Combined decoupling type three-axis force sensor

Abstract

The application discloses a combined decoupling type three-axis force sensor, which comprises a ring type fixing table, a force loading table, a first force measuring module, a second force measuring module, a third force measuring module, a threaded fastener and a strain gauge attached thereon. The first force measuring module is composed of two symmetric elastic force sensitive branches and a special-shaped connecting block in parallel, the second force measuring module is arranged on the special-shaped connecting block and comprises two pairs of symmetric non-equal-length elastic thin beams and square guide blocks, and the third force measuring module is a double-hole structure with threaded through holes at two ends. The first force measuring module, the second force measuring module and the ring type fixing table are integrally formed, the outer end planes of the three force measuring modules are respectively used for attaching and arranging strain gauges to form three full-bridge circuits, and each group is responsible for measuring one-dimensional axial force. The combined configuration can realize three-dimensional space three orthogonal axial force component decoupling and effectively suppress the output signal coupling crosstalk problem among the axial forces from the structure, is convenient for sheet arrangement and bridge formation, simplifies the calibration process, effectively reduces the decoupling algorithm difficulty, improves the sensor linearity and sensitivity, and is suitable for the demand for three-axis force information rapid response and accurate measurement in industrial robots, high-end manufacturing equipment, intelligent logistics and modern agriculture and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a triaxial force sensor, in particular to a combined decoupling type triaxial force sensor. BACKGROUND

[0002] The triaxial force sensor can be used to sense the three orthogonal axis force information with changing direction and size in three-dimensional space at the same time, which is a very important type of sensor, widely used in industrial robots, high-end machine tools, wind tunnel balances and intelligent manufacturing and many other fields, providing force sense information for environmental interaction of mechanical devices or robots.

[0003] The existing triaxial force sensor configuration is less, and has the problems of difficult processing, difficult patching of bridge, serious inter-axis coupling and the like. Patent CN116124349A proposes a three-dimensional force sensor based on three force measurement modules to measure branch parallel, which is used to detect two-dimensional orthogonal axis force and one-dimensional plane normal torque. The "X" type variable cross-section beam unit is connected in series at both ends of the elastic measurement body in the force measurement module to effectively solve the problems of stress concentration and center offset of force and displacement transmission beam. However, the sensor has coupling problems between the three-dimensional load and the force measurement module, which affects the measurement accuracy. Patent CN102519635B discloses a triaxial force sensor with overload protection function, which surrounds the sensor elastic body on the base by the overload protection shell, limits the deformation of the elastic element to prevent its overload damage, and measures the three-axis force of the sensor through the same direction series connection of each axis force structure, which results in the overall thickness of the sensor being too large, thereby increasing the load torque of the driving mechanism. Patent CN103292939B discloses a spoke and center pin column combined type three-dimensional force sensor, which uses the paste on the cross-shaped elastic body and the four block string to realize the measurement of three orthogonal axis forces, wherein the three-axis force measurement utilizes shear strain, resulting in low sensitivity of the sensor in small range force measurement scene, and the series arrangement of each force measurement module makes the overall height of the sensor not easy to control.

[0004] In view of the deficiencies of the prior art, it is urgent to develop a triaxial force sensor with the advantages of small structure, easy patching and bridge arrangement, easy molding and manufacturing, high linearity, high sensitivity and inter-axis decoupling for pure axial force measurement, so as to effectively meet the application requirements of high-precision high-speed high-dynamic response triaxial force sensor in the fields of intelligent equipment and industrial automation. SUMMARY

[0005] The purpose of the present application is to solve the problems of complex sensor structure, high and difficult to control, difficult to patch and inter-axis coupling between three-axis forces in the prior art, and to propose a combined decoupling type triaxial force sensor.

[0006] In order to achieve the above object, the technical scheme of the present application is as follows: a combined decoupling three-axis force sensor, characterized in that the sensor comprises a combined elastic structure and a plurality of strain gauges (10). The combined elastic structure comprises a ring-shaped fixed platform (1), a U-shaped notch cylindrical force loading platform (2), a first force measuring module connected with the ring-shaped fixed platform (1), a second force measuring module located in a special-shaped connecting block (5), and a third force measuring module fixedly connecting the second force measuring module and the force loading platform (2), wherein the ring-shaped fixed platform (1), the third force measuring module and the force loading platform (2) are left-right symmetrical in the length direction and the symmetry planes of the three are coplanar.

[0007] Preferably, the ring-shaped fixed platform (1), the first force measuring module and the second force measuring module are integrally formed.

