Non-straight elastic beam structure and six-dimensional force sensor adopting same

Abstract

The present application relates to the technical field of force sensor, especially to a non-linear elastic beam structure and a six-dimensional force sensor adopting the same. The main purpose of the present application is to solve the problem that the existing force sensor is sensitive to force measurement through bending deformation, and the thin sheet flexible hinge is arranged at the root to reduce the tension and compression stiffness, but the overload capacity of the sensor is greatly reduced, and it is difficult to be applied to the impact load scene of humanoid robot, etc. The technical scheme is as follows: the first cross beam and the connecting beam are arranged in L shape, the first cross beam and the connecting beam are equal cross section structure and are integrally formed, the far ends of the first cross beam and the connecting beam are force end and connecting end respectively, and a fixed included angle is formed between the first cross beam and the connecting beam. The present application can ensure the bending force measurement sensitivity of the force sensor, improve the overload capacity, adapt to the impact load scene of humanoid robot, etc., expand the application range and enhance the practicability.

Description

Technical Field

[0001] This invention relates to the field of force sensor technology, and in particular to a non-linear elastic beam structure and a six-dimensional force sensor using the structure. Background Technology

[0002] In the design and application of force sensors, given the high tensile and compressive stiffness of materials, utilizing bending deformation for force measurement has become the most ideal technical solution. This method can effectively achieve sensitive force detection and meet the measurement needs in most scenarios. Currently, most force sensors on the market adopt a three-beam or four-beam structure. In order to reduce the tensile and compressive stiffness of the beams themselves and enable the corresponding beam segments to generate sufficient bending deformation to complete force detection, the industry commonly uses the technique of setting thin-film flexible hinges at the root of the beam.

[0003] However, while the introduction of thin-film flexible hinges can reduce tensile and compressive stiffness and achieve sensitive force measurement, its weak structural strength significantly reduces the overload capacity of the entire sensor. This makes the sensor highly susceptible to damage under impact loads, hindering its application in complex working scenarios such as humanoid robots that require resistance to impact loads, thus limiting the applicability and practicality of force sensors. Therefore, this invention proposes a non-linear elastic beam structure and a six-dimensional force sensor using this structure. Summary of the Invention

[0004] The purpose of this invention is to address the problem in the prior art that existing force sensors measure force sensitively through bending deformation, and while thin-film flexible hinges are set at the root to reduce tensile and compressive stiffness, this significantly reduces the sensor's overload capacity and makes it difficult to apply to impact load scenarios such as humanoid robots. The invention proposes a non-linear elastic beam structure and a six-dimensional force sensor using this structure.

[0005] In a first aspect, the present invention proposes a non-linear elastic beam structure, wherein the elastic beam structure is non-linear and has at least two spaced strain detection zones; when the elastic beam structure is subjected to external force, at least a portion of the axial force or lateral force applied thereto is converted into bending moment acting on the strain detection zones; the strain detection zones are used to detect the strain generated by the bending moment and / or the directly acting tensile and compressive loads.

[0006] Optionally, an L-shaped non-linear elastic beam structure is included, formed by an L-shaped arrangement of a first crossbeam and a connecting beam. Both the first crossbeam and the connecting beam are of equal cross-section and integrally formed. The ends of the first crossbeam and the connecting beam that are furthest apart are the force-bearing end and the connection end, respectively, and a fixed angle is formed between the first crossbeam and the connecting beam. When a concentrated force F and a moment M are applied to the force-bearing end, a bending moment Mh is generated on the connecting beam, and a moment Ml is generated at the first crossbeam. The bending moment Mh satisfies the relationship: Mh=M+F×h×sinθ, where h is the length from the force-bearing end to the center of the connecting beam patch, and θ is the angle between the first crossbeam and the connecting beam. The moment Ml satisfies the relationship Ml=M+F×L×sinθ, where L is the axial distance from the force-bearing end to the first crossbeam. The following can be calculated: F=(Ml-Mh) / [(Lh)sinθ], M=(Ml+Mh-F(L+h)sinθ) / 2.

[0007] Optionally, the non-linear elastic beam structure is an arc-shaped structure, with strain gauges installed at both ends of the arc-shaped structure to form a half-bridge. When a concentrated force F and a moment M are applied to the stressed end, a bending moment Mh and a moment Ml are generated at both ends of the arc-shaped structure. The bending moment Mh satisfies the relationship: Mh = M + F × h × sinθ, where h is the length from the stressed end to the center of the patch near the stressed end, and θ is the angle between the center lines of the patches at both ends of the arc-shaped structure. The moment Ml satisfies the relationship Ml = M + F × L × sinθ, where L is the axial distance from the stressed end to the center of the patch away from the stressed end. The following can be calculated: F = (Ml - Mh) / [(Lh)sinθ], M = (Ml + Mh - F(L + h)sinθ) / 2.

