A three-dimensional force sensor and a robotic arm

Abstract

The present invention provides a three-dimensional force sensor and a robotic arm. The three-dimensional force sensor includes two main structures arranged vertically, two first strain beams, and a third strain beam. Each main structure includes two oppositely arranged first side surfaces and two oppositely arranged second side surfaces, the first and second side surfaces being perpendicular to each other. Each first side surface is provided with a fixing block having at least one first positioning hole. Each second side surface is provided with a second strain beam. Each first strain beam is arranged perpendicularly between two second strain beams of the same main structure. The third strain beam is arranged perpendicularly between two first strain beams. Strain gauges are provided on each of the first, second, and third strain beams. By arranging strain beams in three mutually perpendicular directions, the three-dimensional force sensor of the above scheme can reduce inter-dimensional coupling and improve the measurement accuracy of the sensor.

Description

Technical Field

[0001] The present invention relates to the field of micro-vibration measurement, and in particular to a three-dimensional force sensor and a mechanical arm. Background Art

[0002] As robotic arms play an increasingly important role in the rapid development of industrial automation, sensors, as the basis for robotic arms to perceive the outside world, are also receiving more attention and attention.

[0003] Since the 1970s, multi-dimensional force sensors for robotic arms have become a global research hotspot, with significant implications for their research and application. Three-dimensional force sensors can measure forces in three directions within a spatial coordinate system. They can be applied to the end of a robotic arm to sense the forces acting on the object being manipulated and achieve adaptive force control.

[0004] As we all know, multi-dimensional force sensors are sensitive to forces in all directions. This means that force in one dimension can cause output in other dimensions, leading to interdimensional coupling between the input and output. This can, to a certain extent, cause errors in the sensor's measurement process. Therefore, reducing interdimensional coupling is key to improving sensor measurement accuracy.

[0005] In the existing technology, a cross-beam structure is generally used to achieve multi-dimensional force measurement through two layers of floating beams inside and outside and strain gauges. In the measurement of large forces and small moments, an eight-beam structure is also designed to improve its strength. However, in a precise experimental environment, the end of the robotic arm is required to sense tiny force changes, which requires the sensor to have high sensitivity. Although the above traditional sensors have good strength, they still cannot meet certain requirements in terms of sensitivity.

[0006] Therefore, how to reduce the inter-dimensional coupling of a three-dimensional force sensor and improve its sensitivity is a problem that people in this field currently need to solve. Summary of the Invention

[0007] In order to overcome the above-mentioned defects in the prior art, the present invention proposes a three-dimensional force sensor and a robotic arm. The three-dimensional force sensor has low inter-dimensional coupling and high sensitivity, which can greatly reduce measurement errors and improve measurement reliability. It can be used at the end of aerospace robotic arms and other occasions with high requirements for force control and measurement accuracy.

[0008] To achieve the above objectives, the present invention provides the following specific technical solutions:

[0009] In a first aspect, the present invention provides a three-dimensional force sensor comprising:

[0010] Two main body structures are arranged above and below, each main body structure includes two first side surfaces and two second side surfaces arranged opposite to each other, the first side surfaces and the second side surfaces are perpendicular to each other, each first side surface is provided with a fixing block, and the fixing block is provided with at least one first positioning hole; each second side surface is provided with a second strain beam;

[0011] Two first strain beams, each first strain beam is vertically arranged between two second strain beams of the same main body structure;

[0012] a third strain beam, vertically arranged between the two first strain beams;

[0013] Strain gauges are provided on the first strain beam, the second strain beam and the third strain beam.

[0014] As an optional embodiment, the method further includes:

[0015] The loading block is sleeved on the third strain beam, and is provided with at least one second positioning hole.

[0016] As an optional embodiment, there are multiple second positioning holes, which are evenly distributed on the surface of the loading block.

[0017] As an optional embodiment, the strain gauges provided on the third strain beam are third strain gauges, the number of the third strain gauges is 2n, where n is a positive integer greater than 1; the third strain gauges are arranged in groups of two on both sides of the third strain beam; and every four third strain gauges constitute a full-bridge circuit.

[0018] As an optional embodiment, the strain gauge provided on the first strain beam is a first strain gauge, and the number of first strain gauges provided on each first strain beam is two, and the two first strain gauges are provided on the top surface or the bottom surface of the first strain beam; every four first strain gauges constitute a full-bridge circuit.

[0019] As an optional embodiment, at least two second strain beams are provided with second strain gauges, the number of second strain gauges provided on each second strain beam is two, and the two second strain gauges are provided on the outer side surfaces of the second strain beam; every four second strain gauges constitute a full-bridge circuit.

