A multi-dimensional force sensing device and method for robot fingers based on fiber grating

Abstract

The present invention relates to a multi-dimensional force sensing device and method for robot fingers based on fiber grating, comprising a finger housing, a multi-dimensional force sensor arranged inside the finger housing, the multi-dimensional force sensor comprising a plurality of gratings and a first cantilever beam, a second cantilever beam and a third cantilever beam for deforming with the external force of the finger housing, the first cantilever beam and the second cantilever beam being arranged in the same plane, the third cantilever beam being perpendicular to the plane where the first cantilever beam and the second cantilever beam are located, a plurality of gratings are arranged on the surfaces of the first cantilever beam, the second cantilever beam and the third cantilever beam, and a plurality of gratings are connected to an optical detection system for measuring multi-dimensional force. The present invention has cantilever beams arranged in the directions of the X, Y and Z axes and gratings arranged thereon, by applying force to the finger housing, utilizing the phenomenon of the change in the central wavelength of the reflected light of the grating under force, the magnitude and direction of the multi-dimensional force on the finger housing are calculated, the device has a simple structure, high sensitivity and is easy to maintain.

Description

Technical Field

[0001] The present invention relates to the field of optical sensor measurement of multi-dimensional force, and in particular to a multi-dimensional force sensing device and method for robot fingers based on optical fiber grating. Background Art

[0002] Sensors are a key part of robot control and feedback research. Force sensors are widely used in the field of robotics as a key sensor. In the mechanical sensing and feedback analysis of robot wrists, arms, fingers and other structures, it is often necessary to measure the multi-dimensional force changes between structures and their contact with the external environment, and perceive the characteristics of environmental forces. Traditional dynamometers cannot meet the actual operational needs. Therefore, the design and research of multi-dimensional sensors have been developed, and some achievements have been made in sensor structure and performance.

[0003] Since the 1970s, the research on multi-dimensional force sensors has a history of more than half a century. According to the sensing principle, there are resistance strain sensors, capacitive sensors, optical sensors, etc. At present, resistance strain gauge multi-dimensional force sensors have been developed early and widely used, with the characteristics of high precision and high sensitivity.

[0004] However, traditional strain gauge sensors require more strain gauges to be attached, and have poor anti-interference capabilities, and cannot be used normally in harsh environments. With the development of fiber Bragg grating sensing technology, fiber Bragg gratings are widely used in various sensing fields. Compared with traditional sensors, fiber Bragg grating sensors have many advantages, such as anti-electromagnetic interference, strong corrosion resistance, high temperature resistance, no temperature zero drift of wavelength value, multiple gratings with different central wavelengths can be connected in series on the same optical fiber, the number of signal leads of the sensor can be greatly reduced, and it can work in complex environments.

[0005] In the document with patent application number 201911130106.2 and titled "A double-cross beam three-dimensional force sensor based on fiber grating", a double-cross multi-dimensional force sensor structure is disclosed. The setting of the double-cross beam structure makes the sensor larger in size, which is not convenient for integration in the finger position of the robot. Summary of the invention

[0006] In order to solve the problem that the existing multi-dimensional force detection sensors for robot fingers are inconvenient to use, the present invention provides a multi-dimensional force sensing device and method for robot fingers based on fiber gratings. Cantilever beams and gratings arranged thereon are arranged in the directions of the X, Y and Z axes. By applying force to the finger shell, the size and direction of the multi-dimensional force on the finger shell are calculated by utilizing the phenomenon that the central wavelength of the reflected light of the grating is changed under the force. The device has a simple structure, high sensitivity and is easy to maintain.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] A multi-dimensional force sensing device for a robot finger based on fiber gratings, comprising a finger housing, a multi-dimensional force sensor is arranged inside the finger housing, the multi-dimensional force sensor comprises a plurality of gratings and a first cantilever beam, a second cantilever beam and a third cantilever beam for deforming with an external force acting on the finger housing, the first cantilever beam and the second cantilever beam are arranged in the same plane, the third cantilever beam is perpendicular to the plane where the first cantilever beam and the second cantilever beam are located, a plurality of the gratings are arranged on the surfaces of the first cantilever beam, the second cantilever beam and the third cantilever beam, and the first cantilever beam cooperates with the grating to sense X-axis force;

[0009] The second cantilever beam cooperates with the grating to sense the force on the Y axis;

[0010] The third cantilever beam cooperates with the grating to sense the force on the Z axis;

[0011] A plurality of the gratings are connected to an optical detection system for measuring multi-dimensional forces.