[0008] Optionally, a second crossbeam is also included, which is fixedly connected to the end of the connecting beam away from the first crossbeam. The first crossbeam, the connecting beam, and the second crossbeam are all of equal cross-section and integrally formed, forming a Z-shaped non-linear elastic beam structure. When force F and moment M are applied to the force-bearing end, the force Ml at the first crossbeam satisfies the relationship Ml=M+F×L×sinθ, where L is the distance from the force-bearing end to the axial direction of the first crossbeam, and the force at the second crossbeam is M. Solving for F, we get F=(Ml-M) / (Lsinθ). The first crossbeam and the second crossbeam are arranged in parallel, and the ends of the first crossbeam and the second crossbeam that are away from each other are the force-bearing end and the connecting end, respectively.

[0009] Secondly, the present invention proposes a six-dimensional force sensor employing a non-linear elastic beam structure, comprising a fixed end, a loading platform, and an elastic body. The elastic body is composed of at least three sets of non-linear elastic beam structures, each set of non-linear elastic beam structures being arranged in a circular array around the center of the loading platform. The connecting ends of each set of non-linear elastic beam structures are connected to the fixed end, and the force-bearing ends of each set of non-linear elastic beam structures are connected to the loading platform. Strain gauges are provided on the surfaces of the first and second crossbeams, and strain gauges are installed on the sides of the connecting beams of the L-shaped elastic beam structure.

[0010] Optionally, strain gauges are installed on the upper and lower surfaces of the first and second crossbeams to measure the vertical force Fz, and strain gauges at 45° and 135° angles to the beam segment axis are installed on the upper and lower surfaces of the first or second crossbeams to measure the torque Mz; the formula for measuring the vertical force Fz is: The formula for measuring torque Mz is: Where E is the modulus of elasticity, I is the moment of inertia of the beam segment section, L is the effective bending length of the beam segment, and y is the distance from the patch to the neutral layer. The equivalent strain of the entire bridge corresponding to the vertical force. This represents the equivalent strain of the entire bridge corresponding to the torque.

[0011] Optionally, the horizontal forces Fx and Fy are measured by bending deformation of the corresponding horizontally arranged beam segments. The horizontal forces Fx or Fy are transmitted through the connecting beam to form a bending moment M = F·H, where H is the height of the connecting beam. The formula for measuring the horizontal forces Fx or Fy is: , ,in , These are the equivalent strains of the full bridge corresponding to the horizontal forces Fx and Fy, respectively.

[0012] Optionally, the overturning moments Mx and My are measured by asymmetric bending strain of the corresponding horizontally arranged beam segments, and the measurement formula is as follows: , ,in , These are the full-bridge equivalent strains corresponding to the overturning moments Mx and My, respectively.

[0013] Optionally, the strain gauges are arranged axially along the beam segment and form a Wheatstone full-bridge circuit for temperature compensation and interference cancellation.

[0014] Optionally, the decoupling matrix between the six-dimensional force and the equivalent strain of each bridge circuit can be a diagonal matrix or a fully coupled matrix:

[0015]

[0016] Where the coefficients are: .

[0017] In summary, this application includes at least one of the following beneficial technical effects:

[0018] This invention utilizes a uniform cross-section structure of an elastic beam, eliminating weak links such as thin-plate flexible hinges, and can effectively withstand impact loads, making it suitable for complex working conditions such as humanoid robots.

[0019] Furthermore, by using the Z-shaped elastic beam structure, strain gauges only need to be attached to the upper and lower surfaces of the first and second crossbeams, eliminating the need to attach them to the sides of the beam. Combined with the integrated design of the Wheatstone full-bridge circuit, the difficulty of attaching the strain gauges is greatly reduced, enabling automated mass production and improving production efficiency and product consistency.

[0020] In summary, this invention, while ensuring the bending force measurement sensitivity of the force sensor, improves its overload capacity, enabling it to adapt to impact load scenarios such as humanoid robots, thus expanding its applicability and enhancing its practicality. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a six-dimensional force sensor employing an L-shaped non-linear elastic beam structure.

[0022] Figure 2 yes Figure 1 A diagram showing the view from below;

[0023] Figure 3 This is a schematic diagram of a six-dimensional force sensor that uses an arc-shaped, non-linear elastic beam structure.

[0024] Figure 4 This is a schematic diagram of a six-dimensional force sensor employing a Z-shaped non-linear elastic beam structure.

[0025] Figure 5 This is a schematic diagram of the circular fixed end structure;

[0026] Figure 6 This is a schematic diagram of a six-dimensional force sensor that uses three sets of Z-shaped non-linear elastic beam structures.

[0027] Figure label:

[0028] 1. Elastomer; 2. Fixed end; 3. Loading platform; 11. First crossbeam; 12. Connecting beam; 13. Second crossbeam. Detailed Implementation

[0029] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] The components of the embodiments of the invention described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0031] 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.