[0020] As an optional embodiment, the first strain beam, the second strain beam and the third strain beam are in the shape of thin plates.

[0021] As an optional embodiment, the first side surface and the second side surface are integrally formed; the second side surface is a plane where the second strain beam is located along the length direction.

[0022] As an optional embodiment, the first strain beam is fixedly connected to the main body structure, and the first strain beam and the third strain beam are detachably connected or integrally formed;

[0023] The third strain beam is connected to the center positions of the two first strain beams, and the first strain beam is connected to the center positions of the two second strain beams on the same main body structure.

[0024] In a second aspect, the present invention further provides a robotic arm comprising:

[0025] The robot arm body is provided with at least one third positioning hole;

[0026] The three-dimensional force sensor is the three-dimensional force sensor of the first aspect of the present invention. The three-dimensional force sensor is detachably arranged at the end of the robotic arm body, and the second positioning hole and the third positioning hole are fixed by a locking piece.

[0027] The present invention can achieve the following technical effects:

[0028] The present invention provides a three-dimensional force sensor and a robotic arm. The three-dimensional force sensor includes two main structures arranged vertically, two first strain beams, and a third strain beam. Each main structure includes two oppositely arranged first side surfaces and two oppositely arranged second side surfaces, the first and second side surfaces being perpendicular to each other. Each first side surface is provided with a fixing block having at least one first positioning hole. Each second side surface is provided with a second strain beam. Each first strain beam is arranged perpendicularly between two second strain beams of the same main structure. The third strain beam is arranged perpendicularly between two first strain beams. Strain gauges are provided on each of the first, second, and third strain beams. By arranging strain beams in three mutually perpendicular directions, the three-dimensional force sensor of the above scheme can reduce inter-dimensional coupling and improve the measurement accuracy of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of a three-dimensional force sensor according to an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the distribution of strain gauges on a three-dimensional force sensor according to an embodiment of the present application;

[0031] Figure 3 Schematic diagram of a Wheatstone full-bridge circuit consisting of four strain gauges according to an embodiment of the present application;

[0032] Figure 4 This is a finite element analysis diagram of a three-dimensional force sensor provided by an embodiment of the present application subjected to a force in a first direction;

[0033] Figure 5 This is a finite element analysis diagram of a three-dimensional force sensor provided by an embodiment of the present application subjected to a force in a second direction;

[0034] Figure 6 This is a finite element analysis diagram of a three-dimensional force sensor provided by one embodiment of the present application subjected to a force in a third direction.

[0035] Reference numerals:

[0036] 1. Fixed block;

[0037] 11. First positioning hole;

[0038] 2. Load the block;

[0039] 21. Second positioning hole;

[0040] 3. Second strain beam;

[0041] 4. The first strain beam;

[0042] 5. The third strain beam;

[0043] 6. Strain gauge;

[0044] 61. First strain gauge a;

[0045] 62. First strain gauge b;

[0046] 63. First strain gauge c;

[0047] 64, first strain gauge d;

[0048] 65. Second strain gauge a;

[0049] 66. Second strain gauge b;

[0050] 67. Second strain gauge c;

[0051] 68. Second strain gauge d;

[0052] 69. The third strain gauge a;

[0053] 610, third strain gauge b;

[0054] 611, third strain gauge c;

[0055] 612. The third strain gauge d. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0057] like Figure 1As shown, in a first aspect, the present invention provides a three-dimensional force sensor, comprising two main body structures arranged one above the other, two first strain beams and a third strain beam;

[0058] Each main body structure includes two oppositely arranged first side surfaces and two oppositely arranged second side surfaces, the first side surfaces and the second side surfaces being perpendicular to each other, a fixing block 1 being provided on each first side surface, and at least one first positioning hole 11 being provided on the fixing block 1; a second strain beam 3 being provided on each second side surface; each first strain beam 4 being perpendicularly arranged between two second strain beams 3 of the same main body structure; a third strain beam 5 being perpendicularly arranged between two first strain beams 4; and strain gauges 6 being provided on each of the first strain beam 4, the second strain beam 3 and the third strain beam 5.

[0059] In this embodiment, the shape of the fixing block 1 is preferably a cuboid and a thin plate design. The first positioning hole 11 can pass through the fixing block 1 along the thickness direction so that the three-dimensional force sensor can be fixed to the end of the robotic arm through a locking member (such as a bolt).

