Precision Adjustable Positioning Fixture and Positioning Method

Abstract

This invention provides a precise adjustable positioning fixture and method, belonging to the field of aerospace manufacturing engineering / aircraft assembly. It is applicable to assembly process design where the manufacturing precision of aircraft parts meets design specifications but not assembly positioning requirements, ensuring part positioning accuracy. The invention establishes theoretical positioning points on the part to locate its six degrees of freedom and determines the vector direction of each point. Horizontal / vertical positioners are installed on the positioning fixture according to the theoretical positions and vector directions of the positioning points. These positioners are equipped with a special micrometer for adjustment in the vector direction to accommodate manufacturing deviations. A clamping device is also included to clamp the part. This precise adjustable positioning fixture can adapt to manufacturing errors in product positioning characteristics. Fixture adjustments are performed on-site without additional processing; only some adjustment information is needed for rapid adjustment and reconfiguration of the fixture, achieving adjustable positioning.

Description

Technical Field

[0001] This invention belongs to the field of aerospace manufacturing engineering / aircraft assembly, and relates to a precise adjustable positioning tooling and positioning method. It is applicable to the assembly process design when the manufacturing accuracy of aircraft parts meets the design specifications but does not meet the assembly positioning requirements, thus ensuring the positioning accuracy of the parts. Background Technology

[0002] As aircraft performance has gradually improved, integrated structures have become increasingly common in aircraft design. This has led to the design of complex components, particularly those with aerodynamic features, to connect different integrated structural parts, as shown in Figures 2(a) to 2(c). Due to the multiple functions of these components, their prominent characteristics include large and discontinuous variations in curvature and predominantly sunken assembly areas. The machining or forming methods for these components are complex and their precision is unstable, resulting in the following assembly problems:

[0003] 1) The curvature of the part's shape makes it impossible to design assembly process holes in the structure, resulting in the inability to position the tooling.

[0004] 2) The manufacturing precision of the part's shape meets the aerodynamic shape requirements, but does not meet the precision requirements of the tooling positioning features, and the shape cannot be used for positioning.

[0005] 3) Although digital measurement can analyze the manufacturing deviations of parts, the manufacturing deviation information and the physical positioning tooling have not established an effective linkage, which causes on-site assembly coordination problems and excessive assembly deviations.

[0006] Traditional assembly methods cannot solve the above problems. Therefore, it is necessary to design precise and adjustable positioning tooling and positioning methods that can quickly reconstruct positioning process equipment suitable for the shape of the part based on the product's shape error on the assembly site, so as to achieve the design intent, realize the function of this type of part, and improve the level of aircraft assembly process design. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention provides a precise adjustable positioning fixture and positioning method. The precise adjustable positioning fixture is a fixture that can adapt to manufacturing errors in product positioning features. The adjustment of the fixture must be carried out on the assembly site without additional processing. Only some adjustment information is needed to complete the rapid adjustment and reconstruction of the fixture, thereby achieving adjustable positioning.

[0008] The technical solution adopted in this invention is as follows:

[0009] A precision adjustable positioning fixture includes an array base plate 1, a vertically adjustable positioner 2, a horizontally adjustable positioner 3, a horizontal clamping device 4, and a threaded clamping device 5. The number and position of each positioner and clamping device are adjusted according to the positioning requirements of part 6, as shown in Figure 4(a).

[0010] The array-type base plate 1 is a square plate structure with several threaded holes arranged in an array for installing various positioners and clamps. The array arrangement of the threaded holes allows for arbitrary adjustment of the installation positions of the positioners and clamps. The array-type base plate 1 is made of aluminum alloy.

[0011] The vertically adjustable positioner 2 includes a specially designed micrometer 7, an adapter A 8, a pad 9, a six-dimensional force sensor 10, and a bottom support 11, as shown below. Figure 6 As shown.

