustrate the hysteresis response characteristics of the proposed bending sensor at different strain levels. When the strains are 0.25%, 0.5%, 1%, 2.5%, 5%, and 10%, the corresponding hysteresis coefficients are shown in Table 1.

[0078] Table 1. Hysteresis coefficients of each core layer in the bending sensor under different strain conditions

[0079] Strain (%) R Channel (%) G Channel (%) B Channel (%) 0.25% 11.95% 6.27% 7.09% 0.5% 9.30% 7.91% 2.97% 1% 3.85% 4.68% 5.51% 2.5% 3.41% 3.53% 3.28% 5% 2.57% 5.76% 4.57% 10% 7.73% 3.36% 4.41%

[0080] As Figure 15 and Figure 16As shown, the relationships between the strains of the short optical fiber segments in the three fiber core layers during pitching and yaw bending processes and the theoretical pitching angle and theoretical yaw angle are respectively shown. Among them, the strains of the short optical fiber segments in the three fiber core layers inside the bending sensor are obtained using ANSYS software under ±90° pitching and ±90° yaw. Subsequently, the corresponding theoretical pitching angle and theoretical yaw angle are calculated based on the strain data. It can be seen that during the pitching process, the short optical fiber segments of the second fiber core layer (G channel) and the third fiber core layer (B channel) both exhibit equal strains, while the short optical fiber segment of the first fiber core layer (R channel) shows slightly higher strain. On the contrary, during the yaw bending process, the short optical fiber segments of the second fiber core layer (G channel) and the third fiber core layer (B channel) show equivalent strains, which are higher than the strain of the short optical fiber segment of the first fiber core layer (R channel).

[0081] As Figure 17 and Figure 18 shown, the effects of the short optical fiber segments in the three fiber core layers on the light intensity attenuation during the pitching process and the yaw bending process are respectively shown. Among them, during the pitching process, the attenuation rate of the short optical fiber segment of the first fiber core layer (R channel) is slightly higher than that of the short optical fiber segments of the second fiber core layer (G channel) and the third fiber core layer (B channel). During the yaw bending process, the attenuation of the short optical fiber segment of the first fiber core layer (R channel) is lower than that of the short optical fiber segments of the second fiber core layer (G channel) and the third fiber core layer (B channel), and the short optical fiber segments of the second fiber core layer (G channel) and the third fiber core layer (B channel) show a consistent attenuation trend. It can be seen that the light intensity attenuation trend is consistent with the strain pattern determined in the simulation results, thus verifying the feasibility of calculating the finger posture based on the light intensity attenuation.

[0082] As Figure 19 and Figure 20 shown, the results of using the theoretical pitching angle and theoretical yaw angle of the inertial measurement unit (IMU) as reference attitude parameters and comparing them with the calculated pitching angle and calculated yaw angle calculated by this bending sensor are respectively shown. The average pitching measurement error of the bending sensor is ±2.13°, and the average yaw measurement error is ±2.34°. These results indicate that this bending sensor has good measurement capabilities and is suitable for tasks that require sensing the multi-degree-of-freedom finger posture.

[0083] Based on a unified inventive concept, as Figure 7 shown, this application also provides a bionic manipulator, including a palm 10, a plurality of fingers 20 connected to the palm 10, and the bending sensor as described above is arranged inside the palm 10 and the fingers 20 for detecting the posture angle of the fingers 20.

[0084] Among them, L DIP represents the distal interphalangeal joint of the little finger, L PIP represents the proximal interphalangeal joint of the little finger, L MCP represents the metacarpophalangeal joint of the little finger, LABD Indicates the joint degrees of freedom for the abduction / adduction movement of the little finger; R DIP Indicates the distal phalanx joint of the ring finger, R PIP Indicates the proximal phalanx joint of the ring finger, R MCP Indicates the metacarpophalangeal joint of the ring finger, R ABD Indicates the joint degrees of freedom for the abduction / adduction movement of the ring finger; M DIP Indicates the distal phalanx joint of the middle finger, M PIP Indicates the proximal phalanx joint of the middle finger, M MCP Indicates the metacarpophalangeal joint of the middle finger, M ABD Indicates the joint degrees of freedom for the abduction / adduction movement of the middle finger; I DIP Indicates the distal phalanx joint of the index finger, I PIP Indicates the proximal phalanx joint of the index finger, I MCP Indicates the metacarpophalangeal joint of the index finger, I ABD Indicates the joint degrees of freedom for the abduction / adduction movement of the index finger; T IP Indicates the thumb joint of the thumb, T MCP Indicates the metacarpophalangeal joint of the thumb, I ROT Indicates the joint degrees of freedom for the abduction / adduction movement of the thumb.

[0085] As Figure 8 and Figure 9 shown, the light-emitting member 1 is disposed between the fingertip 201 and the distal phalanx 202 of the finger 20, the light guide module 2 is integrated in the distal phalanx 202 and the proximal phalanx 203 of the finger 20, and the light mixing module 3 and the photosensitive module 4 are fixed on the palm 10.

