Torque sensor

Abstract

The invention relates to a torque sensor, which comprises a composite elastomer, the composite elastomer comprises an outer ring body and an inner ring body which are annular and are concentrically arranged, and a plurality of strain beams which are distributed along the circumferential direction and are radially connected between the outer ring body and the inner ring body, the torque sensor also comprises an optical fiber for detecting a torque signal, and the optical fiber is internally provided with a plurality of Bragg gratings; and the optical fiber alternately passes through the outer ring body and the inner ring body and is suspended and wound on the composite elastomer in an anchor point winding manner. The torque sensor can simplify a setting operation of an optical fiber for detecting a torque signal while avoiding a chirp problem.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a torque sensor. Background Art

[0002] A force sensor is a device that converts the magnitude of a force into a corresponding electrical signal. Force is the direct cause of changes in the motion of matter. Force sensors can measure the force or torque applied to them. Multi-axis force sensors can measure force or torque in multiple spatial directions. Force sensors are widely used in industrial and scientific fields such as robotics, manufacturing, aerospace, medicine, and civil engineering.

[0003] A torque sensor is a force sensor that can be used to form a force-controlled joint module on a robot's joint module. For example, the Chinese invention patent application "Joint Torque Sensor and Robot," with publication number CN120253028A (application number 202510221688.4), and the Chinese invention patent application "A Torque Sensor and Its Implementation Method," with publication number CN120121188A (application number 202510282245.6), disclose torque sensors that include a composite elastomer and a sensing strain gauge. The composite elastomer includes an outer retaining ring, an inner retaining ring, and a strain beam. The sensing strain gauge is printed or attached to the strain beam. When the strain beam is subjected to torque, it deforms slightly, causing the resistance of the strain gauge to change. This resistance change is converted into a voltage change through a Wheatstone bridge circuit. After amplification, filtering, and other signal processing circuits, an electrical signal proportional to the torque is generated, ultimately resulting in the torque measurement result. However, torque sensors with this structure have the following problems: 1. The sensor strain gauge needs to be printed or attached to the strain beam, and the operation process is relatively complicated. In particular, when the strain gauge needs to be set by pasting, workers need to operate under a microscope, which is difficult and will affect the production efficiency of the torque sensor; 2. The sensor strain gauge is printed or attached to the strain beam. Any slight stretch at any small position on the strain beam will affect the detection signal, resulting in chirping problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a torque sensor that can simplify the setting operation of the optical fiber used to detect the torque signal and avoid the chirp problem in the above-mentioned prior art.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: a torque sensor includes a composite elastomer, the composite elastomer including an outer ring body and an inner ring body arranged concentrically in an annular shape, and a plurality of strain beams distributed along the circumference and radially connected between the outer ring body and the inner ring body, and also includes an optical fiber for detecting torque signals, the optical fiber having a plurality of Bragg gratings therein;

[0006] The optical fiber passes through the outer ring body and the inner ring body alternately and is suspended on the composite elastic body in a winding manner through anchor points.

[0007] For convenient winding, a plurality of first protrusions are protruded along the circumferential direction on the outer ring body, and a plurality of second protrusions are protruded along the circumferential direction on the inner ring body. The first protrusions and the second protrusions are staggered along the circumferential direction. The optical fiber is alternately passed through the first protrusions and the second protrusions and is wound on the composite elastomer. There is a Bragg grating in the optical fiber between each first protrusion and the second protrusion.

[0008] Optionally, each first protrusion is correspondingly provided at a radially outer end of each strain beam;

[0009] And / or each second protrusion is correspondingly arranged at the radial inner end of each strain beam.

[0010] In order to avoid damaging the optical fiber, the first and second convex columns are formed into arc surfaces at the locations corresponding to the winding of the optical fiber.

[0011] In order to improve the fixing stability of the optical fiber on the composite elastomer, the optical fiber is fixed on the first convex column and the second convex column by point bonding.