[0012] The specially designed micrometer 7 includes a micrometer screw 13, a rectangular frame 14, and a mounting hole 15. The specially designed micrometer 7 retains the measurement function and accuracy of a traditional electronic micrometer. While a typical micrometer measures the external dimensions of a part, this invention redesigns the micrometer, converting the measurement function into an adjustment function for a positioner. Utilizing the visualization function and high precision (up to 0.01mm) of an electronic micrometer, precise adjustment of the positioner is achieved. The anvil of the traditional micrometer is removed, and the end face of the micrometer screw 13 is modified into a spherical surface. Specifically, the head of the micrometer screw 13 is spherical for contact with part 6, and the tail is an adjustment structure for adjusting the extension and retraction of the micrometer screw 13. The micrometer screw 13 also has a display device for visualizing the adjusted dimensions. The rectangular frame 14 is arranged on the side of the micrometer screw 13, changing the original circular frame of the traditional electronic micrometer to a rectangular frame, and a mounting hole 15 is drilled for connection with the adapter A 8. Figure 8 As shown. The special micrometer 7 in the vertically adjustable positioner 2 is arranged vertically (along the Y-axis) with its head facing upwards, so that the adjustable direction is along the vertical direction, and it is used for adjustment along the vector direction of the vertical direction.

[0013] The adapter A8 is made of aluminum alloy and is used to fix the special micrometer 7 so that it always remains vertical. The adapter A8 adopts an integrated machined structure and is connected to the rectangular ruler frame 14 on the special micrometer 7 by a plug-in type. The connecting holes are drilled on the ears and are used to cooperate with the mounting holes 15 to achieve a fixed connection. The bottom surface of the adapter A8 is drilled with connecting holes for the pad 9 or the six-dimensional force sensor 10.

[0014] The six-dimensional force sensor 10 has multiple strain gauges and pressure sensors inside, and a screen on the outside. It is used to indirectly measure the force and torque of the special micrometer 7 in six directions and display the force values ​​in the six directions on the screen. The six directions refer to the X, Y, and Z axes, as well as the axial force directions of each axis. The six-dimensional force sensor 10 is connected to the lower end of the adapter A 8. When the micrometer screw 13 of the special micrometer 7 is subjected to assembly stress, it will cause the sensor output signal to change. By processing and analyzing these signals, the force state information of the adjustable positioner can be obtained. When the force value exceeds the assembly requirements, timely adjustment is made to eliminate stress and avoid over-positioning. The upper and lower surfaces of the six-dimensional force sensor 10 are drilled with threaded blind holes for fixed connection with the upper and lower components.

[0015] The bottom support 11 is made of aluminum alloy and is fixedly connected below the six-dimensional force sensor 10. It is used to connect the vertically adjustable positioner 2 to the array base plate 1.

[0016] The spacer block 9, made of aluminum alloy, is installed between the adapter A8 and the six-dimensional force sensor 10. It is used to significantly increase the height of the locator. Its rectangular shape is inexpensive, thus avoiding the need for custom-made adapters for height requirements. This makes adjusting the locator height more convenient and cost-effective. The spacer block 9 is manufactured in a series of different thicknesses at 5mm intervals to accommodate different positioning heights. The installation specification can be selected or omitted depending on the requirements. Threaded blind holes are drilled on the upper and lower surfaces of the spacer block 9 for connecting the adapter A8 and the six-dimensional force sensor 10, respectively.

[0017] The horizontally adjustable positioner 3 is based on the vertically adjustable positioner with the addition of an adapter B 12, such as... Figure 7 As shown, specifically:

[0018] The adapter B 12 is made of aluminum alloy and has a welded structure. It includes a vertical connecting plate 16 arranged in the vertical direction, a horizontal connecting plate 18 arranged in the horizontal direction, and a reinforcing rib 17 connecting the two. The adapter B 12 is fixedly connected between the adapter A 8 and the six-dimensional force sensor 10 or the pad 9. It is used to arrange the special micrometer 7 in the horizontal adjustable positioner 3 in the horizontal direction (along the X-axis or Z-axis), that is, the adjustable direction is along the horizontal direction, and it is used for adjustment in the vector direction along the horizontal direction. The vertical connecting plate 16 and the horizontal connecting plate 18 are respectively drilled with connecting holes for fixed connection between components.