[0012] Furthermore, the first cantilever beam and the second cantilever beam are rhombus-shaped plates of equal length, the central axes of the first cantilever beam and the second cantilever beam are perpendicular to each other, the first cantilever beam includes an A portion and a B portion of equal length, the second cantilever beam includes a C portion and a D portion of equal length, the A portion, the B portion, the C portion, and the D portion are provided with a connecting ring, the lower part of the inner ring surface of the connecting ring is connected to the tip position of the A portion, the B portion, the C portion, and the D portion by an arc transition, the upper end surfaces of the A portion, the B portion, the C portion, and the D portion are fixedly provided with gratings, the multiple gratings are respectively distributed along the axes of the A portion, the B portion, the C portion, and the D portion, the gratings are perpendicular to each other, and the first cantilever beam, the second cantilever beam, and the connecting ring are an integrated structure.

[0013] Furthermore, the first cantilever beam and the second cantilever beam are combined to form a cross-shaped plate body, a support tube is provided in the middle of the bottom surface of the cross-shaped plate body, the support tube is a circular tubular structure, the support tube and the first cantilever beam and the second cantilever beam are an integrated structure, the lower end surface of the support tube is fixedly connected to a base, and the base is a disc-shaped structure.

[0014] Furthermore, the third cantilever beam includes an arched portion, a connecting portion and a contact portion, the arched portion is an arched plate body made of elastic material, a connecting portion is arranged at one end of the arched portion, and a contact portion is arranged at the other end, the contact portion, the connecting portion and the arched portion are an integrated structure, a grating is arranged along the axis of the arched portion, the connecting portion is a cylindrical structure, the connecting portion and the arched portion are arranged inside the supporting tube, the bottom surface of the connecting portion is in contact with the upper end surface of the base, and the contact portion is a hemispherical structure, and the contact portion is arranged outside the supporting tube.

[0015] Further, the finger housing includes a hemispherical outer shell and a disc-shaped pressure ring arranged at the bottom of the outer shell, the outer shell and the pressure ring are an integrated structure, and the bottom surface of the pressure ring contacts the top surface of the contact portion;

[0016] A cylindrical inner groove is opened on the upper part of the inner ring surface of the connecting ring, and the pressure ring is arranged in the gap position of the inner groove. The upper end surface of the pressure ring fits with the upper end surface of the inner groove, and a gap is left between the lower end surface and the lower end surface of the inner groove. The shell is movably connected with the connecting ring.

[0017] Furthermore, the optical detection system includes a light source adjustment module, a coupler, a conversion module, a DSP unit, a main control unit and a host computer. The light source adjustment module outputs an optical signal which is transmitted to multiple gratings respectively through the coupler. The optical signals output by the multiple gratings are photoelectrically converted through the conversion module. The conversion module is connected to the DSP unit. The electrical signal output by the conversion module is processed by the DSP unit and transmitted to the main control unit. The main control unit includes an MCU chip. The main control unit is connected to the host computer through an RS232 serial port. The main control unit transmits the detection signal to the host computer through the RS232 serial port.

[0018] A method for calculating multi-dimensional force based on a multi-dimensional force sensing device for robot fingers based on fiber gratings comprises the following steps:

[0019] Step 1: The light source adjustment module outputs a light signal to the grating, and after being reflected by the grating, the reflected light is output. The central wavelength of the reflected light is λ B ;

[0020] When external stress acts on the grating, the grating is deformed, so that the central wavelength of the reflected light shifts. The central wavelength of the reflected light is related to the grating period and the effective refractive index of the grating. The grating produces an elastic light effect. At this time, the effective refractive index of the grating changes, and the central wavelength of the reflected light is linearly related to the stress on the grating. Therefore, the central wavelength of the reflected light is shifted by Δλ. B , calculate the axis strain Δε at the reference point, and have;

[0021]

[0022] Where P e is the elastic-optical coefficient;

[0023] So we have:

[0024]

[0025] Step 2: The third cantilever beam is pressed downward. The arched portion is an arched plate made of elastic material. From elastic mechanics and material mechanics, it can be known that when the external axial load is F, its strain is:

[0026]

