Six-dimensional force sensor and its elastomer

Abstract

The application relates to the technical field of sensors and discloses a six-dimensional force sensor and an elastic body thereof, which comprises a center platform, an inner ring, an outer ring, a first group of elastic beams and a second group of elastic beams. The inner ring surrounds the center platform; the outer ring surrounds the inner ring; the center platform, the inner ring and the outer ring are concentrically arranged; the first group of elastic beams is connected to the inner edge of the inner ring and the center platform; the second group of elastic beams is connected to the inner edge of the outer ring and the outer edge of the inner ring; the torsional stiffness of the first group of elastic beams is greater than that of the second group of elastic beams; when the center platform is subjected to force, the first group of elastic beams is adapted to be subjected to shearing and / or tensile and compressive deformation under the action of the force load, and the center platform translates relative to the inner ring; the second group of elastic beams is adapted to be subjected to bending and / or torsional deformation under the action of the moment load, and the inner ring rotates relative to the outer ring. The structure of the elastic body reduces the physical overlap of the sensing areas of the force load and the moment load, realizes the identification of the force load and the moment load respectively, improves the sensitivity of each axis, and reduces the measurement error.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and specifically to a six-dimensional force sensor and its elastomer. Background Technology

[0002] A six-dimensional force sensor is a high-end force sensor capable of simultaneously measuring forces (Fx, Fy, Fz) and moments (Mx, My, Mz) in three spatial directions. Its core is based on the strain effect, utilizing the change in resistance of a strain gauge caused by the deformation of an elastic body. Through signal processing and algorithm decoupling, accurate measurement of multi-dimensional forces is achieved. Six-dimensional force sensors are key components for providing force perception to machinery and equipment, and are widely used in robotics (such as precision assembly and force-controlled grinding), aerospace (such as wind tunnel testing and aircraft control), medical surgical robots, and industrial automation.

[0003] The core technology in developing six-dimensional force sensors lies in the structural design of the sensor's elastic body, as its structural form directly affects the sensor's performance. Six-dimensional force sensors require high sensitivity in each axis, low cross-interference, and a certain operating bandwidth to meet the needs of dynamic force measurement. In related technologies, such as the all-planar octagonal six-dimensional force sensor for robot joints described in publication CN121804736A, a single-layer octagonal beam structure between the fixed stage and the central loading stage is used. Force sensing is achieved through the same-layer combination of radial and circumferential beams, and inter-dimensional coupling is eliminated by the voltage cancellation of the bridge arms of the bridge circuit. However, all elastic beams are directly connected to the fixed stage and the central loading stage, resulting in physical overlap of the sensing areas for force and torque components. The sensitivity in each axis is limited by the structure and cannot be further improved, making it difficult to meet the growing demand for high-sensitivity six-dimensional force sensors in each axis in the robotics and automation fields. Summary of the Invention

[0004] This invention provides a six-dimensional force sensor and its elastomer. The structure of the elastomer enables independent sensitivity and hard decoupling of force load and torque load, reduces the physical overlap of the sensing areas of force load and torque load, realizes the separate identification of force load and torque load, improves the sensitivity of each axis, and reduces measurement error, so as to meet the growing demand of the robotics and automation fields for six-dimensional force sensors with high sensitivity in each axis.

[0005] In a first aspect, the present invention provides an elastic body for a six-dimensional force sensor, comprising: Central station; Inner ring, surrounding the central platform; An outer ring surrounds the inner ring, and the central platform, inner ring, and outer ring are arranged concentrically. The first set of elastic beams connects the inner edge of the inner ring and the central platform; The second set of elastic beams connects the inner edge of the outer ring and the outer edge of the inner ring. The torsional stiffness of the first set of elastic beams is greater than that of the second set of elastic beams. When the central platform is subjected to force, the first set of elastic beams is adapted to undergo shear and / or tensile and compressive deformation under the action of force load, and the central platform translates relative to the inner ring; the second set of elastic beams is adapted to undergo bending and / or torsional deformation under the action of moment load, and the inner ring rotates relative to the outer ring.

[0006] Beneficial effects: The central platform, inner ring and outer ring are arranged concentrically to form a three-level concentric nested structure. The inner ring, as an independent intermediate inertial body, decomposes the stress transmission path into a two-level series elastic path. The first level path consists of the central platform, the first set of elastic beams and the inner ring, and the second level path consists of the inner ring, the second set of elastic beams and the outer ring. When the central platform is subjected to force, the force load is first transmitted to the first-level path. The first set of elastic beams is adapted to undergo shear and / or tensile and compressive deformation under the force load. The central platform translates relative to the inner ring, while simultaneously reducing the tendency of the force load to be transmitted to the second-level path and reducing the sensitivity of the second set of elastic beams to the force load. Since the torsional stiffness of the first set of elastic beams is greater than that of the second set of elastic beams, the moment load will first cause the second set of elastic beams to deform. The central platform, the first set of elastic beams, and the inner ring rotate relative to the outer ring as a whole. Therefore, the second set of elastic beams is adapted to undergo bending and / or torsional deformation under the action of the moment load. The inner ring rotates relative to the outer ring, while simultaneously reducing the tendency of the moment load to be transmitted to the first-level path and reducing the sensitivity of the first set of elastic beams to the moment load. This achieves physical separation of the sensitivity characteristics of the first and second sets of elastic beams to force and moment loads, fundamentally reducing cross-coupling.