[0019] The positioners in the positioning fixture are arranged according to the positioning points on part 6. Each positioning point includes at least six theoretical positioning points, which are divided into three groups to control the six degrees of freedom of part 6. The first group of three points forms a plane to control three degrees of freedom; the second group of two points forms a line to control two degrees of freedom; and the third group of one point controls the remaining one degree of freedom. The vector directions of the positioning points within each group are the same, and the vector directions between groups are perpendicular to each other, i.e., along the X, Y, and Z directions. In this way, all degrees of freedom of part 6 are controlled without over-constraint, determined by the vector directions of each theoretical positioning point. The types of positioners are as follows; in addition, based on the positioning requirements of different parts, other positioning points are appropriately added on the basis of the 6 theoretical positioning points. The vector direction of the added positioning points is one of the X, Y, and Z directions, and then the corresponding positioners are added; the positions of the 6 theoretical positioning points can be referred to Figures 3(a) to 3(c); after the part 6 is manufactured, its manufacturing error will be reflected in the displacement of the positioning point position in its vector direction, causing the positioner to interfere with or create a gap with the part 6; the contact feature between the positioner and the part 6 adopts a spherical surface to achieve point contact with the part 6. The point contact of the spherical positioner avoids the positioner coordination problem caused by the shape error of the part 6.

[0020] In the theoretical model of part 6, the spherical surface of the micrometer screw 13 head of all the positioning fixtures is in point contact with the surface of part 6, with a theoretical distance of 0. When part 6 is actually manufactured, its shape will have errors. After the point cloud formed by the shape scan is virtually assembled with the theoretical model of the positioning fixture, the spherical surface of the micrometer screw 13 will have gaps or interference with the surface of part 6. The amount of gaps or interference is the value that the positioning fixture needs to be adjusted, and this adjustment is achieved through a special micrometer 7 on the positioning fixture.

[0021] The horizontal clamping device 4 is a conventional horizontal clamping device, used in conjunction with the vertical adjustable locator 2 to provide clamping force and ensure that the part 6 remains in close contact with the locator during assembly. The clamping direction of the horizontal clamping device 4 is opposite to the positioning direction of the vertical adjustable locator 2. Its position and number are determined according to the vertical adjustable locator 2, and there are no less than two horizontal clamping devices 4. The height of the horizontal clamping device 4 is determined by its own stroke and the height of the positioning surface of the part 6. Its bottom end cooperates with the array base plate 1 to fix the horizontal clamping device 4 on the array base plate 1.

[0022] The thread clamp 5 is a conventional thread clamp, used in conjunction with the horizontally adjustable locator 3 to provide clamping force and ensure that the part 6 remains in close contact with the locator during assembly. The clamping direction of the thread clamp 5 is horizontal, and its position and number are determined by the horizontally adjustable locator 3. There are no fewer than two thread clamps 5. The height of the thread clamp 5 is determined by the height of the locating surface of the part 6. Its bottom end cooperates with the array base plate 1 to fix the thread clamp 5 on the array base plate 1, as shown in Figures 4(a) and 4(b).

[0023] A precise and adjustable positioning method, the positioning method comprising the following steps:

[0024] Step 1: Design a positioning scheme based on the shape and assembly requirements of part 6, select 6 theoretical positioning points to ensure that the 6 degrees of freedom of part 6 can be fully restricted and avoid over-constraint. According to the positioning requirements of part 6, the number of positioning points can be increased appropriately, and a theoretical model of part 6 is made, as shown in Figures 3(a) to 3(c).

[0025] Step 2: Based on the positioning scheme of part 6, determine the type of locator required for each positioning point in the positioning fixture, as well as the theoretical position of each locator. Then determine the quantity and position of each clamping device, and make a theoretical model of the positioning fixture, as shown in Figures 4(a), 4(b), 5, 6, and 7.

[0026] Step 3: The part 6 to be installed is manufactured by setting up a digital scanning device to scan the shape of part 6, ensuring that the scanning accuracy is within ±0.1mm, and forming a point cloud of part 6 to be positioned.

[0027] Step 4: Using the theoretical model of part 6 as a reference, perform optimal fitting on the point cloud of part 6. Virtually assemble the fitted point cloud with the theoretical model of the positioning fixture obtained in Step 2. Measure the 3D distance between the spherical surface of all positioner heads and the part point cloud. The vector direction of the 3D distance is the adjustable direction of the positioner. If the 3D distance is positive, the micrometer screw 13 of the positioner is extended, and the absolute value of the 3D distance is the adjustment amount. If the measured distance is negative, the micrometer screw 13 of the positioner is shortened, and the absolute value of the 3D distance is the adjustment amount. The virtual assembly method involves placing the theoretical model of the positioning fixture and the part point cloud data in the same three-dimensional environment.