[0027] Where: I is the section inertia moment; E is the elastic modulus; n is the number of cuts in the arch; L1 is the length of the short beam of the arch; L2 is the length of the long beam of the arch; L is the length of the arch; From equations (1.2) and (2.1), the relationship between the wavelength drift and the axial load is:

[0028]

[0029] Step 3: Affected by the Z-axis stress, the pressure ring moves downward, and the first cantilever beam and the second cantilever are subjected to force. From material mechanics, it can be known that when the external axial load is F, its strain can be expressed as:

[0030]

[0031] From equations (1.2) and (3.1), we can get the relationship between stress and wavelength:

[0032]

[0033] Where F is the force on the free end of the beam, b and h are the width and thickness of the beam, E is the Young's modulus of the beam, and l is the length of the beam;

[0034] Step 4: After respectively calculating the stresses of the first cantilever beam, the second cantilever beam and the third cantilever beam, the horizontal stress of the robot finger shell is calculated;

[0035] Assume that the finger housing is subjected to a horizontal force F (force on the Z axis), and its components on the X axis and Y axis are FX (force on the X axis) and FY (force on the Y axis) respectively;

[0036] At the same time, let the angle between F and the X-axis be θ, then the relationship between F and FX, FY is:

[0037]

[0038] Then find out the magnitude and direction of the force acting on the finger.

[0039] Through the above technical solution, the beneficial effects of the present invention are:

[0040] 1. The present invention is provided with a first cantilever beam, a second cantilever beam and a third cantilever beam that are deformed with the external force of the finger shell, the first cantilever beam and the second cantilever beam are arranged in the same plane, the third cantilever beam is perpendicular to the plane where the first cantilever beam and the second cantilever beam are located, and a plurality of gratings are arranged on the surfaces of the first cantilever beam, the second cantilever beam and the third cantilever beam, the first cantilever beam cooperates with the grating to sense the force on the X axis; the second cantilever beam cooperates with the grating to sense the force on the Y axis; the third cantilever beam cooperates with the grating to sense the force on the Z axis; and a plurality of the gratings are connected to an optical detection system for measuring multi-dimensional forces.

[0041] When the robot finger shell is subjected to external force, the force component acting on the Z axis will cause the finger shell to slide downward, causing the third cantilever beam to deform. By using the phenomenon that the center wavelength of the reflected light changes when the grating is subjected to force, the center wavelength of the reflected light changes when the grating set on the surface of the third cantilever beam is subjected to stress, and finally the wavelength information is demodulated by the optical detection system. At the same time, the force component acting on the X and Y axes will cause the first cantilever beam and the second cantilever beam to deform. Similarly, the center wavelength generated by the grating on the first cantilever beam and the second cantilever beam will also shift. Through processing and calculation, the magnitude and direction of the force are determined, and the multi-dimensional force sensor is integrated into the robot finger to achieve the effect of accurately and effectively completing multi-dimensional force detection.

[0042] 2. The present invention adopts grating as the transmission medium and transmits information with optical signals, which is not affected by electromagnetic interference. The grating is small in size, light in structure, simple in measurement principle, good in stability, strong in anti-interference ability, and long in service life. It can work in harsh environments such as acid, alkali, and salt. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The present invention is one of the structural schematic diagrams of a multi-dimensional force sensing device and method for robot fingers based on fiber grating.

[0044] Figure 2 The present invention is one of the structural schematic diagrams of a multi-dimensional force sensing device and method for robot fingers based on fiber grating.

[0045] Figure 3 The present invention is the third structural schematic diagram of a multi-dimensional force sensing device and method for robot fingers based on fiber grating.

[0046] Figure 4 The present invention is the fourth structural schematic diagram of a multi-dimensional force sensing device and method for robot fingers based on fiber grating.

[0047] Figure 5 The present invention is the fifth structural schematic diagram of a multi-dimensional force sensing device and method for robot fingers based on fiber grating.

[0048] Figure 6 The present invention is a force analysis diagram of the third cantilever beam of a multi-dimensional force sensing device and method for robot fingers based on fiber grating.

[0049] Figure 7 The present invention is a force analysis diagram of a first cantilever beam or a second cantilever beam of a multi-dimensional force sensing device and method for a robot finger based on fiber grating.

[0050] Figure 8 The present invention is an electrical schematic diagram of an optical detection system of a multi-dimensional force sensing device and method for robot fingers based on fiber grating.

