Three-dimensional contact force measuring device and measuring method

Abstract

The application relates to a three-dimensional contact force measuring device and a measuring method, which comprises a three-dimensional contact force measuring platform, a base and a strain measuring device, the three-dimensional contact force measuring platform comprises a measuring square plate, an X plate, a Y plate, a Z plate and a connecting plate, the measuring square plate is connected with the X plate, the Y plate is connected with the X plate, the Z plate is connected with the Y plate, the connecting plate is connected with the Z plate, the three-dimensional contact force measuring platform is connected with the base through the connecting plate, two surfaces of the X plate are respectively provided with X-direction strain gauges, X-direction strain gauge terminals are arranged on the base, two surfaces of the Y plate are respectively provided with Y-direction strain gauges, Y-direction strain gauge terminals are arranged on the base, two surfaces of the Z plate are respectively provided with Z-direction strain gauges, Z-direction strain gauge terminals are arranged on the base, and the strain measuring device is connected with the strain gauge terminals through strain gauge wires. Compared with the prior art, the X plate, the Y plate and the Z plate are designed to install X-direction, Y-direction and Z-direction strain gauges, so that three-dimensional contact force measurement can be realized.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional contact force measurement technology, and in particular to a three-dimensional contact force measurement device and method. Background Technology

[0002] Most existing contact force measuring devices currently use the piezoelectric effect to measure contact force. However, this method can often only measure contact force in one direction and cannot measure multiple directions simultaneously. Due to limitations in material properties, the accuracy of the measuring devices is often insufficient, resulting in inaccurate measurement results. Furthermore, it is difficult for contact force measuring devices to achieve a large range of measurements while ensuring accuracy.

[0003] Therefore, it is necessary to design a contact force measuring device that can simultaneously measure forces in three directions with high accuracy and a large measurement range. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a three-dimensional contact force measuring device.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A three-dimensional contact force measuring device includes a three-dimensional contact force measuring platform, a base, and a strain measuring device. The three-dimensional contact force measuring platform includes a measuring square plate, an X plate, a Y plate, a Z plate, and a connecting plate.

[0007] The measuring square plate is connected to the first end of the X plate, the first end of the Y plate is connected to the second end of the X plate, the first end of the Z plate is connected to the second end of the Y plate, and the connecting plate is connected to the second end of the Z plate. The three-dimensional contact force measuring platform is connected to the base through the connecting plate. The X direction is perpendicular to the surface of the X plate, the Y direction is perpendicular to the surface of the Y plate, and the Z direction is perpendicular to the surface of the Z plate. The X, Y, and Z directions are perpendicular to each other.

[0008] The X-plate has X-direction strain gauges on both sides to form a half-bridge circuit, and the base has X-direction strain gauge terminals adapted to the X-direction strain gauges. The Y-plate has Y-direction strain gauges on both sides to form a half-bridge circuit, and the base has Y-direction strain gauge terminals adapted to the Y-direction strain gauges. The Z-plate has Z-direction strain gauges on both sides to form a half-bridge circuit, and the base has Z-direction strain gauge terminals adapted to the Z-direction strain gauges.

[0009] The strain measurement device is connected to the X-direction strain gauge terminal, Y-direction strain gauge terminal and Z-direction strain gauge terminal respectively via strain gauge wires.

[0010] Furthermore, the first end of the Y plate and the second end of the X plate are connected by a rounded chamfer.

[0011] Furthermore, the three-dimensional contact force measurement platform also includes a transition section, through which the first end of the Z plate and the second end of the Y plate are connected.

[0012] Furthermore, the three-dimensional contact force measurement platform also includes an upper top plate, which is positioned above the Z-plate. One end of the upper top plate is connected to the first end of the Z-plate via an anti-torsion column, and the other end of the upper top plate is connected to a connecting plate.

[0013] Furthermore, the connecting plate is provided with through holes, and the base is provided with bolt holes, and the connecting plate and the base are connected by bolts.

[0014] Furthermore, the measuring plate is provided with multiple connection holes.

[0015] Furthermore, the base is also provided with multiple wire holes, and the strain gauge wires connected to the X-direction strain gauge terminals, Y-direction strain gauge terminals and Z-direction strain gauge terminals are respectively connected to the strain measuring device through the wire holes.

[0016] Furthermore, the three-dimensional contact force measurement platform and base are manufactured by photopolymerization 3D printing.