[0028] Step 5: Based on the position of the locator obtained in Step 2 and the adjustment amount of each locator obtained in Step 4, supplement and improve the positioning scheme for on-site assembly.

[0029] Step 6: During on-site assembly, assemble the positioning fixtures according to the improved positioning scheme, including the installation and adjustment of the positioner and the installation of the clamping device.

[0030] Step 7: Place part 6 onto the locator. If the force value displayed on the six-dimensional force sensor 10 exceeds the assembly requirements, make timely adjustments to eliminate stress. Finally, operate each clamp to press part 6 onto the positioning fixture to complete the positioning of part 6.

[0031] The beneficial effects of this invention are as follows: This invention effectively combines digital measurement, virtual assembly analysis results with real process equipment, solves the problem of complex parts being unable to be accurately positioned on tooling, shortens the assembly cycle and greatly improves assembly accuracy, thus ensuring the assembly quality of the aircraft. Attached Figure Description

[0032] Figure 1 Flowchart for a precise and adjustable positioning method.

[0033] Figure 2(a) is an isometric view of the complex part.

[0034] Figure 2(b) is a view of Figure 2(a) from direction A.

[0035] Figure 2(c) is a view of Figure 2(b) from direction D.

[0036] Figure 3(a) is a view along line C of Figure 2(b). In the figure, points h, i, and j are the positioning points of the first group.

[0037] Figure 3(b) is a view from direction A of Figure 2(a). In the figure, points k and m are the positioning points of the second group.

[0038] Figure 3(c) is a view from direction B of Figure 2(a). In the figure, point n is the positioning point of the third group.

[0039] Figure 4(a) shows a schematic diagram of the positioning fixture structure.

[0040] Figure 4(b) shows a schematic diagram of the positioning tooling assembly.

[0041] Figure 5 This is a schematic diagram of an array-type base plate structure.

[0042] Figure 6 This is a schematic diagram of a vertically adjustable positioner.

[0043] Figure 7 This is a schematic diagram of the horizontally adjustable positioner.

[0044] Figure 8 This is a schematic diagram of a specially made micrometer.

[0045] In the diagram: 1—Array base plate; 2—Vertical adjustable positioner; 3—Horizontal adjustable positioner; 4—Horizontal clamping device; 5—Threaded clamping device; 6—Part; 7—Special micrometer; 8—Adapter A; 9—Padded block; 10—Six-dimensional force sensor; 11—Bottom support; 12—Adapter B; 13—Micrometer screw; 14—Rectangular ruler frame; 15—Assembly hole; 16—Vertical connecting plate; 17—Reinforcing rib; 18—Horizontal connecting plate. Detailed Implementation

[0046] The technical solution of the present invention will now be clearly and completely described, and examples of the embodiments are shown in the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments improved or modified by those skilled in the art based on the embodiments of the present invention are within the protection scope of the present invention.

[0047] A precise and adjustable positioning fixture utilizes point features to achieve product positioning. The specific principle is as follows:

[0048] Traditional aircraft component positioning utilizes surface and hole features. While this offers advantages such as reliable and easily achievable feature accuracy, it also imposes numerous restrictions on degrees of freedom (surfaces restrict three degrees of freedom, holes four). Furthermore, multiple feature positioning methods can lead to over-constraints, meaning there is overlap in degree-of-freedom restrictions. Traditional tooling positioners are also designed based on surface and hole features, employing surfaces, slots, holes, and pins. However, when the feature accuracy of the part is low, this design approach becomes unfeasible because the relative positions of the part features do not match the relative positions of the tooling positioner features, and over-constraints prevent the part from being positioned correctly. Therefore, this invention changes the traditional positioning method by replacing hole and surface features with point features of the part. The vector directions of the point features are unified and coordinated, avoiding coordination problems caused by over-constraints.