[0051] The numbers in the accompanying drawings are: 1 is the first cantilever beam, 2 is the second cantilever beam, 3 is the third cantilever beam, 4 is the grating, 5 is the connecting ring, 6 is the finger shell, 7 is the base, 8 is the supporting tube, 9 is the light source adjustment module, 10 is the conversion module, 11 is the main control unit, 12 is the upper computer, 301 is the bow portion, 302 is the connecting portion, 303 is the contact portion, 601 is the outer shell, and 602 is the pressure ring. DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0053] Embodiment 1: as Figures 1 to 8 As shown, a multi-dimensional force sensing device for robot fingers based on fiber gratings includes a finger housing 6, a multi-dimensional force sensor is arranged inside the finger housing 6, the multi-dimensional force sensor includes a plurality of gratings 4 and a first cantilever beam 1, a second cantilever beam 2 and a third cantilever beam 3 for deforming with the external force of the finger housing 6, the first cantilever beam 1 and the second cantilever beam 2 are arranged in the same plane, the third cantilever beam 3 is perpendicular to the plane where the first cantilever beam 1 and the second cantilever beam 2 are located, a plurality of the gratings 4 are arranged on the surfaces of the first cantilever beam 1, the second cantilever beam 2 and the third cantilever beam 3, and the first cantilever beam 1 cooperates with the grating 4 to sense the force on the X-axis;

[0054] The second cantilever beam 2 cooperates with the grating 4 to sense the Y-axis force;

[0055] The third cantilever beam 3 cooperates with the grating 4 to sense the force on the Z axis;

[0056] The plurality of gratings 4 are connected to an optical detection system for measuring multi-dimensional forces.

[0057] In order to improve the sensitivity of the grating 4, the grating 4 is arranged along the center of the connecting ring 5, such as Figure 3 As shown, the first cantilever beam 1 and the second cantilever beam 2 are rhombus-shaped plates of equal length, the central axes of the first cantilever beam 1 and the second cantilever beam 2 are perpendicular to each other, the first cantilever beam 1 includes an A portion and a B portion of equal length, the second cantilever beam 2 includes a C portion and a D portion of equal length, the A portion, the B portion, the C portion, and the D portion are provided with a connecting ring 5, the lower part of the inner ring surface of the connecting ring 5 is connected with the tip position of the A portion, the B portion, the C portion, and the D portion by an arc transition, the upper end surfaces of the A portion, the B portion, the C portion, and the D portion are fixedly provided with a grating 4, a plurality of the gratings 4 are respectively distributed along the axes of the A portion, the B portion, the C portion, and the D portion, the gratings 4 are perpendicular to each other, and the first cantilever beam 1, the second cantilever beam 2 and the connecting ring 5 are an integrated structure.

[0058] To further optimize the product structure, the first cantilever beam 1 and the second cantilever beam 2 are combined to form a cross-shaped plate body, and a support tube 8 is provided in the middle of the bottom surface of the cross-shaped plate body. The support tube 8 is a circular tubular structure, and the support tube 8 and the first cantilever beam 1 and the second cantilever beam 2 are an integrated structure. The lower end surface of the support tube 8 is fixedly connected to a base 7, and the base 7 is a disc-shaped structure.

[0059] In order to make the arched portion 301 deform under stress, the third cantilever beam 3 includes an arched portion 301, a connecting portion 302 and a contact portion 303. The arched portion 301 is an arched plate made of elastic material. The connecting portion 302 is arranged at one end of the arched portion 301, and the contact portion 303 is arranged at the other end. The contact portion 303, the connecting portion 302 and the arched portion 301 are an integrated structure. A grating 4 is arranged along the axis of the arched portion 301. The connecting portion 302 is a cylindrical structure. The connecting portion 302 and the arched portion 301 are arranged inside the support tube 8, and the bottom surface of the connecting portion 302 contacts the upper end surface of the base 7. The contact portion 303 is a hemispherical structure, and the contact portion 303 is arranged outside the support tube 8.