[0008] Preferably, the ring-shaped fixed platform (1) adopts a cylindrical hollow structure, comprising an irregular structure (110) and a square block (120) according to the inner shape structure of the first force measuring module, wherein a gap is left between the inner ring of the irregular structure (110) and the outer ring of the force loading platform (2), four square symmetrical fixed counterbores (130) are arranged around the gap, and the fixed counterbores (130) are collinear with the center of the outer cylindrical surface at the positions.

[0009] Preferably, the first force measuring module is formed by two symmetrical elastic force sensitive branch chains (3) arranged along the length direction, and the square block (120) and the special-shaped connecting block (5) are fixedly connected at the head and tail of the two elastic force sensitive branch chains (3), the elastic force sensitive branch chain (3) is composed of a variable cross-section beam (4) connected in series at the head and tail, the outer side planes of the two notches are symmetrically arranged with strain gauges (10) at the thinnest positions, the inner side planes are cylindrical surfaces and gaps are left between the inner side planes and the outer cylindrical surface of the fixed counterbores (130), and the special-shaped connecting block (5) is obtained by symmetrically cutting L-shaped notches (53) from the rectangular block (51) along the length direction symmetry center plane (11).

[0010] Preferably, the second force measuring module is located in the special-shaped connecting block (5) and comprises two pairs of symmetrical non-equal-length elastic thin beams (6) and square guide blocks (7), the special-shaped block (52) and the square guide block (7) are connected in parallel through the elastic thin beams (6), the elastic thin beams (6) are solid structures and the cross-sectional shape remains unchanged along the length direction, the shorter elastic thin beams (6) are located on the inner side of the second force measuring module, the longer elastic thin beams (6) are located on the outer side of the second force measuring module, and strain gauges (10) are arranged on the outer surface of the longer elastic thin beams (6) along the thickness direction symmetry line, the square guide block (7) is provided with a square through hole (71) at the thickness direction symmetry position, and columnar counterbores (72) are arranged on the upper and lower surfaces of the square guide block (7) along the length direction symmetry center line.

[0011] Preferably, the third force measuring module is a double-hole structure (9) with threaded holes (91) at both ends, the threaded holes (91) are arranged on the symmetric center line along the width direction, the double-hole through slot (92) is arranged on the left and right sides along the thickness direction and is symmetric about the thickness direction symmetric center surface (11), and the outer side planes of the four thinnest corners of the double-hole through slot (92) are symmetrically arranged with strain gauges (10).

[0012] Preferably, the cylindrical force loading platform (2) is provided with a U-shaped notch (21), a square slot (22) is arranged at the symmetric position along the thickness direction, the top surface of the force loading platform (2) is provided with a plurality of square threaded connection holes (23) arranged in a square shape and a straight line arranged counterbore (24), and the center line of the counterbore (24) is located on the symmetric surface (11) of the U-shaped notch (21) of the force loading platform (2).

[0013] Preferably, the elastic force sensitive branch chain (3), the longer elastic thin beam (6) and the double-hole structure (9) are all sunk by a certain thickness at the positions of the outer surfaces arranged with strain gauges (10), so as to facilitate dustproof sealing of the strain gauges (10) and bridge lines by using silicone rubber, and the two sides of the outer surface are transitioned by using a circular arc.

[0014] Preferably, the third force measuring module penetrates the square through hole (71) of the square guide block (7) and the square slot (22) of the cylindrical force loading platform (2) at the head and tail respectively, and is combined and fastened by a threaded fastener (8).

[0015] Preferably, the strain gauges (10) are twelve, which are arranged at the positions of the outer planes of the first force measuring module, the second force measuring module and the third force measuring module respectively, and together form three sets of Wheatstone full-bridge circuits, each set is responsible for measuring one-dimensional axial force.

[0016] The combined decoupling type three-axis force sensor has the advantages that three-dimensional space three orthogonal axial force components can be decoupled and the output signal coupling crosstalk problem among the axial forces can be effectively inhibited, the strain gauges can be easily arranged and the bridge circuits can be easily formed, the calibration process is simplified, the decoupling algorithm difficulty is effectively reduced, the sensor linearity and sensitivity are improved, the sensor is suitable for the needs of rapid response and accurate measurement of three-axis force information in industrial robots, high-end manufacturing equipment, intelligent logistics and modern agriculture and the like. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed in the embodiments will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained based on these drawings.

[0018] Figure 1 A structural schematic diagram of a combined three-dimensional force sensor provided by the embodiment of the present application is shown in the figure.