[0007] Therefore, by using the structure of the elastic body to achieve independent sensitivity and hard decoupling of force load and torque load, the physical overlap of the sensing areas of force load and torque load is reduced, enabling separate identification of force load and torque load, improving the sensitivity of each axis, and reducing measurement error, so as to meet the growing demand of the robotics and automation field for six-dimensional force sensors with high sensitivity in each axis.

[0008] In one alternative embodiment, the torsional stiffness ratio of the second set of elastic beams to the first set of elastic beams ranges from 1:4 to 1:6.

[0009] In one optional embodiment, the first group of elastic beams includes a plurality of first elastic beams arranged at a uniform angle along the circumference, and the second group of elastic beams includes a plurality of second elastic beams arranged at a uniform angle along the circumference, wherein the number of first elastic beams and second elastic beams is the same.

[0010] In one alternative embodiment, multiple first elastic beams and multiple second elastic beams are arranged in an alternating manner along the circumferential direction, and the angle between two adjacent first elastic beams and second elastic beams is 360° / (2n), where n is the number of first elastic beams or second elastic beams.

[0011] In one alternative embodiment, along the length of the first elastic beam, the first elastic beam has a first end, a middle section, and a second end, the thickness and width of the first end and the second end being greater than the thickness and width of the middle section.

[0012] In one alternative embodiment, along the thickness direction of the first elastic beam, the first elastic beam has two parallel first surfaces for mounting strain gauges. Along the thickness direction of the second elastic beam, the second elastic beam has two parallel second surfaces for mounting strain gauges, and the second surfaces are perpendicular to the plane containing the first surface.

[0013] In one optional embodiment, the inner edge of the outer ring is provided with at least two first limiting portions, and the outer edge of the inner ring is provided with at least two second limiting portions. The number of second limiting portions and first limiting portions is the same, and the second limiting portions and first limiting portions are arranged in a one-to-one correspondence. There is a gap between the first limiting portions and the second limiting portions. When the second set of elastic beams undergoes bending and / or torsional deformation at a predetermined angle, the first limiting portions and the second limiting portions abut against each other.

[0014] In one optional embodiment, the central platform is provided with a first positioning hole for connecting an external movable structure, and the outer ring is provided with a second positioning hole for connecting an external fixed structure.

[0015] Secondly, the present invention provides a six-dimensional force sensor, including the above-mentioned elastic body, and also including a strain gauge group, wherein the strain gauge group includes multiple strain gauges, and the multiple strain gauges are respectively mounted on the first group of elastic beams and the second group of elastic beams.

[0016] In one optional implementation, the strain gauges on the first set of elastic beams form three full-bridge circuits to measure Fx, Fy and Fz respectively, and the strain gauges on the second set of elastic beams form three full-bridge circuits to measure Mx, My and Mz respectively. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the elastomer according to an embodiment of the present invention; Figure 2 for Figure 1 A top view of an elastic body; Figure 3 for Figure 1 Schematic diagram of the cross-sectional structure of a medium elastic body; Figure 4 for Figure 1 Another cross-sectional structural diagram of the medium elastomer; Figure 5 This is a schematic diagram of the installation structure of the elastomer and strain gauge according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the strain of the elastomer under Fx load according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the strain of the elastomer under the Fz load according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the strain of the elastomer under Mx load according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the strain of the elastomer under Mz load according to an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Center platform; 11. First positioning hole; 12. Mounting hole; 2. Inner ring; 3. Outer ring; 31. Second positioning hole; 4. First set of elastic beams; 41. First elastic beam; 411. First end; 412. Middle section; 4121. First surface; 413. Second end; 5. Second set of elastic beams; 51. Second elastic beam; 511. Second surface; 61. First limiting part; 62. Second limiting part. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The following is combined Figures 1 to 9 The following describes embodiments of the present invention.

[0022] like Figure 1 and Figure 2 As shown, according to an embodiment of the present invention, in one aspect, an elastic body for a six-dimensional force sensor is provided, comprising: Central Station 1; Inner ring 2 surrounds central platform 1; Outer ring 3 surrounds inner ring 2, and central platform 1, inner ring 2 and outer ring 3 are arranged concentrically; The first set of elastic beams 4 connects the inner edge of the inner ring 2 and the central platform 1; The second set of elastic beams 5 connects the inner edge of the outer ring 3 and the outer edge of the inner ring 2. The torsional stiffness of the first set of elastic beams 4 is greater than that of the second set of elastic beams 5. When the central platform 1 is subjected to force, the first set of elastic beams 4 is adapted to undergo shear and / or tensile and compressive deformation under the action of force load, and the central platform 1 translates relative to the inner ring 2; the second set of elastic beams 5 is adapted to undergo bending and / or torsional deformation under the action of moment load, and the inner ring 2 rotates relative to the outer ring 3.