[0032] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Example 1, as Figure 1 and Figure 2 As shown, the present invention proposes a non-linear elastic beam structure. When the non-linear elastic beam structure is L-shaped, it includes a first crossbeam 11 and a connecting beam 12 arranged in an L-shape. Both the first crossbeam 11 and the connecting beam 12 are of equal cross-section and integrally formed. The ends of the first crossbeam 11 and the connecting beam 12 that are far apart are the force-bearing end and the connection end, respectively. A fixed angle θ is formed between the first crossbeam 11 and the connecting beam 12. This angle θ can be an acute angle, an obtuse angle, or a right angle, which is determined according to the sensor range and sensitivity requirements. When a concentrated force F and a moment M are applied to the stressed end, a bending moment Mh is generated on the connecting beam 12, and a moment Ml is generated at the first crossbeam 11. The bending moment Mh satisfies the relationship: Mh = M + F × h × sinθ, where h is the length from the stressed end to the center of the patch on the connecting beam 12, and θ is the angle between the first crossbeam 11 and the connecting beam 12. The moment Ml satisfies the relationship Ml = M + F × L × sinθ, where L is the axial distance from the stressed end to the first crossbeam 11. These can be calculated as follows:

[0035] F=(Ml-Mh) / [(Lh)sinθ], M=(Ml+Mh-F(L+h)sinθ) / 2.

[0036] Strain gauges are provided on the surfaces of the first crossbeam 11 and the connecting beam 12. The strain gauges are attached along the axial direction of the beam segment to the stress uniform area in the middle section of the upper and lower surfaces to pick up the strain signals generated by bending deformation.

[0037] A six-dimensional force sensor employing the aforementioned non-linear elastic beam structure includes a fixed end 2, a loading platform 3, and an elastic body 1. The fixed end 2 and the loading platform 3 can be manufactured in various shapes, such as circular or square, according to actual customer requirements. The elastic body 1 consists of at least three sets of non-linear elastic beam structures, each set arranged in a circular array around the center of the loading platform 3. Preferably, the three sets are symmetrically distributed at 120° intervals or the four sets are 90° intervals to ensure isotropic measurement characteristics. The connecting ends of each set of non-linear elastic beam structures are connected to the fixed end 2 and the loading platform 3. All units can be fixed by integral molding or by detachable means. The elastic body can be manufactured as a whole or separately and then installed. Using a modular processing method can significantly reduce manufacturing costs. The force-bearing ends of each set of non-linear elastic beam structures are connected to the loading platform 3, which is a central rigid platform used to bear external six-dimensional force / moment loads and uniformly transmit them to each elastic beam structure.

[0038] Strain gauges on the surface of the first crossbeam 11 are used to measure the vertical force Fz and torque Mz. The formula for measuring the vertical force Fz is: The formula for measuring torque Mz is: Where E is the elastic modulus and I is the moment of inertia of the beam segment. For a rectangular section, , For the width of the beam, y is the beam height. L is the effective bending length of the beam segment, referring to the distance from the center of the patch to the beam end constraint point. y is the distance from the patch to the neutral layer. For symmetrical patches on the upper and lower surfaces, . The equivalent strain of the entire bridge corresponding to the vertical force. The equivalent strain of the full bridge circuit is the torque, and each equivalent strain is obtained by calibration and conversion from the output voltage of the corresponding full bridge circuit.

[0039] Strain gauges on the sides of connecting beam 12 are used to measure horizontal forces Fx and Fy, as well as overturning moments Mx and My. The horizontal force Fx or Fy is transmitted through connecting beam 12, forming a bending moment M = F·H, where H is the height of connecting beam 12, i.e., the vertical distance between the upper and lower end faces of connecting beam 12, constituting the lever arm of the horizontal force on the neutral layer of the second crossbeam 13. The formula for measuring the horizontal force Fx or Fy is: , ,in , These are the equivalent strains of the full bridge corresponding to horizontal forces Fx and Fy, respectively. When Fx is applied, the two sets of elastic beam structures symmetrically arranged in the X direction produce opposite bending strains and are connected to the same full bridge differential output.

[0040] The overturning moments Mx and My are measured by asymmetric bending strain of the corresponding horizontally arranged beam segments, and the measurement formula is as follows: , ,in , These are the equivalent strains of the entire bridge corresponding to the overturning moments Mx and My, respectively. For example, Mx causes the two sets of elastic beams in the Y direction to produce opposite bending, one in tension and one in compression. The bending moment signal is extracted through the differential bridge circuit.

[0041] The decoupling matrix between the six-dimensional force and the equivalent strain of each bridge circuit is either a diagonal matrix or a fully coupled matrix. Under ideal manufacturing and symmetrical assembly conditions, there is no theoretical coupling between the dimensions, and a diagonal matrix can be directly used for calculation. In actual engineering, there are slight cross-couplings, requiring calibration to obtain a 6×6 fully coupled matrix for software decoupling. A diagonal matrix is ​​used under ideal symmetrical structures:

[0042]

[0043] Where the coefficients are: .