[0012] In order to prevent the optical fiber from being excessively bent and affecting signal transmission loss, the optical fiber is wound around the second protrusion at an angle greater than 90°.

[0013] Preferably, the winding angle of the optical fiber on the first protrusion is greater than 90°.

[0014] In order to facilitate the arrangement of optical fibers, a through hole is provided at the center of the inner ring body, and a through hole is provided radially through the inner ring body for the ends of the optical fibers to pass through.

[0015] Compared to existing technologies, the present invention offers advantages in that its torque sensor utilizes a fiber Bragg grating (FBG) as the sensing component for detecting torque signals. During operation, relative torsion between the inner and outer rings causes the fiber Bragg grating (FBG) attached to the inner and outer rings to deform, either tensilely or compressively. Changes in the FBG data accurately measure the applied torque. The optical fiber in the present invention is suspended on the composite elastic body via an anchor winding method, making the winding process simple and requiring no additional equipment. Furthermore, the fiber's contact with the inner and outer rings is point-to-point, meaning the fiber as a whole only senses "average tension" or "global strain," avoiding small local variations that are transferred to the FBG. This avoids the chirp problem caused by "non-uniform strain." Compared to methods where the sensing component is affixed to a strain beam, this suspended fiber winding arrangement increases the fiber's deformation when the inner and outer rings experience relative torsion, improving the sensitivity of the detection data and, consequently, the accuracy of the test results. In addition, the structure based on the composite elastomer, combined with the suspended and wound optical fiber, can achieve structural decoupling, making the composite elastomer sensitive only to axial forces, thereby producing displacements and deformations far greater than those in other directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a three-dimensional diagram of a torque sensor in an embodiment of the present invention.

[0017] Figure 2 3D is a perspective view of another torque sensor according to an embodiment of the present invention.

[0018] Figure 3 FIG. 4 is a perspective view of another torque sensor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0020] like Figures 1 to 3 As shown, the torque sensor in this embodiment includes a composite elastomer 100 and an optical fiber 200 .

[0021] The composite elastomer 100 includes an annular, concentrically arranged outer ring 101 and inner ring 102, as well as a plurality of strain beams 103 distributed circumferentially and radially connected between the outer ring 101 and the inner ring 102. The number of strain beams 103 is set as needed; in this embodiment, four strain beams 103 are provided. During use, the inner ring 102 is connected to one joint module, and the outer ring 101 is connected to another joint module. When the two joint modules move relative to each other, the torque sensor can detect the relative torque between the two joint modules, facilitating precise control of the two joint modules.

[0022] The optical fiber 200 is used to detect torque signals. There are multiple Bragg gratings 201 inside the optical fiber 200. The Bragg wavelength of each Bragg grating 201 is different, which makes it easy to distinguish the detection signals of different Bragg gratings 201 and avoid signal overlap.

[0023] In this embodiment, the optical fiber 200 alternately passes through the outer ring body 101 and the inner ring body 102 and is suspended around the composite elastic body 100 via anchor winding. Specifically, a plurality of first protrusions 300 are uniformly circumferentially protruded from the outer ring body 101, and a plurality of second protrusions 400 are uniformly circumferentially protruded from the inner ring body 102. The positions of these first and second protrusions 300 and 400 match the position of the strain beam 103, either corresponding to the position of the strain beam 103 or being arranged on both sides of the strain beam 103, thereby facilitating light winding around them and detecting the strain signal.