[0017] A three-dimensional contact force measurement method, using the aforementioned three-dimensional contact force measurement device, includes the following steps:

[0018] The three-dimensional contact force measuring device is calibrated to determine the strain obtained by different forces acting on the measuring plate along the X direction, the strain obtained by different forces acting on the measuring plate along the Y direction, and the strain obtained by different forces acting on the measuring plate along the Z direction.

[0019] Based on the changes in strain of the X, Y, and Z plates corresponding to the forces applied in the X, Y, and Z directions to the measuring plate, the transformation matrix of force and strain is obtained.

[0020] A three-dimensional force is applied to the measuring plate of the three-dimensional contact force measuring device to obtain the strain of the X plate, Y plate and Z plate, and the contact force applied to the measuring plate is obtained according to the transformation matrix.

[0021] Furthermore, calibrating the three-dimensional contact force measuring device specifically involves:

[0022] The rotating three-dimensional contact force measuring device makes gravity perpendicular to the X plate. After the strain is zeroed, forces of different magnitudes along the X direction are applied to the measuring square plate and the corresponding strains are recorded.

[0023] The rotating three-dimensional contact force measuring device makes gravity perpendicular to the Y plate. After the strain is zeroed, forces of different magnitudes along the Y direction are applied to the measuring square plate and the corresponding strains are recorded.

[0024] The rotating three-dimensional contact force measuring device makes gravity perpendicular to the Z-plate. After the strain is zeroed, forces of different magnitudes along the Z-direction are applied to the measuring plate and the corresponding strains are recorded.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention designs X plate, Y plate and Z plate to install X direction strain gauge, Y direction strain gauge and Z direction strain gauge. The relationship between the applied force and the deformation of the plate is obtained by calibration. Then, by inverse calculation and measuring the deformation of the plate, the three-dimensional contact force can be measured.

[0027] (2) The measuring device provided by the present invention has a measurement accuracy of mN level by means of a highly sensitive semiconductor strain gauge and a thin plate thickness.

[0028] (3) By measuring structural deformation using strain gauges, the measuring device provided by this invention has a good range. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a three-dimensional contact force measuring device;

[0030] Figure 2 This is a schematic diagram of the structure of a three-dimensional contact force measurement platform;

[0031] Figure 3 This is a schematic diagram of a strain gauge half-bridge circuit;

[0032] Figure 4 This is a schematic diagram of the base structure;

[0033] Figure 5 This is a schematic diagram of the calibration of a three-dimensional contact force measuring device. In the figure, (a) is the calibration in the X direction, (b) is the calibration in the Y direction, and (c) is the calibration in the Z direction.

[0034] Reference numerals: 1. Three-dimensional contact force measurement platform; 2. Base; 101. Measuring square plate; 102. X-plate; 103. Y-plate; 104. Z-plate; 105. Anti-torsion column; 106. Top plate; 107. X-direction strain gauge; 108. X-direction strain gauge; 109. Y-direction strain gauge; 110. Y-direction strain gauge; 111. Z-direction strain gauge; 112. Z-direction strain gauge; 113. Connecting plate; 114. Transition section; 201. X-direction strain gauge terminal; 202. X-direction strain gauge terminal; 203. Y-direction strain gauge terminal; 204. Y-direction strain gauge terminal; 205. Z-direction strain gauge terminal; 206. Z-direction strain gauge terminal; 207. Wire hole; 208. Wire hole; 209. Wire hole; 210. Wire hole; 211. Wire hole; 212. Wire hole. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer and show the mating relationships between the components, some parts in the drawings have been appropriately scaled down, and the distances between the components have been increased or decreased.

[0037] In the description of the embodiments of this application, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly placed when the product of this application is used, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or component 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 this application.

[0038] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0039] In the description of the embodiments of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set," "install," "connect," and "link" 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 application based on the specific circumstances.