[0060] In order to reflect that the finger housing 6 is linked with the X-axis and Y-axis forces after being stressed, the finger housing 6 includes a hemispherical shell 601 and a disc-shaped pressure ring 602 arranged at the bottom of the shell 601. The shell 601 and the pressure ring 602 are an integrated structure, and the bottom surface of the pressure ring 602 contacts the top surface of the contact portion 303;

[0061] A cylindrical inner groove is opened on the upper part of the inner ring surface of the connecting ring 5, and the pressing ring 602 is arranged in the gap position of the inner groove. The upper end face of the pressing ring 602 is in contact with the upper end face of the inner groove, and a gap is left between the lower end face and the lower end face of the inner groove. The shell 6 is movably connected to the connecting ring 5.

[0062] To facilitate the analysis of the optical signal of the grating 4, the optical detection system includes a light source adjustment module 9, a coupler, a conversion module 10, a DSP unit, a main control unit 11 and a host computer 12. The light source adjustment module 9 outputs an optical signal which is transmitted to multiple gratings 4 respectively through the coupler. The optical signals output by multiple gratings 4 are photoelectrically converted through the conversion module 10. The conversion module 10 is connected to the DSP unit. The conversion module 10 outputs an electrical signal which is processed by the DSP unit and transmitted to the main control unit 11. The main control unit 11 includes an MCU chip. The main control unit 11 is connected to the host computer 12 via an RS232 serial port. The main control unit 11 transmits the detection signal to the host computer 12 via the RS232 serial port.

[0063] In this embodiment, if Figure 3 and Figure 6 and Figure 8As shown, the light source adjustment module 9 is used to emit a light source, the coupler is a 3dB coupler, the grating 4 is specifically a fiber Bragg grating, the number of the grating 4 is 5, which are respectively arranged on the A part and the B part of the first cantilever beam 1, the C part and the D part of the second cantilever beam 2 and the third cantilever beam, and the five gratings 4 are connected in series, and the numbers in the figure correspond to FBG1, FBG3 and FBG2, FBG4 and FBG5 respectively, the conversion module 10 includes a photoelectric converter, an operational amplifier, an IV converter, and an A / D converter. The conversion module 10 converts the reflected light signal of the grating 4 into a digital signal carrying wavelength information, and the MUC chip is specifically a single-chip microcomputer;

[0064] The light source adjustment module 9 is connected to the MUC chip through the UART serial port. The MUC chip controls the output of the light source adjustment module 9. The adjustment module 9 outputs an optical signal to the grating 4 through a 3dB coupler. The grating 4 outputs reflected light to the conversion module 10. The conversion module 10 sends the digital signal carrying wavelength information to the single-chip microcomputer after being processed by the DSP unit. The DSP unit communicates with the MUC chip through the ADC serial port. Through the synchronization signal of the light source adjustment module 9 and the reflected light signal processed by the DSP unit, the MUC chip obtains the reflection center wavelength of the grating 4 through relevant calculations and transmits the data to the host computer 12.

[0065] Example 2: Figures 3 to 7 As shown, a method for calculating multi-dimensional force based on a multi-dimensional force sensing device of a robot finger based on fiber grating includes the following steps:

[0066] First, when no force is applied to the outside of the finger housing 6, the contact portion 303 contacts the bottom surface of the pressure ring 602, and the upward supporting force of the contact portion 303 and the gravity of the housing 6 are in a force balance state. At this time, the upper end surface of the pressure ring 602 fits with the upper end surface of the groove in the connecting ring 5;

[0067] Step 1: The light source adjustment module 9 outputs a light signal to the grating 4, and outputs a reflected light after being reflected by the grating 4. The central wavelength of the reflected light is λ B ;

[0068] When external stress acts on grating 4, grating 4 is deformed, so that the central wavelength of the reflected light is shifted. The central wavelength of the reflected light is related to the period of grating 4 and the effective refractive index of grating 4. Grating 4 produces an elastic light effect. At this time, the effective refractive index of grating 4 changes, and the central wavelength of the reflected light is linearly related to the stress on grating 4. Therefore, the central wavelength of the reflected light is shifted by Δλ. B , calculate the axis strain Δε at the reference point, and have;

[0069]

[0070] Where Pe is the elastic-optical coefficient;

[0071] So we have:

[0072]

[0073] Then, when stress exists outside the finger housing 6, the pressure ring 602 moves downward with the housing 601 under force, and the contact portion 303 is stressed, causing the arched portion 301 to deform under force;

[0074] Step 2: The third cantilever beam 3 is pressed downward. The arched portion 301 is an arched sheet made of stainless steel. It can be known from elastic mechanics and material mechanics that when the external axial load is F, its strain is:

[0075]

[0076] Among them: Figure 6 As shown, I is the section inertia moment; E is the elastic modulus; n is the number of cuts in the arch 301; L1 is the short beam length of the arch 301; L2 is the long beam length of the arch 303; L is the length of the arch 301; From equations (1.2) and (2.1), the relationship between the wavelength drift and the axial load is:

[0077]

[0078] Furthermore, when the finger housing 6 is subjected to any external force, the longitudinal force component causes the finger housing 6 to move downward and the arched portion 301 to deform, while the transverse force component causes the first cantilever beam 1 and the second cantilever beam 2 on the connecting ring 5 to be strained.