[0044] In this embodiment, when the non-linear elastic beam structure is L-shaped, its core load-bearing components are the first crossbeam 11 and the connecting beam 12. Both are of uniform cross-section and integrally formed, with no weak points, and can stably transmit external forces. During operation, an external concentrated force F is applied to the load-bearing end of the first crossbeam 11. The force is transmitted along the axial direction of the first crossbeam 11 to the connecting beam 12, which forms a fixed angle θ with the first crossbeam 11. According to the principles of mechanics, a bending moment M will be generated on the connecting beam 12. The magnitude of the bending moment satisfies the relationship: M = F × L × sinθ, where L is the distance from the load-bearing end to the axial direction of the first crossbeam 11, and θ is the angle between the first crossbeam 11 and the connecting beam 12.

[0045] When θ is adjusted to 90°, sinθ = 1, and the bending moment formula simplifies to M = F × L. At this point, the force transmission efficiency reaches its maximum, and both the connecting beam 12 and the first crossbeam 11 will undergo pure bending deformation. To accurately capture this bending deformation, strain gauges are attached axially along the beam segments in the stress uniformity zone at the midpoint of the upper and lower surfaces of the first crossbeam 11 and the connecting beam 12. The strain gauges convert the mechanical bending deformation of the beam into detectable electrical signals, providing basic data for subsequent force calculations.

[0046] The six-dimensional force sensor employing the aforementioned non-linear elastic beam structure comprises a fixed end 2, a loading platform 3, and an elastic body 1. The elastic body 1 consists of at least three sets of L-shaped or Z-shaped non-linear elastic beam structures. These sets are arranged in a circular array around the center of the loading platform 3, preferably with three sets spaced at 120° intervals or four sets spaced at 90° intervals to ensure the sensor's isotropic measurement characteristics. The connecting ends of each set of non-linear elastic beam structures are connected to the fixed end 2 and the loading platform 3. The connection method can be bolt fixing or integral molding and support to ensure the beam remains stable under load. The load-bearing ends of each set of non-linear elastic beam structures are connected to the loading platform 3, which is a central rigid platform. Its function is to bear the externally applied six-dimensional force / moment load and evenly distribute the load to each set of elastic beam structures, avoiding localized stress concentration.

[0047] The formula for measuring vertical force Fz is: The formula for measuring torque Mz is: . The equivalent strain of the entire bridge corresponding to the vertical force Fz is... The full-bridge equivalent strain corresponding to torque Mz is obtained by calibration and conversion of the output voltage of the corresponding Wheatstone full-bridge circuit.

[0048] When an external horizontal force Fx or Fy is applied to the loading platform 3, the force is transmitted through the first crossbeam 11 to the connecting beam 12, and a bending moment M = F·H is formed through the connecting beam 12, where H is the height of the connecting beam 12, i.e., the vertical distance between the upper and lower end faces of the connecting beam 12, constituting the lever arm of the horizontal force on the neutral layer of the second crossbeam 13. The formula for measuring the horizontal force Fx or Fy is: , ,in , These are the equivalent strains of the full bridge corresponding to horizontal forces Fx and Fy, respectively. When Fx is applied, the two sets of elastic beam structures symmetrically arranged in the X direction produce opposite bending strains. The signals collected by the strain gauges are connected to the same full bridge to achieve differential output, thereby improving measurement accuracy.

[0049] The formulas for measuring overturning moments Mx and My are: , ,in , These are the full-bridge equivalent strains corresponding to the overturning moments Mx and My, respectively. For example, when an overturning moment Mx is applied, the two sets of elastic beams in the Y direction will produce opposite bending deformations, one in tension and one in compression. The reverse strain signals collected by the strain gauges are extracted through a differential bridge circuit to obtain the relevant data of the overturning moment Mx. The measurement logic of My is the same as that of Mx.

[0050] Decoupling between the six-dimensional force and the equivalent strain of each bridge circuit is achieved through decoupling matrices, which are divided into diagonal matrices and fully coupled matrices. Under ideal machining and symmetrical assembly conditions, there is no theoretical coupling between the forces / torques in each dimension, and the signal conversion can be directly performed using a diagonal matrix to ensure the accuracy of the measurement results. In practical engineering applications, due to factors such as machining tolerances, patch position deviations, and load eccentricity, there will be slight cross-coupling between the dimensions. In this case, a 6×6 fully coupled decoupling matrix needs to be obtained through standard static calibration tests. Dimensional crosstalk is then eliminated through software calculations to further improve the measurement accuracy of the sensor.

[0051] Example 2, as Figure 3 As shown, based on Embodiment 1, the non-linear elastic beam structure is an arc-shaped structure. Strain gauges are installed at both ends of the arc-shaped structure to form a half-bridge. When a concentrated force F and a moment M are applied to the stressed end, a bending moment Mh and a moment Ml are generated at both ends of the arc-shaped structure. The bending moment Mh satisfies the relationship: Mh = M + F × h × sinθ, where h is the length from the stressed end to the center of the patch near the stressed end, and θ is the angle between the center lines of the patches at both ends of the arc-shaped structure. The moment Ml satisfies the relationship Ml = M + F × L × sinθ, where L is the axial distance from the stressed end to the patch away from the center of the patch. These can be calculated as follows:

[0052] F=(Ml-Mh) / [(Lh)sinθ], M=(Ml+Mh-F(L+h)sinθ) / 2.