[0040] A three-dimensional contact force measuring device, such as Figure 1 As shown, the device includes a three-dimensional contact force measurement platform 1, a base 2, and a strain measurement device. The three-dimensional contact force measurement platform 1 includes a measuring square plate 101, an X plate 102, a Y plate 103, a Z plate 104, and a connecting plate 113. The measuring square plate 101 is connected to the first end of the X plate 102, the first end of the Y plate 103 is connected to the second end of the X plate 102, the first end of the Z plate 104 is connected to the second end of the Y plate 103, and the connecting plate 113 is connected to the second end of the Z plate 104. The three-dimensional contact force measurement platform 1 is connected to the base 2 through the connecting plate 113. The X direction is perpendicular to the surface of the X plate 102, the Y direction is perpendicular to the surface of the Y plate 103, and the Z direction is perpendicular to the surface of the Z plate 104. The X, Y, and Z directions are mutually perpendicular. Strain gauges (107 and 108) in the X direction are respectively provided on both sides of the X plate 102, forming a half-bridge loop. The base 2 is equipped with X-direction strain gauge terminals (201 and 202) adapted to the X-direction strain gauges (107 and 108). Y-direction strain gauges (109 and 110) are respectively provided on both sides of the Y-plate 103 to form a half-bridge circuit. Y-direction strain gauge terminals (203 and 204) adapted to the Y-direction strain gauges (109 and 110) are provided on the base 2. Z-direction strain gauges (111 and 112) are respectively provided on both sides of the Z-plate 104 to form a half-bridge circuit. Z-direction strain gauge terminals (205 and 206) adapted to the Z-direction strain gauges (111 and 112) are provided on the base 2. The strain measuring device is connected to the X-direction strain gauge terminals (201 and 202), Y-direction strain gauge terminals (203 and 204), and Z-direction strain gauge terminals (205 and 206) respectively through strain gauge wires.

[0041] Specifically, the structure of the three-dimensional contact force measurement platform 1 is as follows: Figure 2As shown, the three-dimensional contact force measurement platform 1 is entirely fabricated using photopolymer 3D printing. The measuring square plate 101 is connected to the X plate 102. The measuring square plate 101 has multiple connection holes for applying forces in different directions during calibration. In this embodiment, circular holes are provided at the four corners of the measuring square plate 101 as connection holes. In other embodiments, the connection holes can be flexibly adjusted as needed to facilitate calibration by applying forces in different directions through the measuring square plate 101. The X plate 102 and Y plate 103 are connected by rounded chamfers to avoid stress concentration. The Z plate 104 and Y plate 103 are connected by a transition section 114. The purpose of the transition plate is to facilitate the attachment of the Y-direction strain gauge 110. The top plate 106 is placed on the Z plate 102. Above 04, one end of the upper top plate 106 is connected to the Z plate 104 via an anti-torsion column 105, and the other end of the upper top plate 106 is connected to the connecting plate 113. The upper top plate 106 is used to offset part of the weight of the main body of the X plate 102 and Y plate 103 and reduces the mass by hollowing out. The anti-torsion column 105 is used to connect the upper top plate 106 and the Z plate 104. The setting of the upper top plate 106 and the anti-torsion column 105 achieves torque cancellation on the one hand, and prevents the gravity of the measuring square plate 101, X plate 102, and Y plate 103 from affecting the Z plate 104 on the other hand. In this embodiment, the Z plate 104 is connected to the upper top plate 106 via four anti-torsion columns 105. The connecting plate 113 has through holes, and the base 2 has bolt holes. The connecting plate 113 and the base 2 are connected by bolts. In this embodiment, the connecting plate 113 is a square plate with four through holes. The three-dimensional contact force measurement platform 1 and the base 2 are connected through the four through holes and bolts 3, 4, 5, and 6. X-direction strain gauges 107 and 108 are attached to both sides of the X-plate 102 to form a half-bridge circuit for measuring the contact force in the X direction. Y-direction strain gauges 109 and 110 are attached to both sides of the Y-plate 103 to form a half-bridge circuit for measuring the contact force in the Y direction. Z-direction strain gauges 111 and 112 are attached to both sides of the Z-plate 104 to form a half-bridge circuit for measuring the contact force in the Z direction. The schematic diagram of the strain gauge half-bridge circuit is shown below. Figure 3 As shown.