[0086] Among them, the palm 10 is made by using 3D printing technology, and parts such as the fingertip 201, the distal phalanx 202, the proximal phalanx 203, the distal phalanx joint 204, the proximal phalanx joint 205, and the metacarpophalangeal joint 206 of the finger 20 are also made by using 3D printing technology. Furthermore, the light guide module 2 of a bending sensor can be integrated into the distal phalanx 202 and the proximal phalanx 203 by one-time molding technology, and the corresponding three-color LED is embedded in the fingertip 201. At the same time, the corresponding light mixing plate and the chromaticity detection chip 40 are installed on the palm 10.

[0087] In this embodiment, each finger 20 is designed by a combination of rigid and flexible materials, which can ensure the mobility and flexibility of the joints. Except for the thumb having two degrees of freedom, the other four fingers 20 each have four degrees of freedom. This structure enables each finger 20 to independently perform flexion, abduction, and adduction movements, thereby facilitating the execution of complex and delicate actions.

[0088] Furthermore, in order to enable the finger 20 to flex, abduct, and adduct, the movement of the finger 20 is controlled by a tendon drive mechanism.

[0089] As Figure 8 shown, based on the tendon drive principle of the human hand, nine servo motors 5 are installed on the arm of the bionic manipulator, and the flexion, adduction, and abduction of the finger 20 are achieved through tendon tension.

[0090] As Figure 9 shown, the flexion-extension tendon cord 207 is anchored to the fingertip 201 to facilitate the flexion and extension of the finger 20. The abduction-adduction tendon cord 208 is fixed to the proximal phalanx 203 to control the abduction and adduction of the finger 20. The flexion-extension tendon cord 207 and the abduction-adduction tendon cord 208 are respectively controlled by two groups of servo motors, namely the flexion-extension servo motor 51 and the abduction-adduction servo motor 52.

[0091] Combined with Figure 10 shown, due to the insufficient drive design of the finger 20, when the flexion-extension servo motor 51 drives the pulley, the inner flexion-extension tendon cord 207 is tightened, while the outer one is slack. Therefore, the distal phalanx 202 and the proximal phalanx 203 can bend naturally, mimicking the movement of the human hand. Similarly, the abduction-adduction servo motor 52 controls the tension of the abduction-adduction tendon cord 208 by driving the pulley to achieve the abduction and adduction of the metacarpophalangeal joint 206.

[0092] In this embodiment, each finger 20 integrates an all-round bending sensor as described above to detect the posture angle of the finger, including the pitch angle of the finger 20 flexion and the yaw angle of the abduction-adduction. This design method not only ensures the flexibility and compliance of the finger 20, but also provides two degrees of freedom for the metacarpophalangeal joint 206. Therefore, each metacarpophalangeal joint 206 of the finger 20 has two degrees of freedom, enabling the finger 20 to independently perform abduction, adduction, flexion movements, and complex coordinated movements.

[0093] As Figure 21 shown, it shows the variation of the bending angle of the index finger and the light intensity attenuation of the light conducted by the three fiber core layers in the corresponding bending sensor over time during the process of the bionic manipulator using scissors. In this task, the flexion control is achieved by bending the index finger. The target pitch angle is input into the control system, and the bending sensor provides real-time feedback on the finger posture during the bending process. This enables the accurate achievement of the target angle through a closed-loop control strategy. Due to the tension exerted on the finger by the tendon cord, there is a certain degree of lag in the finger bending movement driven by the servo motor corresponding to the tendon cord. In addition, the sensor data from the index finger is intuitively represented by the color coordinates on the right side of the figure. It can be seen that during the bending process, the blue and green lights significantly attenuate, causing the color coordinates to shift towards the red region.

[0094] AsFigure 22 As shown, it shows the changes in the bending angle of the index finger and the light intensity attenuation of the light conducted by the three core layers in the corresponding bending sensor over time during the operation of the bionic manipulator on the mouse. First, starting from the bending of the index finger, the left mouse button is clicked, and then the index finger moves inwards and bends to click the middle mouse button. When clicking the left and middle mouse buttons, the obvious trajectory changes of the bionic manipulator can be clearly identified through the color coordinates on the right side of the figure.

[0095] As Figure 23 shown, the left side of the figure shows the color coordinate diagrams corresponding to the index finger, middle finger, ring finger, and little finger during the process of the bionic manipulator playing the piano, and the right side of the figure shows the changes in the bending angles of each finger and the light intensity attenuation of the light conducted by the three core layers in the corresponding bending sensor over time. Among them, the color coordinates of each finger visually represent the color data from the corresponding bending sensor. Each finger has a specific note on the piano, except for the little finger, which plays two notes in sequence through adduction and abduction movements. Since playing the piano requires a relatively small finger flexion amplitude, there is a strong correlation between the target angle input to the control system and the angle reported by the bending sensor.