[0049] A three-dimensional coordinate system is established. The coordinate values ​​of the six positioning points on the theoretical model of the part are the initial positions of the locator when designing the flexible assembly fixture. The vector direction of each positioning point is the adjustable direction of the locator. Based on this, the theoretical model of the positioning fixture of this invention is designed. After the part is manufactured, its manufacturing error will be reflected in the displacement of the positions of these six positioning points in their vector directions, causing interference or gaps between the locator and the part. Since the position change of each positioning point is only a displacement in one vector direction, the positioning fixture is easy to adjust; if the positioning is not a point but a surface, it is difficult to change the shape of the fixture to adjust it. This is the advantage of this invention using point features instead of surface and hole features. The specific method for determining the theoretical positioning points is as follows, as shown in Figures 3(a) to 3(c):

[0050] 1) Select 6 points on the surface of the part. The 6 points are divided into 3 groups. The first group has 3 points, namely points h, i and j, as shown in Figure 3(a); the second group has 2 points, namely points k and m, as shown in Figure 3(b); the remaining 1 point is the third group, namely point n, as shown in Figure 3(c).

[0051] 2) The vector directions of points within each group are consistent, and the vector directions of points between groups are perpendicular to each other. Specifically, the vector directions of points h, i, and j are parallel to the Y-axis (i.e., the vertical direction), the vector directions of points k and m are parallel to the Z-axis (i.e., the horizontal direction - left and right), and the vector direction of point n is parallel to the Z-axis (i.e., the horizontal direction - front and back).

[0052] 3) The first group of 3 points h, i, j forms a plane, controlling 3 degrees of freedom of the part; the second group of 2 points k, m forms a line, controlling 2 degrees of freedom of the part; and the third group of 1 point n controls 1 degree of freedom. In this way, all 6 degrees of freedom of the part are controlled without "over-constraint".

[0053] A precision adjustable positioning fixture includes an array base plate 1, a vertically adjustable positioner 2, a horizontally adjustable positioner 3, a horizontal clamping device 4, and a threaded clamping device 5. The number and position of each positioner and clamping device are adjusted according to the positioning requirements of part 6, as shown in Figure 4(a).

[0054] The array-type base plate 1 is a square plate structure with several threaded holes arranged in an array for installing various positioners and clamping devices. The array arrangement of the threaded holes allows for arbitrary adjustment of the installation positions of the positioners and clamping devices. The array-type base plate 1 is made of aluminum alloy, with individual plate dimensions of 600×600×20 (mm). M8 threaded through holes are drilled on the surface, arranged in an array of 21 rows and 21 columns, with a hole spacing of 25±0.05mm. Each row is represented by an English letter from A to U, and each column is represented by Arabic numerals from 1 to 21. Figure 5 As shown.

[0055] The vertically adjustable positioner 2 includes a specially designed micrometer 7, an adapter A 8, a pad 9, a six-dimensional force sensor 10, and a bottom support 11, as shown below. Figure 6 As shown, in this embodiment, there are three vertically adjustable positioners 2, which are used to position the three theoretical positioning points h, i, and j on the part 6.

[0056] The specially designed micrometer 7 retains the measurement function and accuracy of a traditional electronic micrometer. While a typical micrometer measures the external dimensions of parts, this invention redesigns the micrometer, converting the measurement function into an adjustment function for a positioner. Utilizing the visualization function and high precision (up to 0.01mm) of the electronic micrometer adjustment, precise adjustment of the positioner is achieved. The anvil of the traditional micrometer is removed, and the end face of the micrometer screw 13 is modified to a spherical surface. Specifically, the specially designed micrometer 7 includes a micrometer screw 13, a rectangular frame 14, and a mounting hole 15. The head of the micrometer screw 13 is spherical for contact with part 6, and the tail is an adjustment structure for adjusting the extension and retraction of the micrometer screw 13. The micrometer screw 13 also has a display device for visualizing the adjusted dimensions. The rectangular frame 14 is arranged on the side of the micrometer screw 13, changing the original circular frame of the traditional electronic micrometer to a rectangular frame with a nominal thickness of 6mm, and drilling mounting holes 15 for connection with adapter A 8. Figure 8 As shown. The special micrometer 7 in the vertically adjustable positioner 2 is arranged vertically (along the Y-axis) with its head facing upwards, so that the adjustable direction is along the vertical direction, and it is used for adjustment along the vector direction of the vertical direction.

[0057] The adapter A8 is made of aluminum alloy and is used to fix the special micrometer 7 so that it always remains vertical. The adapter A8 adopts an integrated machined structure and is connected to the rectangular ruler frame 14 on the special micrometer 7 by a plug-in type. The nominal width of the slot is 6mm, and a connection hole is drilled on the ear plate to cooperate with the assembly hole 15 to achieve a fixed connection. The bottom surface of the adapter A8 is drilled with a connection hole for the pad 9 or the six-dimensional force sensor 10.