[0023] Specifically, the central platform 1 is a platform structure located at the very center of the elastic body. It is the input end of the six-dimensional force sensor for measuring loads and is used to connect with the external active structure being measured to receive externally applied force loads and torque loads. Force loads refer to the force components acting in the three spatial coordinate axes, including the force along the X-axis, the force along the Y-axis, and the force along the Z-axis. Torque loads refer to the torque components acting around the three spatial coordinate axes, including the torque around the X-axis, the torque around the Y-axis, and the torque around the Z-axis.

[0024] The central platform 1, inner ring 2, and outer ring 3 are concentrically arranged, forming a three-level concentric nested structure. Concentric arrangement means that in the unloaded natural state of the central platform 1, the center points of the three coincide. There is a gap between the inner ring 2 and the central platform 1, and a gap between the outer ring 3 and the inner ring 2. The outer ring 3 supports the inner ring 2 through a second set of elastic beams 5, and the inner ring 2 supports the central platform 1 through a first set of elastic beams 4. The inner ring 2 acts as an independent intermediate inertial body, decomposing the stress transmission path into a two-level series elastic path. The first-level path consists of the central platform 1, the first set of elastic beams 4, and the inner ring 2; the second-level path consists of the inner ring 2, the second set of elastic beams 5, and the outer ring 3. Under force loads along the X-axis or Y-axis, the first elastic beam 41 can undergo tensile and compressive deformation; under force loads along the Z-axis, the first elastic beam 41 can undergo shear deformation. Under moment loads around the X-axis or Y-axis, the second elastic beam 51 can undergo torsional deformation; under moment loads around the Z-axis, the second elastic beam 51 can undergo bending deformation.

[0025] When the central platform 1 is subjected to force, the force load is first transmitted to the first-level path. The first set of elastic beams 4 is adapted to undergo shear and / or tensile and compressive deformation under the action of the force load. The central platform 1 translates relative to the inner ring 2, while reducing the tendency of the force load to be transmitted to the second-level path and reducing the sensitivity of the second set of elastic beams 5 to the force load. Since the torsional stiffness of the first set of elastic beams 4 is greater than that of the second set of elastic beams 5, the moment load will first cause the second set of elastic beams 5 to deform. The central platform 1, the first set of elastic beams 4 and the inner ring 2 rotate relative to the outer ring 3 as a whole. Therefore, the second set of elastic beams 5 is adapted to undergo bending and / or torsional deformation under the action of the moment load. The inner ring 2 rotates relative to the outer ring 3, while reducing the tendency of the moment load to be transmitted to the first-level path and reducing the sensitivity of the first set of elastic beams 4 to the moment load. Compared to the traditional single-stage elastic beam, the two-stage series elastic path has a first set of elastic beams 4 that mainly bears the deformation caused by force loads, and a second set of elastic beams 5 that mainly bears the deformation caused by moment loads. This achieves physical separation of the sensitivity characteristics of the first set of elastic beams 4 and the second set of elastic beams to force loads and moment loads, fundamentally reducing cross-coupling.

[0026] Therefore, by using the structure of the elastic body to achieve independent sensitivity and hard decoupling of force load and torque load, the physical overlap of the sensing areas of force load and torque load is reduced, enabling separate identification of force load and torque load, improving the sensitivity of each axis, and reducing measurement error, so as to meet the growing demand of the robotics and automation field for six-dimensional force sensors with high sensitivity in each axis.

[0027] In this embodiment, the torsional stiffness ratio of the second set of elastic beams 5 and the first set of elastic beams 4 is in the range of 1:4 to 1:6. This range of torsional stiffness ratios ensures that the second set of elastic beams 5 is more sensitive to moment loads than the first set of elastic beams 4.

[0028] Specifically, the torsional stiffness of the first set of elastic beams 4 is defined as k. t1 The torsional stiffness of the second set of elastic beams 5 is defined as k. t2 k t2 :k t1 =1:4-1:6, including the two boundary ratios of 1:4 and 1:6. Within this range of torsional stiffness ratios, when a moment load is applied to the central platform 1, since the torsional stiffness of the first set of elastic beams 4 is four to six times that of the second set of elastic beams 5, the second set of elastic beams 5 is more likely to deform under the action of moment load. This realizes that the moment load is mainly borne by the second set of elastic beams 5 through bending and torsional deformation, while reducing the degree of deformation of the first set of elastic beams 4 under the action of moment load, so that the second set of elastic beams 5 is dedicated to moment sensing.