[0053] The formula for measuring vertical force Fz is: The formula for measuring torque Mz is: Where E is the elastic modulus and I is the moment of inertia of the beam segment. For a rectangular section, , For the width of the beam, y is the beam height. L is the effective bending length of the beam segment, referring to the distance from the center of the patch to the beam end constraint point. y is the distance from the patch to the neutral layer. For symmetrical patches on the upper and lower surfaces, . The equivalent strain of the entire bridge corresponding to the vertical force. The equivalent strain of the full bridge circuit is the torque, and each equivalent strain is obtained by calibration and conversion from the output voltage of the corresponding full bridge circuit.

[0054] Strain gauges on the sides of the curved structure are also used to measure horizontal forces Fx and Fy, as well as overturning moments Mx and My. The horizontal force Fx or Fy generates a bending moment M = F·H, where H is the vertical distance between the centers of the two gauge locations on the curved structure. The formula for measuring the horizontal force Fx or Fy is: , ,in , These are the equivalent strains of the full bridge corresponding to horizontal forces Fx and Fy, respectively. When Fx is applied, the two sets of elastic beam structures arranged symmetrically in the X direction produce opposite bending strains and are connected to the same full bridge differential output.

[0055] The overturning moments Mx and My are measured by asymmetric bending strain of the corresponding horizontally arranged beam segments, and the measurement formula is as follows: , ,in , These are the equivalent strains of the entire bridge corresponding to the overturning moments Mx and My, respectively. For example, Mx causes the two sets of elastic beams in the Y direction to produce opposite bending, one in tension and one in compression. The bending moment signal is extracted through the differential bridge circuit.

[0056] The decoupling matrix between the six-dimensional force and the equivalent strain of each bridge circuit is either a diagonal matrix or a fully coupled matrix. Under ideal manufacturing and symmetrical assembly conditions, there is no theoretical coupling between the dimensions, and a diagonal matrix can be directly used for calculation. In actual engineering, there are slight cross-couplings, requiring calibration to obtain a 6×6 fully coupled matrix for software decoupling. A diagonal matrix is ​​used under ideal symmetrical structures:

[0057]

[0058] Where the coefficients are: .

[0059] In this embodiment, the formula for measuring the vertical force Fz is: The formula for measuring torque Mz is: . The equivalent strain of the entire bridge corresponding to the vertical force Fz is... The full-bridge equivalent strain corresponding to torque Mz is obtained by calibration and conversion of the output voltage of the corresponding Wheatstone full-bridge circuit.

[0060] When an external horizontal force Fx or Fy is applied to the loading platform 3, and a concentrated force F and a torque M are applied to the force-bearing end, a bending moment Mh and a torque Ml are generated at both ends of the arc-shaped structure. The bending moment Mh satisfies the relationship: Mh = M + F × h × sinθ, where h is the length from the force-bearing end to the center of the patch near the force-bearing end, and θ is the angle between the center lines of the patches at both ends of the arc-shaped structure. The torque Ml satisfies the relationship Ml = M + F × L × sinθ, where L is the axial distance from the force-bearing end to the center of the patch away from the force-bearing end. The following can be calculated: F = (Ml - Mh) / [(Lh)sinθ], M = (Ml + Mh - F(L + h)sinθ) / 2. The formula for measuring the horizontal force Fx or Fy is: , ,in , These are the equivalent strains of the full bridge corresponding to horizontal forces Fx and Fy, respectively. When Fx is applied, the two sets of elastic beam structures symmetrically arranged in the X direction produce opposite bending strains. The signals collected by the strain gauges are connected to the same full bridge to achieve differential output, thereby improving measurement accuracy.

[0061] The formulas for measuring overturning moments Mx and My are: , ,in , These are the full-bridge equivalent strains corresponding to the overturning moments Mx and My, respectively. For example, when an overturning moment Mx is applied, the two sets of elastic beams in the Y direction will produce opposite bending deformations, one in tension and one in compression. The reverse strain signals collected by the strain gauges are extracted through a differential bridge circuit to obtain the relevant data of the overturning moment Mx. The measurement logic of My is the same as that of Mx.

[0062] Decoupling between the six-dimensional force and the equivalent strain of each bridge circuit is achieved through decoupling matrices, which are divided into diagonal matrices and fully coupled matrices. Under ideal machining and symmetrical assembly conditions, there is no theoretical coupling between the forces / torques in each dimension, and the signal conversion can be directly performed using a diagonal matrix to ensure the accuracy of the measurement results. In practical engineering applications, due to factors such as machining tolerances, patch position deviations, and load eccentricity, there will be slight cross-coupling between the dimensions. In this case, a 6×6 fully coupled decoupling matrix needs to be obtained through standard static calibration tests. Dimensional crosstalk is then eliminated through software calculations to further improve the measurement accuracy of the sensor.