[0096] It can be seen from this that the present application discloses a bending sensor and a bionic manipulator, including a light-emitting component, a light-guiding module, a light-mixing module, and a light-sensing module. The light-emitting component is located at one end of the light-guiding module, and the light-mixing module and the light-sensing module are arranged in sequence at the other end of the light-guiding module; the light-emitting component is used to simultaneously emit a first light source, a second light source, and a third light source; the light-guiding module includes a first core layer, a second core layer, a third core layer, and an outer cladding. The first core layer, the second core layer, and the third core layer are parallel to each other in pairs. The first core layer, the second core layer, and the third core layer are respectively used to conduct the first light source, the second light source, and the third light source, and correspondingly obtain three colors of transmitted light; the outer cladding is wrapped around the periphery of the first core layer, the second core layer, and the third core layer; the light-mixing module is used to mix the three colors of transmitted light to obtain mixed light; the light-sensing module is used to judge the bending angle and direction of the light-guiding module according to the light intensity attenuation of the three light sources in the mixed light. The bending sensor exhibits good measurement performance, as well as stability and repeatability in multiple degrees of freedom, and its sensing ability effectively meets the attitude sensing requirements of the bionic manipulator for performing multi-degree-of-freedom operation tasks.

[0097] The above are only embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present application by the same token.

Claims

1. A bending sensor, characterized in that, It includes a light-emitting component, a light guide module, a light mixing module, and a light-sensing module. The light-emitting component is located at one end of the light guide module, and the light mixing module and the light-sensing module are arranged in sequence at the other end of the light guide module. The light-emitting component is used to emit a first light source, a second light source, and a third light source simultaneously. The light guide module includes a first core layer, a second core layer, a third core layer, and an outer cladding. The first core layer, the second core layer, and the third core layer are parallel to each other in pairs. The first core layer, the second core layer, and the third core layer are respectively used to conduct the first light source, the second light source, and the third light source, and correspondingly obtain three colors of transmitted light. The outer cladding is wrapped around the periphery of the first core layer, the second core layer, and the third core layer. The light mixing module is used to mix the three colors of transmitted light to obtain mixed light. The light-sensing module is used to judge the bending angle and direction of the light guide module according to the light intensity attenuation of the three light sources in the mixed light.

2. The bending sensor according to claim 1, wherein The first core layer, the second core layer, and the third core layer each include a plurality of short optical fiber segments arranged side by side, having the same size and the same spacing distance.

3. The bending sensor according to claim 1, wherein The first light source, the second light source, and the third light source are arranged at 120° intervals on the circumference to form an equilateral triangle layout.

4. The bending sensor according to claim 2, wherein, When the bending sensor is bent along the bending plane, the strains of the short optical fiber segments of the first core layer, the second core layer, and the third core layer are respectively: Among them, represents the strain of the short optical fiber segment of the first core layer; represents the strain of the short optical fiber segment of the second core layer; represents the strain of the short optical fiber segment of the third core layer; , and respectively represent the original lengths of the short optical fiber segments of the first core layer, the second core layer, and the third core layer; , and respectively represent the extension amounts of the short optical fiber segments of the first core layer, the second core layer, and the third core layer; r represents the bending radius of the bending sensor; s represents the distance from the center point of each short optical fiber segment on the cross-section to the neutral axis; θ represents the angle between the cross-section of each short optical fiber segment and the bending plane.

5. The bending sensor according to claim 4, wherein The strain and light intensity mapping relationship of the short optical fiber segments of the first core layer, the second core layer, and the third core layer are expressed as: ； Among them, , and respectively represent the calibration coefficients of the first core layer, the second core layer, and the third core layer; , and respectively represent the attenuation of the light intensities of three light sources conducted through the first core layer, the second core layer, and the third core layer; , and respectively represent the compensation coefficients of the first core layer, the second core layer, and the third core layer.

6. The bending sensor according to claim 5, wherein, In the light-sensing module, according to the calculation formulas of the pitch angle and the yaw angle, the bending angle and direction of the bending sensor are obtained. Among them, the calculation formulas of the pitch angle and the yaw angle are respectively: Among them, P represents the pitch angle of the bending sensor; Y represents the yaw angle of the bending sensor.

7. The bending sensor according to claim 1, wherein The first light source is red light with a wavelength between 610 nm and 620 nm, the second light source is green light with a wavelength between 520 nm and 535 nm, and the third light source is blue light with a wavelength between 465 nm and 480 nm.

8. The bending sensor according to claim 2, wherein The length of the light guide module is between 50 mm and 200 mm, and the cross-sectional diameter is between 5 mm and 20 mm. The first core layer, the second core layer, and the third core layer have the same size, wherein the length is between 50 mm and 200 mm, and the cross-sectional diameter is between 1.5 and 6 mm. The length of the short optical fiber segment is between 2 mm and 7 mm, the cross-sectional diameter is between 1.5 and 6 mm, and the spacing distance between two adjacent short optical fiber segments is between 0.3 mm and 0.7 mm.

9. A bionic manipulator, characterized in that, It includes a palm and a plurality of fingers connected to the palm. The palm and the fingers are provided with the bending sensor according to any one of claims 1-8 for detecting the posture angle of the fingers.

10. The bionic manipulator according to claim 9, wherein The light-emitting component is arranged between the fingertip and the distal phalanx of the finger; the light guide module is integrated in the distal phalanx and the proximal phalanx of the finger; the light mixing module and the light-sensing module are fixed in the palm.

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