[0029] Furthermore, if the torsional stiffness ratio k t2 :k t1 >1:4, meaning the strain induced by the second group of elastic beams 5 under moment load is too small, resulting in insufficient signal-to-noise ratio and decreased resolution; simultaneously, the moment signal will be intruded into the force channel, reducing the decoupling effect; if the torsional stiffness ratio k t2 :k t1 The ratio is less than 1:6, meaning the strain caused by the second set of elastic beams 5 under moment load is too large, which will cause frequent overload limit occurrences. At the same time, the natural frequency of the second set of elastic beams 5 decreases and overlaps with the frequency of dynamic load. Therefore, the torsional stiffness ratio of the two is set to 1:4-1:6. This range ensures that the second set of elastic beams 5 has sufficient measurement sensitivity and signal-to-noise ratio for moment load, while avoiding the problems of excessive deformation, frequent overload, and decreased natural frequency caused by insufficient stiffness. At the same time, it effectively suppresses crosstalk between moment-to-force channel and force-to-moment channel. Within this stiffness ratio range, the decoupling effect of the two sets of elastic beams is better, achieving comprehensive optimization of decoupling degree, sensitivity, range, and dynamic bandwidth.

[0030] It should be noted that the method for adjusting the first group of elastic beams 4 and the second group of elastic beams 5 can be through thickness differentiation, that is, the thickness of the second group of beams can be reduced to 0.55 to 0.7 times the thickness of the first group of beams. (See [reference needed]). Figure 2 and Figure 4 Let the thickness of the first set of elastic beams 4 be defined as h1, and the thickness of the second set of elastic beams 5 be defined as h2. The cubic dependence of the torsional stiffness of the elastic beams on the thickness is k. t By adjusting h1 and h2 using the cubic dependence ∝h³, a torsional stiffness ratio of 1:4 to 1:6 can be achieved with relatively small dimensional differences. Alternatively, as an optional adjustment method, appropriately increasing the length of the second set of elastic beams 5 or narrowing the width of the second set of elastic beams 5 can also adjust the torsional stiffness ratio.

[0031] In this embodiment, the first group of elastic beams 4 includes multiple first elastic beams 41, which are arranged at a uniform angle along the circumference. The second group of elastic beams 5 includes multiple second elastic beams 51, which are arranged at a uniform angle along the circumference. The number of first elastic beams 41 and second elastic beams 51 is the same.

[0032] Specifically, each first elastic beam 41 independently connects the central platform 1 and the inner ring 2, jointly undertaking the elastic support function of the central platform 1. Each second elastic beam 51 independently connects the inner ring 2 and the outer ring 3, jointly undertaking the elastic suspension function of the inner ring 2. The uniform angular arrangement along the circumference means that the elastic beams in the same group are distributed at equal angular intervals around the central axis, and the central angle between any two adjacent elastic beams in the same group is equal, ensuring the symmetry and uniform force distribution of the elastic structure. The number of first elastic beams 41 and the number of second elastic beams 51 are defined as n, where n is a positive integer. The angle between two adjacent first elastic beams 41 is 360° / n, and the angle between two adjacent second elastic beams 51 is 360° / n.

[0033] For example, the envelope size of the elastomer can be φ35mm×4mm, where the outer diameter of the outer ring 3 corresponds to the outer diameter of the elastomer, the outer diameter of the inner ring 2 is 24mm, and the wall thickness of the inner ring 2 is 1.5mm. The first set of elastic beams 4 includes four first elastic beams 41, with an angle of 90° between adjacent first elastic beams 41. The second set of elastic beams 5 includes four second elastic beams 51, with an angle of 90° between adjacent second elastic beams 51. The four first elastic beams 41 can sense Fx, Fy, and Fz respectively through a full-bridge circuit combination, and the four second elastic beams 51 can sense Mx, My, and Mz respectively through a full-bridge circuit combination, achieving two-stage stiffness decoupling in a small size. Of course, by increasing the outer diameter of the outer ring 3 and the outer diameter of the inner ring 2, the distance between the inner ring 2 and the outer ring 3 increases, allowing for more first elastic beams 41 and second elastic beams 51 to be accommodated, such as 6 or 8 beams.

[0034] like Figure 2 As shown, in this embodiment, multiple first elastic beams 41 and multiple second elastic beams 51 are arranged in an alternating pattern along the circumferential direction. The angle between two adjacent first elastic beams 41 and second elastic beams 51 is 360° / (2n), where n is the number of first elastic beams 41 or second elastic beams 51. The two sets of elastic beams are arranged in an alternating pattern on the circumference, which satisfies the optimal angle for uniform stress field distribution, avoids the overlap of stress transmission paths, further reduces the measurement error caused by load superposition, and improves the linearity and repeatability of the sensor.

[0035] Following the previous example, the first group of elastic beams 4 includes four first elastic beams 41, and the second group of elastic beams 5 includes four second elastic beams 51. Along the circumferential direction, the angle between adjacent first elastic beams 41 and second elastic beams 51 is 45°.

[0036] In this embodiment, along the length direction of the first elastic beam 41, the first elastic beam 41 has a first end 411, a middle section 412 and a second end 413, and the thickness and width of the first end 411 and the second end 413 are both greater than the thickness and width of the middle section 412.