[0024] In this embodiment, the first and second protrusions 300 and 400 are staggered along the circumference. The optical fiber 200 is wound around the composite elastomer 100 by alternately passing through each of the first and second protrusions 300 and 400. A Bragg grating 201 is provided in the optical fiber 200 between each of the first and second protrusions 300 and 400. To avoid damage to the optical fiber 200, the winding locations of each of the first and second protrusions 300 and 400 corresponding to the optical fiber 200 are curved. This prevents excessive bending of the optical fiber 200 when passing through the first and second protrusions 300 and 400. In this embodiment, the cross-sections of the first and second protrusions 300 and 400 are circular or semicircular. To improve the stability of the optical fiber 200 on the composite elastic body 100, the optical fiber 200 is fixed to the first and second protrusions 300, 400 by point bonding. That is, during winding, as the optical fiber 200 passes through each of the first and second protrusions 300, 400, which serve as winding anchor points, adhesive is applied at the contact points between the optical fiber 200 and the first and second protrusions 300, 400 to better secure the optical fiber 200. Of course, the optical fiber 200 is in a straight state when wound around the first and second protrusions 300, 400, and can be well fixed to the composite elastic body 100 without bonding.

[0025] In order to avoid excessive bending of the optical fiber 200 and thus affecting signal transmission loss, when the optical fiber 200 is wound on the first boss 300 and the second boss 400, the positions of the first boss 300 and the second boss 400 are reasonably set, and the winding angle of the optical fiber 200 on the first boss 300 and the second boss 400 is increased as much as possible without affecting the connection of the composite elastomer 100 to the joint module.

[0026] In this embodiment, three different arrangement positions of the first protruding pillar 300 and the second protruding pillar 400 are provided.

[0027] like Figure 1 As shown, in the first structure, each first protrusion 300 is disposed at the radially outer end of each strain beam 103, and each second protrusion 400 is disposed on the outer edge of the inner ring body 102, with each second protrusion 400 located between two adjacent first protrusions 300. The optical fiber 200 is wound around the outer side of each first protrusion 300 and the inner side of the second protrusion until it has wound around all first protrusions 300 and second protrusions 400 numbered 1 to 8. In this structure, the winding angle of the optical fiber 200 around the second protrusion 400 is greater than 90°, and the winding angle of the optical fiber 200 around the first protrusion 300 is greater than 60°. This prevents damage to the optical fiber 200 and has minimal impact on signal transmission loss within the optical fiber 200.

[0028] like Figure 2 As shown, in the second structure, each second protrusion 400 is correspondingly disposed at the radially inner end of each strain beam 103, each first protrusion 300 is disposed on the inner edge of the outer ring body 101, and each first protrusion 300 is located between two adjacent second protrusions 400. The optical fiber 200 is wound around the outer side surfaces of the first protrusions 300 and the outer side surfaces of the second protrusions until it is wound around all first protrusions 300 and second protrusions 400 numbered 1 to 8. In this structure, the winding angle of the optical fiber 200 around the second protrusions 400 is greater than 90°, while the winding angle of the optical fiber 200 around the first protrusions 300 is close to 90°, effectively preventing damage to the optical fiber 200 and having a minimal impact on signal transmission loss within the optical fiber 200.

[0029] like Figure 3 As shown, in the second structure, each first protrusion 300 is disposed at the radially outer end of the strain beam 103, and each second protrusion 400 is disposed at the radially inner end of each strain beam 103. The first and second protrusions 300 and 400 are alternately disposed on two adjacent strain beams 103. The optical fiber 200 is wound around the outer side surfaces of the first protrusions 300 and the outer side surfaces of the second protrusions until it passes through all first protrusions 300 and second protrusions 400 numbered 1 to 8. The optical fiber 200 is wound around the first and second protrusions 300, 400 at an angle greater than 90°, effectively preventing damage to the optical fiber 200 and minimizing signal transmission loss within the optical fiber 200.

[0030] In addition, in order to facilitate the arrangement of the optical fiber 200, a through hole 1021 is provided in the center of the inner ring body 102, and a through hole 1022 is provided radially through the inner ring body 102 for the end of the optical fiber 200 to pass through, that is, two transmissions are provided in the inner ring body 102 to fix the two ends of the optical fiber 200 respectively, so that both ends of the optical fiber 200 can pass through the through hole 1021 and route together with other wiring harnesses.