[0079] Step 3: Affected by the Z-axis stress, the pressure ring 601 moves downward, and the first cantilever beam 1 and the second cantilever 2 are subjected to force. From material mechanics, it can be known that when the external axial load is F, the strain can be expressed as:

[0080]

[0081] From equations (1.2) and (3.1), we can get the relationship between stress and wavelength:

[0082]

[0083] Here, taking the B portion of the first cantilever beam 1 as an example, Figure 7 As shown, F is the force on the free end of the beam, b and h are the width and thickness of the beam, E is the Young's modulus of the beam, and l is the length of the beam;

[0084] Step 4: After respectively calculating the stresses of the first cantilever beam 1, the second cantilever beam 2 and the third cantilever beam 3, the horizontal force of the robot finger housing 6 is calculated;

[0085] Assume that the finger housing 6 is subjected to a horizontal force F (force on the Z axis), and the components of the forces on the X axis and Y axis are FX (force on the X axis) and FY (force on the Y axis) respectively;

[0086] At the same time, let the angle between F and the X-axis be θ, then the relationship between F and FX, FY is:

[0087]

[0088] Then find out the magnitude and direction of the force acting on the finger.

[0089] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made according to the structures, features and principles described in the patent scope of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A method for calculating multi-dimensional force of a robot finger multi-dimensional force sensing device based on fiber grating, characterized in that: A robot finger multi-dimensional force sensing device based on fiber grating comprises a finger housing (6), wherein a multi-dimensional force sensor is arranged inside the finger housing (6), wherein the multi-dimensional force sensor comprises a plurality of gratings (4) and a first cantilever beam (1), a second cantilever beam (2) and a third cantilever beam (3) for generating deformation in response to an external force acting on the finger housing (6), wherein the first cantilever beam (1) and the second cantilever beam (2) are arranged in the same plane, and the third cantilever beam (3) is perpendicular to the plane where the first cantilever beam (1) and the second cantilever beam (2) are located, wherein the plurality of gratings (4) are arranged on the surfaces of the first cantilever beam (1), the second cantilever beam (2) and the third cantilever beam (3), and the first cantilever beam (1) cooperates with the gratings (4) to sense X-axis force; The second cantilever beam (2) cooperates with the grating (4) to sense the Y-axis force; The third cantilever beam (3) cooperates with the grating (4) to sense the force on the Z axis; A plurality of the gratings (4) are connected to an optical detection system for measuring multi-dimensional forces; The first cantilever beam (1) and the second cantilever beam (2) are rhombus-shaped plates of equal length. The central axes of the first cantilever beam (1) and the second cantilever beam (2) are perpendicular to each other. The first cantilever beam (1) comprises an A portion and a B portion of equal length. The second cantilever beam (2) comprises a C portion and a D portion of equal length. The A portion, the B portion, the C portion and the D portion are provided with a connecting ring (5). The lower part of the inner ring surface of the connecting ring (5) is connected to the tip of the A portion, the B portion, the C portion and the D portion by an arc transition. The upper end surfaces of the A portion, the B portion, the C portion and the D portion are fixedly provided with gratings (4). A plurality of the gratings (4) are respectively distributed along the axes of the A portion, the B portion, the C portion and the D portion. The gratings (4) are perpendicular to each other. The first cantilever beam (1), the second cantilever beam (2) and the connecting ring (5) are an integrated structure. The first cantilever beam (1) and the second cantilever beam (2) are combined to form a cross-shaped plate body, a support tube (8) is provided in the middle of the bottom surface of the cross-shaped plate body, the support tube (8) is a circular tube structure, the support tube (8) and the first cantilever beam (1) and the second cantilever beam (2) are an integrated structure, the lower end surface of the support tube (8) is fixedly connected to a base (7), and the base (7) is a disc-shaped structure; The third cantilever beam (3) comprises an arched portion (301), a connecting portion (302) and a contact portion (303); the arched portion (301) is an arched plate made of elastic material; the connecting portion (302) is arranged at one end of the arched portion (301) and the contact portion (303) is arranged at the other end; the contact portion (303), the connecting portion (302) and the arched portion (301) are an integrated