[0037] For details, please refer to Figure 1 and Figure 2 The length of the first elastic beam 41 is defined as L1, and the width as b1. The first end 411 of the first elastic beam 41 is connected to the edge of the central platform 1, and the second end 413 is connected to the inner edge of the inner ring 2. Along the length direction of the first elastic beam 41, the first elastic beam 41 has a variable cross-section structure. See details. Figure 3 The width b1 of the first elastic beam 41 is wider at both ends and narrower in the middle, and the width of the middle section 412 is the same throughout. See [reference needed]. Figure 4 The thickness h1 of the first elastic beam 41 is thicker at both ends and thinner in the middle, and the thickness of the middle section 412 is the same throughout. This setting allows tensile and compressive deformation to mainly occur in the middle section 412. The length L1, width b1 and thickness of the middle section 412 determine the tensile and compressive stiffness of the first elastic beam 41. While keeping the middle section 412 unchanged, the torsional stiffness of the first elastic beam 41 can be adjusted by adjusting the width and thickness of the first end 411 and the second end 413. Thus, the torsional stiffness can be independently increased while keeping the tensile and compressive stiffness unchanged, so that the first elastic beam 41 maintains high sensitivity to force loads and effectively suppresses crosstalk of moment loads, realizing dual-stage stiffness decoupling.

[0038] More specifically, according to the principles of mechanics of materials, the tensile and compressive stiffness of a beam is determined by its axial deformation, k f1 =EA / L, where E is the elastic modulus of the material, A is the cross-sectional area = b×h, b is the width, and h is the thickness; tensile and compressive deformation mainly occurs in the uniform cross-section region, i.e., the middle section 412. The first end 411 and the second end 413 serve as the roots of the first elastic beam 41. Because the axial stiffness of the roots of the larger cross-sections at both ends is much greater than that of the uniform cross-section region in the middle, a "series spring" effect is formed, making the overall tensile and compressive stiffness dominated by the weakest uniform cross-section region. By independently designing the width b and thickness h of the uniform cross-section region, the tensile and compressive stiffness k can be independently controlled. f1 This is also the basis for the fact that the force load is mainly sensitive to the deformation of the first set of elastic beams 4.

[0039] The torsional stiffness of a beam is determined by its torsional deformation, k t1=GJ / L, where G is the shear modulus of the material, and J is the torsional constant of the cross-section, which mainly depends on the shape and size ratio of the cross-section; for the torsional stiffness along the beam length, J=α1bh 3 For the torsional stiffness along the beam width, J = α1bh 3 For the torsional stiffness along the beam thickness direction, J=α1b 3 h, where α1 is the aspect ratio related coefficient, and the width is b and the thickness is h.

[0040] In summary, the tensile and compressive stiffness k of the first group of elastic beams 4 f1 ∝bh; Torsional stiffness k t1 ∝bh 3 Or b 3 h. Therefore, by using a variable cross-section design and independently adjusting the width b and thickness h, it is possible to maintain k. f Keeps the value unchanged, while significantly increasing k. t This ensures that the first set of elastic beams 4 maintains high sensitivity to force loads Fx, Fy and Fz, while effectively suppressing crosstalk of moment loads Mx, My and Mz, providing a structural basis for dual-stage stiffness decoupling.

[0041] In one optional embodiment, the first end 411 includes two symmetrically arranged ribs, and the second end 413 has the same structure as the first end 411. The two ends of the middle section 412 extend to the space between the two symmetrical ribs and are connected to the ribs that make up the first end 411 and the edge of the central platform 1, as well as to the ribs that make up the second end 413 and the inner edge of the inner ring 2. The width and thickness of the first end 411 or the second end 413 can be adjusted by adjusting the width and thickness of the ribs.

[0042] In one alternative embodiment, both the first end 411 and the second end 413 have rounded corners. The corner radius can be designed according to the external load to reduce stress levels and improve operational reliability. Similarly, both ends of the second elastic beam 51 can also have rounded corners for the same effect.

[0043] In this embodiment, along the thickness direction of the first elastic beam 41, the first elastic beam 41 has two parallel first surfaces 4121, which are used to mount strain gauges; along the thickness direction of the second elastic beam 51, the second elastic beam 51 has two parallel second surfaces 511, which are used to mount strain gauges, and the plane containing the second surfaces 511 is perpendicular to the plane containing the first surfaces 4121.

[0044] Specifically, the length directions of the multiple first elastic beams 41 correspond to different radial directions, and the first surfaces 4121 on the same side of the multiple first elastic beams 41 are located in the same plane. Similarly, the length directions of the multiple second elastic beams 51 correspond to different radial directions, and the second surface 511 of each second elastic beam 51 is perpendicular to the plane containing the first surface 4121. This arrangement allows the strain gauges on the first elastic beams 41 and the second elastic beams 51 to be located in two mutually orthogonal planes. The strain gauges on the first elastic beams 41 are mainly sensitive to the tensile, compressive, and shear deformations of the first elastic beams 41 in their own plane, that is, the deformations caused by force loads. The strain gauges on the second elastic beams 51 are mainly sensitive to the bending and torsional deformations of the second elastic beams 51 in the direction perpendicular to the plane of the first elastic beams 41, that is, the deformations caused by moment loads. This effectively reduces crosstalk between the two types of signals, improves the decoupling effect and measurement accuracy.