[0060] In this embodiment, assuming that the x-axis is the first direction, the y-axis is the second direction, and the z-axis is the third direction, and the x-axis, y-axis, and z-axis are orthogonal to each other, the first strain beam 4, the second strain beam 3, and the third strain beam 5 are arranged along the first direction, the second direction, and the third direction, respectively.

[0061] In this embodiment, the first strain beam 4, the second strain beam 3, and the third strain beam 5 are thin plate-like in shape, making it easier to measure even small deformations of the first, second, and third strain beams 4, 3, and 5. Preferably, the larger surface area of the first strain beam 4 is perpendicular to the third direction, the larger surface area of the second strain beam 3 is perpendicular to the first direction, and the larger surface area of the third strain beam 5 is perpendicular to the second direction. Strain beams of the same type have the same dimensions. Of course, in other embodiments, the strain effects of the strain beams can be modified by varying the thickness, height, and width of the strain beams, thereby affecting the sensitivity of the sensor.

[0062] In this embodiment, the three-dimensional force sensor features low coupling and high sensitivity, primarily for applications requiring high force control and measurement accuracy, such as aerospace robotic arms and precision parts replacement. When a force is applied to the three-dimensional force sensor, the corresponding strain beam undergoes a small strain. Strain gauges attached to the strain beam convert this strain into an electrical signal, which is then collected and processed by subsequent circuitry to measure relatively small forces. Furthermore, because the strain beams in the three directions are arranged perpendicular to each other, interdimensional coupling is reduced, improving the sensor's measurement accuracy.

[0063] like Figure 1As shown, the three-dimensional force sensor further includes a loading block 2, which is sleeved on the third strain beam 5, and is provided with at least one second positioning hole 21. Preferably, the number of the second positioning holes 21 is multiple and evenly distributed on the surface of the loading block 2. For example Figure 1 There are four second positioning holes 21 in the loading block 2, and the loading block 2 is in the shape of a flat rectangular parallelepiped. The four second positioning holes 21 are respectively arranged at the four corners of the rectangular parallelepiped and can completely or partially penetrate the loading block 2. The second positioning holes 21 can be used to connect tools at the end of the robotic arm, such as a gripper, a torque wrench, etc., and external force can be applied to the strain beam on the three-dimensional force sensor through the loading block 2. Preferably, the mounting planes of the fixed block 1 and the loading block 2 are perpendicular to each other, which allows the three strain beams to be distributed perpendicular to each other, greatly reducing the inter-dimensional coupling of the three-dimensional force sensor and improving the measurement accuracy of the sensor.

[0064] As an optional embodiment, the first side surface and the second side surface are integrally formed; the second side surface is the plane on which the second strain beam lies along its length. In other embodiments, the first strain beam is fixedly connected to the main structure, and the first strain beam and the third strain beam are detachably connected or integrally formed; the third strain beam is connected to the center of the two first strain beams, and the first strain beam is connected to the center of the two second strain beams on the same main structure. This three-dimensional force sensor is an integrally formed structure, preferably a symmetrical structure, and can be manufactured from a single piece of material. This eliminates gaps and hysteresis caused by assembly, thereby improving the sensor's service life and measurement accuracy.

[0065] like Figure 2 As shown, in this embodiment, the strain gauges provided on the third strain beam are third strain gauges, and the number of third strain gauges is 2n, where n is a positive integer greater than 1; the third strain gauges are arranged in pairs on both sides of the third strain beam. Preferably, the value of n is 2, and every four third strain gauges form a full-bridge circuit. The connection diagram of the full-bridge circuit is shown in FIG. Figure 3 As shown, the four strain gauges on the third strain beam correspond to R1, R2, R3, and R4 in the full-bridge circuit respectively.

[0066] As an optional embodiment, the strain gauge provided on the first strain beam is a first strain gauge, and the number of first strain gauges provided on each first strain beam is two, and the two first strain gauges are provided on the top surface or the bottom surface of the first strain beam; every four first strain gauges form a full-bridge circuit. The connection diagram of the full-bridge circuit is as follows Figure 3 As shown, the four strain gauges on the first strain beam correspond to R1, R2, R3, and R4 in the full-bridge circuit respectively.

[0067] As an optional embodiment, at least two second strain beams are provided with second strain gauges, and each second strain beam is provided with two second strain gauges, and the two second strain gauges are provided on the outer side of the second strain beam; and every four second strain gauges form a full-bridge circuit. The connection diagram of the full-bridge circuit is shown in FIG. Figure 3 As shown, the four strain gauges on the second strain beam correspond to R1, R2, R3, and R4 in the full-bridge circuit respectively.