[0019] Figure 2 A schematic diagram of a ring-shaped fixing table provided by the embodiment of the present application is shown in the figure.

[0020] Figure 3 A schematic diagram of a first force measuring module provided by the embodiment of the present application is shown in the figure.

[0021] Figure 4 A schematic diagram of a second force measuring module provided by the embodiment of the present application is shown in the figure.

[0022] Figure 5 A schematic diagram of a third force measuring module provided by the embodiment of the present application is shown in the figure.

[0023] Figure 6 A schematic diagram of a cylindrical force loading table provided by the embodiment of the present application is shown in the figure.

[0024] Figure 7 A schematic diagram of path 1-6 is shown in the figure.

[0025] Figure 8 A schematic diagram of a positive elastic strain on path 1 when Fx=70N is applied is shown in the figure.

[0026] Figure 9 A schematic diagram of a positive elastic strain on path 2 when Fx=70N is applied is shown in the figure.

[0027] Figure 10 A schematic diagram of a positive elastic strain on path 3 when Fx=70N is applied is shown in the figure.

[0028] Figure 11 A schematic diagram of a positive elastic strain on path 4 when Fx=70N is applied is shown in the figure.

[0029] Figure 12 A schematic diagram of a positive elastic strain on path 5 when Fx=70N is applied is shown in the figure.

[0030] Figure 13 A schematic diagram of a positive elastic strain on path 6 when Fx=70N is applied is shown in the figure.

[0031] 1. Ring-shaped fixed platform; 110. Irregular structure; 120. Square block; 130. Fixed countersunk hole; 2. Force loading platform; 21. U-shaped notch; 22. Square groove; 23. Threaded connection hole; 24. Countersunk hole; 3. Elastic force-sensitive branch; 4. Variable cross-section beam; 5. Irregular connecting block; 51. Rectangular block; 52. Irregular block; 53. L-shaped groove; 6. Elastic thin beam; 7. Square guide block; 71. Square through hole; 72. Columnar countersunk hole; 8. Threaded fastener; 9. Double hole structure; 91. Threaded through hole; 92. Double hole through groove; 10. Strain gauge; 11. Symmetry center plane. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0033] like Figures 1-3 As shown, a combined decoupled triaxial force sensor is characterized in that: the sensor includes a combined elastic structure and several strain gauges (10). The combined elastic structure includes a ring-shaped fixed platform (1), a cylindrical force loading platform (2) with a U-shaped notch, a first force measuring module connected to the ring-shaped fixed platform (1), a second force measuring module located in the irregular connecting block (5), and a third force measuring module fixedly connected to the second force measuring module and the force loading platform (2). The ring-shaped fixed platform (1), the third force measuring module and the force loading platform (2) are symmetrical in the length direction and their symmetrical planes are coplanar.

[0034] The ring-shaped fixed platform (1), the first force measuring module, and the second force measuring module are integrally formed.

[0035] The ring-shaped fixed platform (1) adopts a cylindrical hollow structure, including an irregular structure (110) and a square block (120) designed according to the internal shape of the first force measuring module. There is a gap between the inner ring of the irregular structure (110) and the outer ring of the force loading platform (2). Four square countersunk holes (130) are arranged symmetrically around it. The countersunk holes (130) are collinear with the center of the outer cylindrical surface of the platform.

[0036] The first force module is formed by two elastic force sensitive branch chains (3) arranged symmetrically along the length direction, and the square block (120) and the special-shaped connecting block (5) are fixed in parallel at the head and tail of the elastic force sensitive branch chains (3). The elastic force sensitive branch chain (3) is composed of variable cross-section beams (4) in series at the head and tail. The outer side planes of the two notches at the thinnest part are symmetrically arranged with strain gauges (10). The inner side is a cylindrical surface and has a gap with the outer cylindrical surface of the fixed counterbore (130). The special-shaped connecting block (5) is obtained by symmetrically cutting L-shaped notches (53) on both sides of the length direction symmetry center surface (11) of the rectangular block (51).

[0037] The second force module is located in the special-shaped connecting block (5) and includes two pairs of symmetric non-equal-length elastic thin beams (6) and square guide blocks (7). The special-shaped block (52) and the square guide block (7) are connected in parallel through the elastic thin beam (6). The elastic thin beam (6) is of solid structure and the cross-sectional shape remains unchanged along the length direction. The shorter elastic thin beam (6) is located on the inner side of the second force module, and the longer elastic thin beam (6) is located on the outer side of the second force module. Strain gauges (10) are arranged on the outer surface of the longer elastic thin beam (6) along the thickness direction symmetry line. The square guide block (7) is provided with a square through hole (71) at the thickness direction symmetry position, and the upper and lower surfaces are provided with cylindrical counterbores (72) along the length direction symmetry center line.