structure; a grating (4) is arranged along the axis of the arched portion (301); the connecting portion (302) is a cylindrical structure; the connecting portion (302) is arranged inside the support tube (8) and is fixedly connected to the support tube (8) by means of threads; and the contact portion (303) is a hemispherical structure; The finger housing (6) comprises a hemispherical outer shell (601) with a hollow interior and a circular annular pressure ring (602) arranged at the bottom of the outer shell (601); the outer shell (601) and the pressure ring (602) are an integrated structure, and the top of the inner side surface of the outer shell (601) is in contact with the contact portion (303); The upper portion of the inner ring surface of the connecting ring (5) is provided with a cylindrical inner groove, the pressing ring (602) is arranged at a gap position of the inner groove, the upper end surface of the pressing ring (602) is in contact with the upper end surface of the inner groove, and a gap is left between the lower end surface and the lower end surface of the inner groove, and the housing (6) is movably connected to the connecting ring (5); The optical detection system comprises a light source adjustment module (9), a coupler, a conversion module (10), a DSP unit, a main control unit (11) and a host computer (12); the light source adjustment module (9) outputs an optical signal which is transmitted to a plurality of gratings (4) via the coupler; the optical signals output by the plurality of gratings (4) are subjected to photoelectric conversion via the conversion module (10); the conversion module (10) is connected to the DSP unit; the electrical signal output by the conversion module (10) is processed by the DSP unit and transmitted to the main control unit (11); the main control unit (11) comprises an MCU chip; the main control unit (11) is connected to the host computer (12) via an RS232 serial port; and the main control unit (11) transmits a detection signal to the host computer (12) via the RS232 serial port; A method for calculating multi-dimensional forces comprises the following steps: Step 1: The light source adjustment module (9) outputs a light signal to the grating (4), and after being reflected by the grating (4), a reflected light is output, wherein the central wavelength of the reflected light is λ B ; When external stress acts on the grating (4), the grating (4) is deformed, so that the central wavelength of the reflected light is shifted, wherein the central wavelength of the reflected light is related to the period of the grating (4) and the effective refractive index of the grating (4), and the grating (4) produces an elastic light effect. At this time, the effective refractive index of the grating (4) changes, and the central wavelength of the reflected light is linearly related to the stress on the grating (4). Therefore, the central wavelength of the reflected light is shifted by Δλ B , calculate the axis strain Δε at the reference point, we have; Among them e is the elastic-optical coefficient; So we have: Step 2: The third cantilever beam (3) is pressed downward by force. The arched portion (301) is an arched plate made of elastic material. It can be known from elastic mechanics and material mechanics that when the external axial load is F, its strain is: Where: I is the section inertia moment; E is the elastic modulus; n is the number of cuts in the arched portion (301); L1 is the length of the short beam of the arched portion (301); L2 is the length of the long beam of the arched portion (301); L is the length of the arched portion (301); From equations (1.2) and (2.1), the relationship between the wavelength drift and the axial load can be obtained as follows: Step 3: Affected by the Z-axis stress, the pressure ring (602) moves downward, and the first cantilever beam (1) and the second cantilever (2) are subjected to force. From material mechanics, it can be known that when the external axial load is F, the strain can be expressed as: From equations (1.2) and (3.1), we can get the relationship between stress and wavelength: Where F is the force on the free end of the beam, b and h are the width and thickness of the beam, E is the Young's modulus of the beam, and l is the length of the beam; Step 4: After respectively calculating the stresses of the first cantilever beam (1), the second cantilever beam (2) and the third cantilever beam (3), the horizontal stress of the robot finger housing (6) is further calculated; Assume that the finger housing (6) is subjected to a horizontal force F (force on the Z axis), and the components of the forces on the X axis and Y axis are FX (force on the X axis) and FY (force on the Y axis) respectively; At the same time, let the angle between F and the X-axis be θ, then the relationship between F and FX, FY is: Then find out the magnitude and direction of the force acting on the finger.

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