[0042] Base 2 is also manufactured as a whole by photopolymer 3D printing, and the structure of base 2 is as follows: Figure 4As shown, the shape of the base 2 is adapted to the three-dimensional contact force measurement platform 1. The base 2 also has multiple wire holes (207-212), through which strain gauge wires connected to the X-direction strain gauge terminals, Y-direction strain gauge terminals, and Z-direction strain gauge terminals are respectively connected to the strain measurement device. In this embodiment, the X-direction strain gauge terminal 201 is connected to the X-direction strain gauge 107 via a strain gauge wire, and the X-direction strain gauge terminal 202 is connected to the X-direction strain gauge 108 via a strain gauge wire. The X-direction strain gauge terminal 201 is connected to the external strain measurement device via a wire through wire hole 207, and the X-direction strain gauge terminal 202 is connected to the external strain measurement device via a wire through wire hole 208. Y-direction strain gauge terminal 203 is connected to Y-direction strain gauge 109 via strain gauge wires. Y-direction strain gauge terminal 204 is connected to Y-direction strain gauge 110 via strain gauge wires. Y-direction strain gauge terminal 203 is connected to an external strain measuring device via wire through wire hole 209, and Y-direction strain gauge terminal 204 is connected to an external strain measuring device via wire through wire hole 210. Z-direction strain gauge terminal 205 is connected to Z-direction strain gauge 111 via strain gauge wires. Z-direction strain gauge terminal 206 is connected to Z-direction strain gauge 112 via strain gauge wires. Z-direction strain gauge terminal 205 is connected to an external strain measuring device via wire through wire hole 211, and Z-direction strain gauge terminal 206 is connected to an external strain measuring device via wire through wire hole 212.

[0043] A three-dimensional contact force measurement method, using the aforementioned three-dimensional contact force measurement device, includes the following steps:

[0044] (1) Calibrate the three-dimensional contact force measuring device to determine the strain obtained by different forces acting on the measuring plate 101 along the X direction, the strain obtained by different forces acting on the measuring plate 101 along the Y direction, and the strain obtained by different forces acting on the measuring plate 101 along the Z direction; wherein, the calibration of the three-dimensional contact force measuring device specifically includes:

[0045] like Figure 5 As shown, the rotating three-dimensional contact force measuring device is used to make gravity perpendicular to the X plate 102, i.e., along the X direction, in order to eliminate the influence of gravity. After the strain is zeroed, forces of different magnitudes along the X direction are applied to the measuring square plate 101 and the corresponding strains are recorded. The rotating three-dimensional contact force measuring device is used to make gravity perpendicular to the Y plate 103, i.e., along the Y direction, in order to eliminate the influence of gravity. After the strain is zeroed, forces of different magnitudes along the Y direction are applied to the measuring square plate 101 and the corresponding strains are recorded. The rotating three-dimensional contact force measuring device is used to make gravity perpendicular to the Z plate 104, i.e., along the Z direction, in order to eliminate the influence of gravity. After the strain is zeroed, forces of different magnitudes along the Z direction are applied to the measuring square plate 101 and the corresponding strains are recorded.

[0046] (2) Based on the changes in strain of plate X102, plate Y103, and plate Z104 corresponding to the forces applied in the X, Y, and Z directions to the measuring plate 101, the force-strain transformation matrix is ​​obtained as follows:

[0047]

[0048] Where, ε i F represents the strain of the plate in the i-direction. i C represents the force in the direction of i. ij This represents the change in strain produced by the force applied in the i direction on the plate in the j direction.

[0049] (3) Apply a three-dimensional force to the measuring plate 101 of the three-dimensional contact force measuring device, obtain the strain of the X plate 102, Y plate 103, and Z plate 104, and obtain the contact force applied to the measuring plate 101 according to the transformation matrix, as follows:

[0050]

[0051]

[0052] The present invention designs X plate 102, Y plate 103 and Z plate 104 to install X-direction strain gauges, Y-direction strain gauges and Z-direction strain gauges. By calibration, the relationship between the applied force and the deformation of the plate is obtained. Then, by inverse calculation and measurement of the deformation of the plate, the three-dimensional contact force can be measured.

[0053] By utilizing a highly sensitive semiconductor strain gauge and a relatively thin plate thickness, the measuring device provided by this invention achieves a measurement accuracy at the mN level.

[0054] By measuring structural deformation using strain gauges, the measuring device provided by this invention has a good measurement range.