[0038] The third force module is a double-hole structure (9) with threaded through holes (91) at both ends. The threaded through holes (91) are arranged on the symmetry center line along the width direction. The double-hole through slot (92) is arranged on the left and right side surfaces along the thickness direction and is symmetric about the thickness direction symmetry center surface (11). Strain gauges (10) are symmetrically arranged on the outer side planes of the four notches at the thinnest part of the double-hole through slot (92).

[0039] The cylindrical force loading platform (2) is provided with a U-shaped notch (21) and a square slot (22) at the thickness direction symmetry position. The top surface of the force loading platform (2) is provided with a plurality of square arranged threaded connection holes (23) and straight arranged counterbores (24), and the counterbores (24) are arranged on the symmetry surface (11) of the U-shaped notch (21).

[0040] The outer surface positions of the elastic force sensitive branch chain (3), the longer elastic thin beam (6) and the double-hole structure (9) for arranging the strain gauges (10) are all sunken by a certain thickness, which facilitates the use of silicone rubber to dustproof and seal the strain gauges (10) and the bridge circuit. The outer surface of both sides adopts a circular arc transition.

[0041] The third force module penetrates the square through hole (71) of the square guide block (7) and the square slot (22) of the cylindrical force loading platform (2) at the head and tail respectively, and forms a combined fastening connection through a threaded fastener (8).

[0042] The strain gauges (10) are twelve, respectively arranged at the first force measuring module outer plane, the second force measuring module outer plane and the third force measuring module outer plane positions, and together constitute three groups of Wheatstone full bridge circuits, each group is responsible for measuring one-dimensional axial force.

[0043] The embodiment and the drawing only list a strain gauge pasting position and a method for decoupling of the first force measuring module, and the strain gauge pasting position and the bridge forming method can also be selected according to the actual needs of decoupling, and all belong to the protection scope of the patent.

[0044] Referring to Figures 7-13 : In order to analyze the decoupling characteristics of the three-axis force sensor of the embodiment by ANSYS software, a space coordinate system is established at the geometric center of the force loading table, the OY axis and the OZ axis are located on the symmetry center plane (11) and the OZ axis is perpendicular to the top surface of the force loading table (2), Figure 7 is a schematic diagram of paths 1-6, paths 1 and 2 are parallel to the OZ axis, used to identify and solve the positive elastic strain at the pasting position of the first force measuring module, paths 3 and 4 are parallel to the OX axis, used to solve the inter-dimension coupling degree of the first force measuring module to the second measuring module, and paths 5 and 6 are perpendicular to the OY axis, used to solve the inter-dimension coupling degree of the first force measuring module to the third measuring module. Figures 8-13 In turn, the first measuring module perceives the load, that is, the load of 70N is applied to the threaded connection hole (23) of the force loading table (2) along the X axis direction, and the positive elastic strain of the six paths along the defined path direction is shown in the schematic diagram, the horizontal coordinate is the path length, and the vertical coordinate is the positive elastic strain value on the path, wherein 1με=10 -6 mm / mm.

[0045] The first force measuring module, the second force measuring module and the third force measuring module each define two paths, two strain gauges (10) are arranged on each path, and four strain gauges (10) constitute three groups of Wheatstone full bridge circuits. When the designed decoupling type three-axis force sensor is applied to the threaded connection hole (23) of the force loading table (2) along the X axis direction with a load of 70N, the positive elastic strain of the two paths on the first force measuring module for measuring the force in the direction is shown in Figure 8 and 9 The average positive elastic strain value at the identified strain gauge (10) pasting position is obtained, and the bridge output strain is about 550με. The non-desired positive elastic strain of the two paths on the second measuring module of the non-X axis force measuring bridge under the action of the load of 70N in the X axis direction is shown in Figure 10 and 11As shown, the average positive elastic strain value at the identified strain gauge (10) layout position is calculated to obtain an unexpected bridge output strain less than 0.140με, so the inter-dimension coupling of the first measurement module to the second measurement module can be obtained as 0.140με / 550με=0.025%F.S. The unexpected positive elastic strain of the two paths of the non-X axial force measurement bridge on the third measurement module under the action of a load of 70N in the X axis direction is as shown in FIG. 6B. Figure 12 and 13 As shown, the average positive elastic strain value at the identified strain gauge (10) layout position is calculated to obtain an unexpected bridge output strain less than 0.144με, so the inter-dimension coupling of the first measurement module to the third measurement module can be obtained as 0.144με / 550με=0.025%F.S. Through the analysis of the above embodiments, it can be seen that the designed three-axial force sensor can effectively suppress the coupling crosstalk of the output signals between the axial forces.