[0045] like Figure 1 , Figure 2 and Figure 4 As shown, in this embodiment, the inner edge of the outer ring 3 is provided with at least two first limiting parts 61, and the outer edge of the inner ring 2 is provided with at least two second limiting parts 62. The number of second limiting parts 62 and first limiting parts 61 is the same, and the second limiting parts 62 and first limiting parts 61 are arranged in a one-to-one correspondence. There is a gap between the first limiting parts 61 and the second limiting parts 62. When the second set of elastic beams 5 undergoes bending and / or torsional deformation at a predetermined angle, the first limiting parts 61 and the second limiting parts 62 abut against each other.

[0046] Specifically, the gap between the first limiting part 61 and the second limiting part 62 allows the inner ring 2 to rotate relative to the outer ring 3, enabling the second elastic beam 51 to bend and / or torsion within a predetermined angle. The predetermined angle of bending and / or torsion refers to the limit deformation of the second set of elastic beams 5, and the predetermined angle can be set according to the actual situation. When the moment load applied to the center platform 1 reaches or exceeds the maximum load, the first limiting part 61 and the second limiting part 62 abut against each other, preventing the inner ring 2 from rotating further relative to the outer ring 3, thereby preventing the second elastic beam 51 from bending and / or torsion further, achieving overload protection for the second elastic beam 51 and preventing damage to the second elastic beam 51.

[0047] For example, when there are two first limiting parts 61, the two first limiting parts 61 are located in the extension direction of the two adjacent first elastic beams 41 respectively. In this embodiment, the angle between the two first limiting parts 61 is 90°. The two second limiting parts 62 are arranged one-to-one with the two first limiting parts 61. When the center platform 1 is loaded with a moment load in the Mx direction and the maximum load is reached, one set of first limiting parts 61 and second limiting parts 62 abuts. When the center platform 1 is loaded with a moment load in the My direction and the maximum load is reached, the other set of first limiting parts 61 and second limiting parts 62 abuts. When the center platform 1 is loaded with a moment load in the Mz direction and the maximum load is reached, both sets of first limiting parts 61 and second limiting parts 62 abut. Of course, when multiple moment loads in multiple directions are superimposed, the corresponding first limiting parts 61 and second limiting parts 62 can still abut, thereby achieving overload protection for the second elastic beam 51.

[0048] In one optional embodiment, four first limiting parts 61 and four second limiting parts 62 are provided. The angle between two adjacent first limiting parts 61 is 90°. The positions of the second limiting parts 62 and the first limiting parts 61 correspond, and the angle between two adjacent second limiting parts 62 is also 90°. Similar to the working principle described above, when four first limiting parts 61 are provided, when the center platform 1 is loaded with a torque load in the Mx or My direction and reaches its maximum load, at least two sets of first limiting parts 61 and second limiting parts 62 simultaneously abut. When the center platform 1 is loaded with a torque load in the Mz direction and reaches its maximum load, all four sets of first limiting parts 61 and second limiting parts 62 can simultaneously abut. This arrangement can further improve the overload protection effect.

[0049] In this embodiment, both the first limiting part 61 and the second limiting part 62 are boss structures. The first limiting part 61 and the second limiting part 62 have two opposing surfaces. When the torque load applied to the center platform 1 reaches or exceeds the maximum load, the opposing surfaces of the first limiting part 61 and the second limiting part 62 abut against each other, preventing the inner ring 2 from rotating further relative to the outer ring 3. For example, in this embodiment, the elastic body is assembled in a robot joint. When the robot joint suddenly stalls, the second set of elastic beams 5 undergoes torsional deformation, and the inner ring 2 rotates relative to the outer ring 3. When the torque load exceeds the maximum load, the corresponding surfaces of the first limiting part 61 and the second limiting part 62 make hard contact. Thereafter, the additional torque is directly transmitted to the outer ring 3 through the two surfaces, and the stress of the second set of elastic beams 5 is limited to below the allowable stress, preventing excessive torsional deformation.

[0050] In this embodiment, the central platform 1, the first set of elastic beams 4, the inner ring 2, the second set of elastic beams 5, and the outer ring 3 are integrally formed.

[0051] In this embodiment, the central platform 1 is provided with a first positioning hole 11, which is used to connect an external movable structure, and the outer ring 3 is provided with a second positioning hole 31, which is used to connect an external fixed structure.

[0052] In this embodiment, the central platform 1 is also provided with a plurality of mounting holes 12. The plurality of mounting holes 12 are arranged around the first positioning hole 11 at a uniform angle. For example, the central platform 1 can be configured as a cuboid structure, and the upper surface of the central platform 1 is a square structure. The first positioning hole 11 is located at the center of the upper surface, and the four mounting holes 12 are located at the corners of the upper surface. The first positioning hole 11 and the mounting holes 12 are both used to connect to external movable structures, thereby improving the reliability of the connection state.