[0068] In the present application, the second strain beam 3 is connected between the two fixed blocks 1, and the second strain beam 3 is distributed perpendicular to the fixed blocks 1; the first strain beam 4 is connected between the two second strain beams 3, and the first strain beam 4 is distributed perpendicular to the second strain beam 3; the third strain beam 5 is connected between the loading block 2 and the first strain beam 4, and the third strain beam 5 is distributed perpendicular to the first strain beam 4; the center plane of the loading block 2 along the third direction is the symmetry plane; the fixed block 1 and the strain beams are symmetrically distributed, so there are two first strain beams 4, four second strain beams 3, and two third strain beams 5.

[0069] Four strain gauges 6 are attached to each of the three strain beams, and a total of 12 strain gauges 6 are attached to a three-dimensional force sensor. The four strain gauges on each strain beam form a full-bridge circuit, and there are three full-bridge circuits in total to measure the force in three directions. Figure 2 The number of the first strain gauge, the second strain gauge, and the third strain gauge are 4 respectively. The first strain gauge includes the first strain gauge a (61), the first strain gauge b (62), the first strain gauge c (63), and the first strain gauge d (64). The second strain gauge includes the second strain gauge a (65), the second strain gauge b (66), the second strain gauge c (67), and the second strain gauge d (68). The third strain gauge includes the third strain gauge a (69), the third strain gauge b (610), the third strain gauge c (611), and the third strain gauge d (612).

[0070] like Figure 4-Figure 6 As shown, two strain gauges 6 are attached to the surfaces of the two first strain beams 4 along the third direction. The two strain gauges 6 of each first strain beam 4 are on the same surface. The strain gauges are located outside the two first strain beams 4 and are symmetrically distributed with respect to the center plane of the first strain beam 4 along the first direction. Figure 6 It can be seen that when the three-dimensional force sensor is subjected to a force in the third direction, the strain of the first strain beam 4 is the largest. Therefore, the strain gauge 6 should be set close to the connection between the first strain beam 4 and the third strain beam 5. In addition, it can be seen that the coupling in other dimensions can be almost ignored.

[0071] On the basis of the above embodiments, two of the four second strain beams 3 are selected along the first direction, and two strain gauges 6 are attached to the surfaces of the two selected second strain beams 3 along the first direction, respectively. The two strain gauges 6 of each second strain beam 3 are on the same surface, and the strain gauges 6 are located outside the two second strain beams 3 and are symmetrically distributed about the center plane of the second strain beam 3 along the second direction. Figure 4 It can be seen that when the three-dimensional force sensor is subjected to a force in the first direction, the strain of the second strain beam 4 is the largest. Therefore, the strain gauge 6 should be set close to the connection between the first strain beam 4 and the second strain beam 3. In addition, it can be seen that the coupling in other dimensions can be almost ignored.

[0072] On the basis of the above embodiments, two strain gauges 6 are attached to the surfaces of the two third strain beams 5 along the second direction, and the two strain gauges 6 of each third strain beam 5 are symmetrically distributed about the center plane of the third strain beam 5 along the second direction. The strain gauges 6 on the four third strain beams 5 are symmetrically distributed about the center plane of the loading block 2 along the third direction. Figure 5 It can be seen that when the three-dimensional force sensor is subjected to a force in the second direction, the strain of the third strain beam 4 is the largest. Therefore, the strain gauge 6 should be set close to the connection between the third strain beam 5 and the loading block 2. In addition, it can be seen that the coupling in other dimensions can be almost ignored.

[0073] Specifically, such as Figure 2 It can be seen that the first strain gauge a (61), the first strain gauge b (62), the first strain gauge c (63) and the first strain gauge d (64) are pasted on the first strain beam 4; the second strain gauge includes the second strain gauge a (65), the second strain gauge b (66), the second strain gauge c (67) and the second strain gauge d (68) are pasted on the second strain beam 3; the third strain gauge includes the third strain gauge a (69), the third strain gauge b (610), the third strain gauge c (611) and the third strain gauge d (612) are pasted on the third strain beam 5.

[0074] Among them, such as Figure 3 As shown, the first strain gauge a (61), the first strain gauge b (62), the first strain gauge c (62) and the first strain gauge d (64) constitute a strain bridge a; the second strain gauge a (65), the second strain gauge b (66), the second strain gauge c (67) and the second strain gauge d (68) constitute a strain bridge b; the third strain gauge a (69), the third strain gauge b (610), the third strain gauge c (611) and the third strain gauge d (612) constitute a strain bridge c; the strain bridge a is used to measure Fz, the strain bridge b is used to measure Fx, and the strain bridge c is used to measure Fy.