[0031] The torque sensor of the present invention uses a fiber grating (FBG) 200 as the detection component for torque signals. When the inner and outer rings 102 and 101 experience relative torsion, the fiber gratings (FBGs) affixed to the inner and outer rings undergo tensile or compressive deformation. The applied torque can be accurately measured by the changes in FBG data. The fiber 200 of the present invention is suspended around the composite elastomer 100 using an anchor winding method. This simple winding operation requires no additional equipment. Furthermore, the fiber 200 makes point contact with the inner and outer rings 102 and 101. Therefore, the fiber 200 as a whole only senses "average tension" or "global strain," avoiding small local variations that are transferred to the FBGs. This avoids the chirping problem caused by "non-uniform strain." Compared to an arrangement where the detection component is affixed to the strain beam 103, the suspended winding of the optical fiber 200 increases the deformation of the optical fiber 200 when the inner and outer rings 102, 101 experience phase twist, improving the sensitivity of the detection data and, consequently, the accuracy of the test results. Furthermore, the structure of the composite elastomer 100, combined with the suspended winding of the optical fiber 200, achieves structural decoupling, making the composite elastomer 100 sensitive only to axial forces, thereby generating significantly greater displacement and deformation than in other directions.

[0032] In the present specification and claims, directional terms such as "front," "back," "up," "down," "left," "right," "side," "top," and "bottom" are used to describe various exemplary structural parts and components of the present invention. However, these terms are used herein for convenience of description only and are based on the exemplary orientations shown in the accompanying drawings. Because the embodiments disclosed herein can be arranged in various orientations, these directional terms are intended for illustrative purposes only and should not be construed as limiting. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

Claims

1. A torque sensor comprising a composite elastic body (100), wherein the composite elastic body (100) comprises an outer ring body (101) and an inner ring body (102) arranged concentrically in an annular shape, and a plurality of strain beams (103) distributed along the circumferential direction and radially connected between the outer ring body (101) and the inner ring body (102), characterized in that: It also includes an optical fiber (200) for detecting torque signals, wherein the optical fiber (200) has a plurality of Bragg gratings (201) inside. The optical fiber (200) alternately passes through the outer ring body (101) and the inner ring body (102) and is suspended on the composite elastic body (100) by means of anchor point winding.

2. The torque sensor according to claim 1, wherein: The outer ring body (101) is provided with a plurality of first convex pillars (300) along the circumferential direction, and the inner ring body (102) is provided with a plurality of second convex pillars (400) along the circumferential direction. The first convex pillars (300) and the second convex pillars (400) are staggered along the circumferential direction. The optical fiber (200) is wound around the composite elastic body (100) by alternately passing through each first convex pillar (300) and the second convex pillar (400). A Bragg grating (201) is provided in the optical fiber (200) between each first convex pillar (300) and the second convex pillar (400).

3. The torque sensor according to claim 2, wherein: Each first protrusion (300) is correspondingly arranged at a radially outer end of each strain beam (103); And / or each second protrusion (400) is correspondingly arranged at the radial inner end of each strain beam (103).

4. The torque sensor according to claim 3, wherein: The winding positions of the first convex column (300) and the second convex column (400) corresponding to the optical fiber (200) are arc surfaces.

5. The torque sensor according to claim 4, characterized in that: The optical fiber (200) is fixed on the first convex column (300) and the second convex column (400) by point bonding.

6. The torque sensor according to any one of claims 2 to 5, characterized in that: The optical fiber (200) is wound around the second protruding column (400) at an angle greater than 90°.

7. The torque sensor according to claim 6, characterized in that: The winding angle of the optical fiber (200) on the first protruding column (300) is greater than 90°.

8. The torque sensor according to any one of claims 1 to 5, characterized in that: A through hole (1021) is provided at the center of the inner ring body (102), and a through hole (1022) is provided radially through the inner ring body (102) for the end of the optical fiber (200) to pass through.

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