[0063] Example 3, please refer to Figures 4 to 6 Based on Embodiment 1, when the non-linear elastic beam structure is Z-shaped, in addition to the L-shaped structure, a second crossbeam 13 is fixedly connected to the end of the connecting beam 12 away from the first crossbeam 11. The first crossbeam 11, the connecting beam 12, and the second crossbeam 13 are all of equal cross-section and integrally formed, forming a Z-shaped non-linear elastic beam structure. When force F and moment M are applied to the stressed end, the force Ml at the first crossbeam 11 satisfies the relationship Ml=M+F×L×sinθ, where L is the axial distance from the stressed end to the first crossbeam 11, and the force at the second crossbeam 13 is M. Compared to the L-shaped elastic beam structure, it is easier to solve for F=(Ml-M) / (Lsinθ).

[0064] The first crossbeam 11 and the second crossbeam 13 are arranged parallel to each other, with the ends of the first crossbeam 11 and the second crossbeam 13 being the force-bearing end and the connection end, respectively. The force-bearing end of the first crossbeam 11 is connected to the loading platform 3, and the connection end of the second crossbeam 13 is connected to the fixed end 2. Strain gauges are provided on the upper and lower surfaces of the first crossbeam 11 and the second crossbeam 13. The strain gauges are arranged along the axial direction of the beam segment and form a Wheatstone full-bridge circuit for temperature compensation and interference cancellation. Each full-bridge circuit consists of four strain gauges. The strain gauges of adjacent bridge arms sense opposite bending strains, thereby doubling the output voltage and eliminating zero-point drift caused by changes in ambient temperature. Strain gauges at 45° and 135° to the axial direction of the beam segment are provided on the upper and lower surfaces of the first crossbeam 11 or the second crossbeam 13 for measuring torque Mz. The strain gauges are either resistance strain gauges or silicon-based MEMS piezoresistive strain gauges. Resistance strain gauges are suitable for conventional precision applications, while silicon-based MEMS piezoresistive strain gauges have higher sensitivity and are suitable for detecting minute strains.

[0065] It is worth mentioning that when using the Z-shaped elastic beam structure, only the top and bottom surfaces need to be patched, and no patching is required on the sides. This can be done through automated patching equipment, improving product production efficiency.

[0066] Strain gauges mounted on the upper and lower surfaces of the first crossbeam 11 are used to measure the vertical force Fz and torque Mz. The formula for measuring the vertical force Fz is: The formula for measuring torque Mz is: Where E is the elastic modulus and I is the moment of inertia of the beam segment. For a rectangular section, , For the width of the beam, y is the beam height. L is the effective bending length of the beam segment, referring to the distance from the center of the patch to the beam end constraint point. y is the distance from the patch to the neutral layer. For symmetrical patches on the upper and lower surfaces, . The equivalent strain of the entire bridge corresponding to the vertical force. The equivalent strain of the full bridge circuit is the torque, and each equivalent strain is obtained by calibration and conversion from the output voltage of the corresponding full bridge circuit.

[0067] Horizontal forces Fx and Fy are measured by bending deformation of the corresponding horizontally arranged beam segments. The horizontal force Fx or Fy is transmitted through connecting beam 12, forming a bending moment M = F·H, where H is the height of connecting beam 12, i.e., the vertical distance between the upper and lower end faces of connecting beam 12, constituting the lever arm of the horizontal force on the neutral layer of the second crossbeam 13. The formula for measuring horizontal force Fx or Fy is: , ,in , These are the equivalent strains of the full bridge corresponding to horizontal forces Fx and Fy, respectively. When Fx is applied, the two sets of elastic beam structures arranged symmetrically in the X direction produce opposite bending strains and are connected to the same full bridge differential output.

[0068] The overturning moments Mx and My are measured by asymmetric bending strain of the corresponding horizontally arranged beam segments, and the measurement formula is as follows: , ,in , These are the equivalent strains of the entire bridge corresponding to the overturning moments Mx and My, respectively. For example, Mx causes the two sets of elastic beams in the Y direction to produce opposite bending, one in tension and one in compression. The bending moment signal is extracted through the differential bridge circuit.

[0069] In this embodiment, the Z-shaped non-linear elastic beam structure is optimized based on the L-shaped non-linear elastic beam structure. Its core components include a first crossbeam 11, a connecting beam 12, and a second crossbeam 13 fixedly connected to the end of the connecting beam 12 away from the first crossbeam 11. All three are of equal cross-section and integrally formed, and the whole is arranged in a Z-shape. The first crossbeam 11 and the second crossbeam 13 are arranged in parallel.