[0055] The purpose of this application is to design a contact force measuring device capable of simultaneously measuring forces in three directions with high accuracy and a large measurement range. Based on the bending characteristics of thin plates, three-dimensional contact force measurement is achieved through three orthogonal thin plates in three directions. Deformation is measured primarily through half-bridge circuits in the X, Y, and Z orthogonal directions. First, a standard mass weight is loaded, and the corresponding strain is measured. Based on this calibration result, the relationship matrix between the deformation of the measuring device and the applied force is obtained through least squares. Therefore, when a force is applied to the measuring plate, the corresponding deformation can be measured in real time through strain gauges on the three plates. Then, the applied force is deduced by inversely using the known calibrated relationship matrix, thus achieving three-dimensional contact force measurement. This contact force measuring device can achieve mN-level measurement accuracy by attaching high-sensitivity semiconductor strain gauges. Furthermore, since the deformation of the thin plate is related to the plate thickness, the measurement accuracy can be further improved by appropriately reducing the plate thickness. Moreover, since the contact force measurement is achieved through structural deformation, the measurement range depends on the linear deformation limit of the plate; therefore, the device can achieve a good measurement range through reasonable material selection and manufacturing.

[0056] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A three-dimensional contact force measuring device, characterized by, The three-dimensional contact force measuring platform comprises a measuring square plate, an X plate, a Y plate, a Z plate and a connecting plate, and a base and a strain measuring device are further included. The measuring square plate is connected with the first end of the X plate, the first end of the Y plate is connected with the second end of the X plate, the first end of the Z plate is connected with the second end of the Y plate, and the connecting plate is connected with the second end of the Z plate. The first end of the Y plate is connected with the second end of the X plate through a circular chamfer, and the first end of the Z plate is connected with the second end of the Y plate through a transition section. The X plate is provided with X-direction strain gauges on both sides and forms a half-bridge circuit, the base is provided with X-direction strain gauge terminals matched with the X-direction strain gauges, the Y plate is provided with Y-direction strain gauges on both sides and forms a half-bridge circuit, the base is provided with Y-direction strain gauge terminals matched with the Y-direction strain gauges, and the Z plate is provided with Z-direction strain gauges on both sides and forms a half-bridge circuit, and the base is provided with Z-direction strain gauge terminals matched with the Z-direction strain gauges. The strain measuring device is connected with the X-direction strain gauge terminals, the Y-direction strain gauge terminals and the Z-direction strain gauge terminals through strain gauge wires.

2. A three-dimensional contact force measurement device according to claim 1, wherein, The connecting plate is provided with a through hole, the base is provided with a bolt hole, and the connecting plate and the base are connected through a bolt.

3. The three-dimensional contact force measurement device of claim 1, wherein, The measuring square plate is provided with a plurality of connecting holes.

4. The three-dimensional contact force measurement device of claim 1, wherein, The base is further provided with a plurality of wire holes, and the strain gauge wires connected with the X-direction strain gauge terminals, the Y-direction strain gauge terminals and the Z-direction strain gauge terminals are connected with the strain measuring device through the wire holes.

5. The three-dimensional contact force measurement device of claim 1, wherein, The three-dimensional contact force measuring platform and the base are made of light-cured 3D printing.

6. A method of measuring three-dimensional contact forces, characterized by, The three-dimensional contact force measuring device is used for contact force measurement, comprising the following steps: The three-dimensional contact force measuring device is calibrated to determine the strain obtained by different forces in the X direction acting on the measuring square plate, the strain obtained by different forces in the Y direction acting on the measuring square plate, and the strain obtained by different forces in the Z direction acting on the measuring square plate. According to the changes of the X plate, the Y plate and the Z plate strain corresponding to the X, Y and Z direction forces applied to the measuring square plate, a transformation matrix of force and strain is obtained. A three-dimensional force is applied to the measuring square plate of the three-dimensional contact force measuring device to obtain the strain of the X plate, the Y plate and the Z plate, and the contact force applied to the measuring square plate is obtained according to the transformation matrix.

7. A method of measuring three-dimensional contact forces according to claim 6, wherein, The calibration of the three-dimensional contact force measuring device comprises the following steps: The three-dimensional contact force measuring device is rotated to make the gravity perpendicular to the X plate, and after the strain is zeroed, different sizes of forces in the X direction are applied to the measuring square plate and the corresponding strain is recorded. The rotating three-dimensional contact force measuring device makes the gravity vertical to the Y plate, and after the strain is cleared, different sizes of forces along the Y direction are applied to the measuring square plate and the corresponding strains are recorded; The rotating three-dimensional contact force measuring device makes the gravity vertical to the Z plate, and after the strain is cleared, different sizes of forces along the Z direction are applied to the measuring square plate and the corresponding strains are recorded.

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