[0053] In this embodiment, the outer ring 3 is provided with a plurality of second positioning holes 31, the number of second positioning holes 31 corresponding to the number of first limiting parts 61. Each first limiting part 61 is provided with a second positioning hole 31. Since the first limiting part 61 is a boss structure, the first limiting part 61 has sufficient length, width and thickness, and sufficient rigidity. This arrangement can not only ensure the reliability of the connection between the outer ring 3 and the external fixing structure, but also improve the utilization rate of the installation space.

[0054] Secondly, the present invention provides a six-dimensional force sensor, including the above-mentioned elastic body, and also including a strain gauge group, the strain gauge group including multiple strain gauges, the multiple strain gauges being respectively mounted on a first set of elastic beams 4 and a second set of elastic beams 5.

[0055] The structure, connection relationship, and beneficial effects of the elastomer in this embodiment have been described in detail above. By using the elastomer described above as the sensitive substrate and arranging strain gauges on two sets of elastic beams to form a strain gauge group, the structural hard decoupling characteristics of the elastomer itself for force load and moment load are fully utilized. This allows the force signal and moment signal to be sensed by strain gauges at different positions and on different surfaces. This reduces interdimensional coupling from the sensor sensing principle level and has the advantages of high sensitivity, low cross-interference, strong overload resistance, and good dynamic performance. It can meet the needs of high-precision six-dimensional force measurement in fields such as robotics, automation, and aerospace.

[0056] See Figure 5In this embodiment, the strain gauges on the first set of elastic beams 4 form three sets of full-bridge circuits to measure Fx, Fy and Fz respectively, and the strain gauges on the second set of elastic beams 5 form three sets of full-bridge circuits to measure Mx, My and Mz respectively. For example, the first group of elastic beams 4 includes four first elastic beams 41, and the second group of elastic beams 5 includes four second elastic beams 51. A total of 24 strain gauges are provided, with 12 strain gauges in each group of elastic beams. The 12 strain gauges are respectively attached to the first surface 4121 of the first elastic beam 41 and the 12 strain gauges are respectively attached to the second surface 511 of the second elastic beam 51. The 24 strain gauges are defined as R1, R2, R3...R24. Strain gauges R1, R2, R3, and R4 form the full-bridge measurement Fx; strain gauges R5, R6, R7, and R8 form the full-bridge measurement Fy; strain gauges R9, R10, R11, and R12 form the full-bridge measurement Fz; strain gauges R13, R14, R15, and R16 form the full-bridge measurement Mx; strain gauges R17, R18, R19, and R20 form the full-bridge measurement My; and strain gauges R21, R22, R23, and R24 form the full-bridge measurement Mz. Calculating stress using strain gauge measurements is a mature technology and will not be discussed in detail here.

[0057] It should be noted that the first set of elastic beams 4 is a variable cross-section structure, with larger cross-sectional dimensions at both ends and a constant cross-section region in the middle, namely the first end 411, the second end 413, and the middle section 412 mentioned above. The region of maximum stress is located in the constant cross-section region near the beginning of the root transition fillet, not at the root itself. Strain gauges are arranged in this region along the beam length, 1-2 mm from the end of the root transition fillet, and attached to the upper or lower surface shown in the figure along the cross-sectional height. Both the upper and lower surfaces are the first surface 4121, which is farthest from the neutral axis and has the largest bending strain, thus obtaining the maximum strain output sensitivity. For the second set of elastic beams 5, according to the fourth strength theory, the maximum equivalent stress is located on the side near the fixed end. Strain gauges are arranged on the two sides shown in the figure, not on the upper or lower surface. Both sides are the second surface 511, and the edge of the strain gauge is located 1-2 mm from the connection end of the inner ring 2. The upper and lower surfaces and the two sides are located in two orthogonal planes, achieving structural-level spatial separation of force and torque signals.

[0058] To clearly illustrate the beneficial effects of the elastomer structure provided in this embodiment, simulation experiments and other methods are presented below. Figure 6 , Figure 7 , Figure 8 , Figure 9 The simulation results shown are illustrated with examples.

[0059] In the simulation experiment, the second positioning hole 31 of the outer ring 3 is fixedly constrained, and the specified force load and moment load are applied to the central platform 1. The specific force load and moment load are shown in the table below.

[0060]

[0061] Figure 6 The strain of the elastic body in this embodiment under the load Fx is shown. The first set of elastic beams 4 represents the region of maximum strain; the second set of elastic beams 5 represents the region of moderate strain; the inner ring 2 exhibits uniform and low strain, verifying its rigid body translational characteristics; the outer ring 3 has almost zero strain, verifying its fixed-end function. Since the elastic body is symmetrical about the coordinate axes, the analyses of Fy and Fx are identical. The strain distribution verifies the load-bearing mechanism of the two-stage series structure: the first set of elastic beams 4 dominates deformation, the second set of elastic beams 5 provides elastic constraint, and the stress is coordinated and transferred by the inner ring 2.

[0062] Figure 7 The strain of the elastic body in this embodiment under the Fz load is mainly observed in the first set of elastic beams 4, which verifies the main load-bearing characteristics of the first set of elastic beams 4.