[0070] During operation, the external load is transmitted through the force-bearing end of the first crossbeam 11 and stably transferred to the second crossbeam 13 via the connecting beam 12, causing directional bending deformation in both the first and second crossbeams 11 and 13. To improve measurement accuracy and eliminate interference, strain gauges are attached to the upper and lower surfaces of both the first and second crossbeams 11 and 13. The strain gauges are arranged axially along the beam segment and form a Wheatstone full-bridge circuit. Each full-bridge circuit consists of four strain gauges. The strain gauges in adjacent bridge arms experience opposite bending strains, which not only doubles the output voltage but also effectively eliminates zero-point drift caused by changes in ambient temperature, achieving temperature compensation and common-mode interference cancellation.

[0071] The strain gauges used are either resistance strain gauges or silicon-based MEMS piezoresistive strain gauges. Resistance strain gauges are suitable for general precision measurement applications, while silicon-based MEMS piezoresistive strain gauges offer higher sensitivity and are suitable for precise detection of minute strains. Furthermore, this structure only requires the gauges to be attached to the upper and lower surfaces of the first crossbeam 11 and the second crossbeam 13, eliminating the need for side attachments, thus adapting to automated production requirements. In addition, the force-bearing end of the first crossbeam 11 is connected to the loading platform 3, and the connecting end of the second crossbeam 13 is connected to the fixed end 2, forming a stable force transmission path.

[0072] Measurement of vertical force Fz and torque Mz: The vertical force Fz and torque Mz are detected by strain gauges on the upper and lower surfaces of the first crossbeam 11 and the second crossbeam 13. The formula for measuring the vertical force Fz is as follows: The formula for measuring torque Mz is: . The equivalent strain of the entire bridge corresponding to the vertical force Fz is... The full-bridge equivalent strain corresponding to torque Mz is obtained by calibration and conversion of the output voltage of the corresponding Wheatstone full-bridge circuit.

[0073] Horizontal forces Fx and Fy are measured by bending deformation of the corresponding horizontally arranged beam segments, the first crossbeam 11 and the second crossbeam 13. When the external horizontal force Fx or Fy acts on the loading platform 3, the force is transmitted through the first crossbeam 11 to the connecting beam 12, and a bending moment M = F·H is formed through the connecting beam 12, where H is the height of the connecting beam 12, i.e., the vertical distance between the upper and lower end faces of the connecting beam 12, which constitutes the lever arm of the horizontal force on the neutral layer of the second crossbeam 13. The formula for measuring the horizontal force Fx or Fy is: , ,in , These are the equivalent strains of the full bridge corresponding to horizontal forces Fx and Fy, respectively. When Fx is applied, the two sets of elastic beam structures symmetrically arranged in the X direction produce opposite bending strains. The signals collected by the strain gauges are connected to the same full bridge to achieve differential output, thereby improving measurement accuracy.

[0074] The overturning moments Mx and My are measured by asymmetric bending strain of the corresponding horizontally arranged beam segments, first beam 11 or second beam 13. The measurement formula is as follows: , ,in , These are the full-bridge equivalent strains corresponding to the overturning moments Mx and My, respectively. For example, when an overturning moment Mx is applied, the two sets of elastic beams in the Y direction will produce opposite bending deformations, one in tension and one in compression. The reverse strain signals collected by the strain gauges are extracted through a differential bridge circuit to obtain the relevant data of the overturning moment Mx. The measurement logic of My is the same as that of Mx.

[0075] Decoupling between the six-dimensional force and the equivalent strain of each bridge circuit is achieved through decoupling matrices, which are divided into diagonal matrices and fully coupled matrices. Under ideal machining and symmetrical assembly conditions, there is no theoretical coupling between the forces / torques in each dimension, and the signal conversion can be directly performed using a diagonal matrix to ensure the accuracy of the measurement results. In practical engineering applications, due to factors such as machining tolerances, patch position deviations, and load eccentricity, there will be slight cross-coupling between the dimensions. In this case, a 6×6 fully coupled decoupling matrix needs to be obtained through standard static calibration tests. Dimensional crosstalk is then eliminated through software calculations to further improve the measurement accuracy of the sensor.

[0076] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A non-linear elastic beam structure, characterized in that, The elastic beam structure is non-linear, and at least two spaced strain detection zones are provided on the elastic beam structure. When the elastic beam structure is subjected to external force, at least part of the axial force or lateral force applied to it will be converted into bending moment acting on the strain detection area. The strain detection zone is used to detect the strain generated by the bending moment and / or the directly applied tensile and compressive loads.

2. The non-linear elastic beam structure according to claim 1, characterized in that, The structure includes an L-shaped non-linear elastic beam structure formed by an L-shaped arrangement of a first crossbeam (11) and a connecting beam (12). Both the first crossbeam (11) and the connecting beam (12) are of equal cross-section. The ends of the first crossbeam (11) and the connecting beam (12) that are far apart are the force-bearing end and the connection end, respectively. A fixed angle is formed between the first crossbeam (11) and the connecting beam (12). When a concentrated force F and a moment M are applied to the stressed end, a bending moment Mh is generated on the connecting beam (12), and a moment Ml is generated at the first crossbeam (11). The bending moment Mh satisfies the following relationship: Mh = M + F × h × sinθ, where h is the length from the stressed end to the center of the patch on the connecting beam (12), and θ is the angle between the first crossbeam (11) and the connecting beam (12). The moment Ml satisfies the following relationship: Ml = M + F × L × sinθ, where L is the axial distance from the stressed end to the first crossbeam (11). The following can be calculated respectively: F=(Ml-Mh) / [(Lh)sinθ], M=(Ml+Mh-F(L+h)sinθ) / 2.