[0075] Specifically, the connection positions of the four strain gauges 6 on each strain beam in the full-bridge circuit have certain requirements, such as Figure 3The diagram shows a schematic diagram of a Wheatstone full-bridge circuit for strain gauges 6 on the third strain beam 5 provided in an embodiment of the present application. Two strain gauges 6 with the same tensile and compressive strains should be located on opposite sides of the full-bridge circuit, such as first strain gauge a (61) and first strain gauge b (62) located on opposite sides of the full-bridge circuit, to improve the sensitivity of the three-dimensional force sensor. The locations of the strain gauges in the first and second directions in the corresponding strain beams are similar and will not be elaborated here.

[0076] In a second aspect, the present invention also provides a robotic arm, comprising a robotic arm body and a three-dimensional force sensor; the robotic arm body is provided with at least one third positioning hole; the three-dimensional force sensor is the three-dimensional force sensor of the first aspect of the present invention, and the three-dimensional force sensor is detachably arranged at the end of the robotic arm body, and the second positioning hole and the third positioning hole are fixed by a locking piece.

[0077] The present invention can achieve the following technical effects:

[0078] The present invention provides a three-dimensional force sensor and a robotic arm. The three-dimensional force sensor includes two main structures arranged vertically, two first strain beams, and a third strain beam. Each main structure includes two oppositely arranged first side surfaces and two oppositely arranged second side surfaces, the first and second side surfaces being perpendicular to each other. Each first side surface is provided with a fixing block having at least one first positioning hole. Each second side surface is provided with a second strain beam. Each first strain beam is arranged perpendicularly between two second strain beams of the same main structure. The third strain beam is arranged perpendicularly between two first strain beams. Strain gauges are provided on each of the first, second, and third strain beams. By arranging strain beams in three mutually perpendicular directions, the three-dimensional force sensor of the above scheme can reduce inter-dimensional coupling and improve the measurement accuracy of the sensor.

[0079] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0080] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0081] The above specific embodiments of the present invention do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A three-dimensional force sensor, characterized in that: include: Two main body structures are arranged above and below, each of the main body structures includes two first side surfaces and two second side surfaces that are oppositely arranged, the first side surfaces and the second side surfaces are perpendicular to each other, each of the first side surfaces is provided with a fixing block, and the fixing block is provided with at least one first positioning hole; each of the second side surfaces is provided with a second strain beam; Two first strain beams, each of the first strain beams is vertically arranged between two second strain beams of the same main body structure; a third strain beam, vertically arranged between the two first strain beams; The first strain beam, the second strain beam and the third strain beam are all provided with strain gauges; Also includes: a loading block, sleeved on the third strain beam, and provided with at least one second positioning hole; The strain gauges provided on the third strain beam are third strain gauges, and the number of the third strain gauges is 2n, where n is a positive integer greater than 1; the third strain gauges are arranged in pairs on both sides of the third strain beam; and every four third strain gauges form a full-bridge circuit; The strain gauges provided on the first strain beams are first strain gauges. Two first strain gauges are provided on each first strain beam, and the two first strain gauges are provided on the top surface or the bottom surface of the first strain beam. Every four first strain gauges form a full-bridge circuit. At least two of the second strain beams are provided with second strain gauges. Each second strain beam has two second strain gauges, and the two second strain gauges are provided on the outer side surfaces of the second strain beam. Every four second strain gauges form a full-bridge circuit.

2. The three-dimensional force sensor according to claim 1, wherein: There are multiple second positioning holes, which are evenly distributed on the surface of the loading block.

3. The three-dimensional force sensor according to claim 1, wherein: The first strain beam, the second strain beam and the third strain beam are in the shape of thin plates.

4. The three-dimensional force sensor according to claim 1, wherein: The first side surface and the second side surface are integrally formed; the second side surface is a plane where the second strain beam is located along the length direction.

5. The three-dimensional force sensor according to claim 1, wherein: The first strain beam is fixedly connected to the main body structure, and the first strain beam and the third strain beam are detachably connected or integrally formed; The third strain beam is connected to the center of the two first strain beams, and the first strain beam is connected to the center of the two second strain beams on the same main body structure.

6. A robotic arm, characterized in that: include: The robot arm body is provided with at least one third positioning hole; The three-dimensional force sensor is a three-dimensional force sensor as described in any one of claims 1 to 5, wherein the three-dimensional force sensor is detachably arranged at the end of the robotic arm body, and the second positioning hole and the third positioning hole are fixed by a locking piece.

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