[0063] Figure 8 The strain of the elastic body in this embodiment under the load Mx is shown. The strain mainly occurs in the second group of elastic beams 5, and the strain ratio with that of the first group of elastic beams 4 is greater than 4 times. This verifies that the second group of elastic beams 5 mainly bears the deformation caused by the moment load. The inner ring 2 realizes the graded transfer of load. Since the elastic body is symmetrical about the coordinate axis, the analysis of My and Mx is exactly the same.

[0064] Figure 9 The strain of the elastic body in this embodiment under the Mz load is shown. Similarly, the strain mainly occurs in the second group of elastic beams 5, and the strain ratio with that of the first group of elastic beams 4 is greater than 6 times. This verifies that the second group of elastic beams 5 mainly bears the deformation caused by the moment load. The inner ring 2 realizes the graded transfer of load.

[0065] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An elastic body for a six-dimensional force sensor, characterized in that, include: Central station (1); Inner ring (2) surrounds the central platform (1); The outer ring (3) surrounds the inner ring (2), and the central platform (1), inner ring (2) and outer ring (3) are arranged concentrically; The first set of elastic beams (4) connects the inner edge of the inner ring (2) and the central platform (1). The second set of elastic beams (5) connects the inner edge of the outer ring (3) and the outer edge of the inner ring (2). The torsional stiffness of the first set of elastic beams (4) is greater than that of the second set of elastic beams (5). When the central platform (1) is subjected to force, the first set of elastic beams (4) is adapted to undergo shear and / or tensile and compressive deformation under the action of force load, and the central platform (1) translates relative to the inner ring (2); the second set of elastic beams (5) is adapted to undergo bending and / or torsional deformation under the action of moment load, and the inner ring (2) rotates relative to the outer ring (3).

2. The elastic body of the six-dimensional force sensor according to claim 1, characterized in that, The torsional stiffness ratio of the second set of elastic beams (5) and the first set of elastic beams (4) ranges from 1:4 to 1:

6.

3. The elastic body of the six-dimensional force sensor according to claim 2, characterized in that, The first set of elastic beams (4) includes multiple first elastic beams (41), which are arranged at a uniform angle along the circumference. The second set of elastic beams (5) includes multiple second elastic beams (51), which are arranged at a uniform angle along the circumference. The number of first elastic beams (41) and second elastic beams (51) is the same.

4. The elastic body of the six-dimensional force sensor according to claim 3, characterized in that, Along the circumferential direction, multiple first elastic beams (41) and multiple second elastic beams (51) are arranged in an alternating manner, and the angle between two adjacent first elastic beams (41) and second elastic beams (51) is 360° / (2n), where n is the number of first elastic beams (41) or second elastic beams (51).

5. The elastic body of the six-dimensional force sensor according to claim 3, characterized in that, Along the length direction of the first elastic beam (41), the first elastic beam (41) has a first end (411), a middle section (412) and a second end (413), the thickness and width of the first end (411) and the second end (413) are both greater than the thickness and width of the middle section (412).

6. The elastic body of the six-dimensional force sensor according to claim 3, characterized in that, Along the thickness direction of the first elastic beam (41), the first elastic beam (41) has two parallel first surfaces (4121) for mounting strain gauges. Along the thickness direction of the second elastic beam (51), the second elastic beam (51) has two parallel second surfaces (511) for mounting strain gauges, and the second surfaces (511) are perpendicular to the plane containing the first surface (4121).

7. The elastic body of the six-dimensional force sensor according to any one of claims 1 to 6, characterized in that, The inner edge of the outer ring (3) is provided with at least two first limiting parts (61), and the outer edge of the inner ring (2) is provided with at least two second limiting parts (62). The number of second limiting parts (62) and first limiting parts (61) is the same, and the second limiting parts (62) and first limiting parts (61) are arranged in a one-to-one correspondence. There is a gap between the first limiting parts (61) and the second limiting parts (62). When the second set of elastic beams (5) undergoes bending and / or torsional deformation at a predetermined angle, the first limiting parts (61) and the second limiting parts (62) abut against each other.

8. The elastic body of the six-dimensional force sensor according to any one of claims 1 to 6, characterized in that, The central platform (1) is provided with a first positioning hole (11), which is used to connect an external movable structure. The outer ring (3) is provided with a second positioning hole (31), which is used to connect an external fixed structure.

9. A six-dimensional force sensor, characterized in that, The elastic body includes any one of claims 1 to 8, and further includes a strain gauge group, the strain gauge group including a plurality of strain gauges, the plurality of strain gauges being respectively mounted on the first group of elastic beams (4) and the second group of elastic beams (5).

10. The six-dimensional force sensor according to claim 9, characterized in that, The strain gauges on the first set of elastic beams (4) form three sets of full-bridge circuits to measure Fx, Fy and Fz respectively. The strain gauges on the second set of elastic beams (5) form three sets of full-bridge circuits to measure Mx, My and Mz respectively.

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