3. The non-linear elastic beam structure according to claim 1, characterized in that, The non-linear elastic beam structure is an arc-shaped structure. Strain gauges are installed at both ends of the arc-shaped structure to form a half-bridge. When a concentrated force F and a moment M are applied to the stressed end, a bending moment Mh and a moment Ml are generated at both ends of the arc-shaped structure. The bending moment Mh satisfies the relationship: Mh = M + F × h × sinθ, where h is the length from the stressed end to the center of the strain gauge near the stressed end, and θ is the angle between the center lines of the strain gauges at both ends of the arc-shaped structure. The moment Ml satisfies the relationship Ml = M + F × L × sinθ, where L is the axial distance from the stressed end to the strain gauge away from the center of the strain gauge. These can be calculated as follows: F=(Ml-Mh) / [(Lh)sinθ], M=(Ml+Mh-F(L+h)sinθ) / 2.

4. A non-linear elastic beam structure according to claim 2, characterized in that, It also includes a second crossbeam (13) fixedly connected to the end of the connecting beam (12) away from the first crossbeam (11). The first crossbeam (11), the connecting beam (12) and the second crossbeam (13) are all of equal cross-section structure, forming a Z-shaped non-linear elastic beam structure. When force F and torque M are applied to the force-bearing end, the force Ml at the first crossbeam (11) satisfies the relationship Ml=M+F×L×sinθ, where L is the distance from the force-bearing end to the axial direction of the first crossbeam (11), and the force at the second crossbeam (13) is M. Solve for F=(Ml-M) / (Lsinθ). The first crossbeam (11) and the second crossbeam (13) are arranged in parallel, with the first crossbeam (11) and the second crossbeam (13) being respectively the force-bearing end and the connection end at opposite ends.

5. A six-dimensional force sensor employing the non-linear elastic beam structure described in claim 2, 3, or 4, comprising a fixed end (2), a loading stage (3), and an elastic body (1), characterized in that, The elastic body (1) is composed of at least three sets of non-linear elastic beam structures. Each set of non-linear elastic beam structures is arranged in a ring array around the center of the loading platform (3). The connecting end of each set of non-linear elastic beam structures is connected to the fixed end (2). The force-bearing end of each set of non-linear elastic beam structures is connected to the loading platform (3). Strain gauges (4) are provided on the surfaces of the first crossbeam (11) and the second crossbeam (13). Strain gauges are installed on the side of the connecting beam (12) of the L-shaped elastic beam structure.

6. The six-dimensional force sensor employing a non-linear elastic beam structure according to claim 5, characterized in that, The strain gauges on the upper and lower surfaces of the first crossbeam (11) and the second crossbeam (13) are used to measure the vertical force Fz. The upper and lower surfaces of the first crossbeam (11) or the second crossbeam (13) are provided with strain gauges at 45° and 135° to the axial direction of the beam segment, respectively, to measure the torque Mz. The formula for measuring vertical force Fz is: , The formula for measuring torque Mz is: , Where E is the modulus of elasticity, I is the moment of inertia of the beam segment section, L is the effective bending length of the beam segment, and y is the distance from the patch to the neutral layer. The equivalent strain of the entire bridge corresponding to the vertical force. This represents the equivalent strain of the entire bridge corresponding to the torque.

7. The six-dimensional force sensor employing a non-linear elastic beam structure according to claim 6, characterized in that, The horizontal forces Fx and Fy are measured by bending deformation of the corresponding horizontally arranged beam segments. The horizontal forces Fx or Fy are transmitted through the connecting beam (12) to form a bending moment M=F·H, where H is the height of the connecting beam (12). The formula for measuring horizontal force Fx or Fy is: ， ， in , These are the equivalent strains of the full bridge corresponding to horizontal forces Fx and Fy, respectively.

8. The six-dimensional force sensor employing a non-linear elastic beam structure according to claim 7, characterized in that, The overturning moments Mx and My are measured by asymmetric bending strain of the corresponding horizontally arranged beam segments, and the measurement formula is as follows: ， ， in , These are the full-bridge equivalent strains corresponding to the overturning moments Mx and My, respectively.

9. The six-dimensional force sensor employing a non-linear elastic beam structure according to claim 8, characterized in that, The strain gauges are arranged axially along the beam segment and form a Wheatstone full-bridge circuit for temperature compensation and interference cancellation.

10. The six-dimensional force sensor employing a non-linear elastic beam structure according to claim 9, characterized in that, The decoupling matrix between the six-dimensional force and the equivalent strain of each bridge circuit is either a diagonal matrix or a fully coupled matrix. Where the coefficients are: .

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