[0046] The above merely describes certain exemplary embodiments of the present application in a descriptive manner, and it is needless to say that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present application. Therefore, the above drawings and descriptions are illustrative in nature and should not be understood as limiting the scope of protection of the claims of the present application.

[0047] The above is a specific description of the technical idea of the present application, but cannot limit the protection scope of the present application, and any equivalent implementation or modification without departing from the present application should be included in the patent scope of the present application.

Claims

1. A combined decoupled triaxial force sensor, characterized in that: The sensor includes a combined elastic structure and several strain gauges; the combined elastic structure includes a ring-shaped fixed platform, a cylindrical force loading platform with a U-shaped notch, a first force measuring module connected to the ring-shaped fixed platform, a second force measuring module located in the irregular connecting block, and a third force measuring module fixedly connected to the second force measuring module and the force loading platform. The ring-shaped fixed platform, the third force measuring module and the force loading platform are symmetrical in the length direction and their symmetrical planes are coplanar.

2. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The encircling fixed platform, the first force measuring module, and the second force measuring module are integrally formed.

3. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The ring-shaped fixing platform adopts a cylindrical hollow structure, including an irregular structure and a square block designed according to the internal shape of the first force measuring module. There is a gap between the inner ring of the irregular structure and the outer ring of the force loading platform. Four square countersunk holes are provided around it, and the center of the countersunk holes is collinear with the center of the outer cylindrical surface at its location.

4. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The first force measuring module is composed of two symmetrically arranged elastic force-sensitive branches connected end to end in a square block and an irregular connecting block. The elastic force-sensitive branches are composed of variable cross-section beams connected end to end. Strain gauges are symmetrically arranged on the outer plane of the thinnest part of the two slots. The inner surface of the branch is a cylindrical surface and a gap is left between it and the outer cylindrical surface of the fixed counterbore. The irregular connecting block is obtained by symmetrically cutting L-shaped slots on both sides of the symmetrical center plane of the rectangular block along the length direction.

5. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The second force measuring module is located inside the irregular connecting block and includes two pairs of symmetrical non-equal length elastic thin beams and square guide blocks. The irregular block and the square guide blocks are connected in parallel through the elastic thin beams. The elastic thin beams are solid structures and their cross-sectional shape remains unchanged along their length direction. The shorter elastic thin beam is located inside the second force measuring module, and the longer elastic thin beam is located outside the second force measuring module. Strain gauges are arranged on the outer surface of the elastic thin beams along the symmetrical line of the thickness direction. The square guide blocks have square through holes at symmetrical positions along the thickness direction, and cylindrical countersunk holes are provided on the upper and lower surfaces along the symmetrical center line of the length direction.

6. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The third force measuring module is a double-hole structure with threaded through holes at both ends. The threaded through holes are all located on the symmetrical center line along the width direction. The double-hole through grooves are located on the left and right sides along the thickness direction and are symmetrical about the symmetrical center plane of the thickness direction. Strain gauges are symmetrically arranged on the outer plane of the thinnest part of the four slots of the double-hole through grooves.

7. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The cylindrical force loading platform has a U-shaped notch and a square groove symmetrically positioned along its thickness direction. It has several threaded connection holes arranged in a square and countersunk holes arranged in a straight line on its upper and lower surfaces, and the rotation center line of the countersunk holes is located on the symmetrical surface of its U-shaped notch.

8. The combined decoupled triaxial force sensor according to claim 4, characterized in that: The elastic force-sensitive branch used for mounting strain gauges has its outer surface recessed by a certain thickness to facilitate the use of silicone rubber to seal the strain gauges and bridge circuits for dust prevention. The outer surface has rounded transitions on both sides.

9. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The third force measuring module passes through the square through hole of the square guide block and the square groove of the cylindrical force loading platform at both ends, and forms a combined fastening connection through threaded fasteners.

10. The combined decoupled triaxial force sensor according to claim 1, characterized in that: The strain gauges consist of twelve units, which are respectively arranged on the outer planes of the first, second, and third force measuring modules, forming three sets of Wheatstone full-bridge circuits. Each set is responsible for measuring one-dimensional axial force.

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