[0058] The six-dimensional force sensor 10 has multiple strain gauges and pressure sensors inside, and a screen on the outside. It is used to indirectly measure the force and torque of the special micrometer 7 in six directions and display the force values ​​in the six directions on the screen. The six directions refer to the X, Y, and Z axes, as well as the axial force directions of each axis. The six-dimensional force sensor 10 is connected to the adapter A 8. When the micrometer screw 13 of the special micrometer 7 is subjected to assembly stress, it will cause the sensor output signal to change. By processing and analyzing these signals, the force state information of the adjustable positioner can be obtained. When the force value exceeds the assembly requirements, timely adjustment is made to eliminate stress and avoid over-positioning. The six-dimensional force sensor 10 has threaded blind holes drilled on its upper and lower surfaces for fixed connection with the upper and lower components.

[0059] The bottom support 11 is made of aluminum alloy and is fixedly connected below the six-dimensional force sensor 10. It is used to connect the vertically adjustable positioner 2 to the array base plate 1. The nominal thickness of the bottom support 11 is 6mm. It is provided with two φ8H9 through holes with a spacing of 75±0.05mm. The fastener is an M8 hexagonal head bolt.

[0060] The spacer block 9, made of aluminum alloy, is installed between the adapter A8 and the six-dimensional force sensor 10. It is used to significantly increase the height of the locator. Its rectangular shape is inexpensive, thus avoiding the need for custom-made adapters for height requirements. This makes adjusting the locator height more convenient and cost-effective. The spacer block 9 is manufactured in a series of different thicknesses at 5mm intervals to accommodate different positioning heights. The installation specification can be selected or omitted depending on the requirements. Threaded blind holes are drilled on the upper and lower surfaces of the spacer block 9 for connecting the adapter A8 and the six-dimensional force sensor 10, respectively.

[0061] The horizontally adjustable positioner 3 is based on the vertically adjustable positioner with the addition of an adapter B 12, such as... Figure 7 As shown, in this embodiment, there are three horizontally adjustable positioners 3. Two of them are used to position the two theoretical positioning points k and m on the part 6, and their positioning directions are the same. The third position is used to position the theoretical positioning point n on the part 6, and its positioning direction is perpendicular to the positioning directions of the other two horizontally adjustable positioners 3. Specifically:

[0062] The adapter B 12 is made of aluminum alloy and has a welded structure. It includes a vertical connecting plate 16 arranged in the vertical direction, a horizontal connecting plate 18 arranged in the horizontal direction, and a reinforcing rib 17 welded between the two. The adapter B 12 is fixedly connected between the adapter A 8 and the six-dimensional force sensor 10 or the pad 9. It is used to arrange the special micrometer 7 in the horizontal adjustable positioner 3 in the horizontal direction (along the X-axis or Z-axis), that is, the adjustable direction is along the horizontal direction, and it is used for adjustment along the vector direction of the horizontal direction. Connection holes are drilled on the vertical connecting plate 16 and the horizontal connecting plate 18 respectively for fixed connection between components.

[0063] In the theoretical model state, the spherical surface of the micrometer screw 13 head of all the positioners is in point contact with the surface of part 6, with a theoretical distance of 0. When part 6 is actually manufactured, its shape will have errors. After the point cloud formed by the shape scan is virtually assembled with the theoretical model of the positioning fixture, the spherical surface of the micrometer screw 13 will have gaps or interference with the surface of part 6. The amount of gaps or interference is the value that the positioner needs to be adjusted, and this adjustment is achieved through a special micrometer 7 on the positioner.

[0064] The horizontal clamping device 4 is a conventional horizontal clamping device, used in conjunction with the vertical adjustable locator 2 to provide clamping force and ensure that the part 6 remains in close contact with the locator during assembly. The clamping direction of the horizontal clamping device 4 is opposite to the positioning direction of the vertical adjustable locator 2. Its position and number are determined according to the vertical adjustable locator 2, and there are no less than two horizontal clamping devices 4. The height of the horizontal clamping device 4 is determined by its own stroke and the positioning surface height of the part 6. An external threaded stud is provided at its bottom, which is directly connected and locked to the internal threaded hole of the array base plate 1. In this embodiment, there are two horizontal clamping devices 4. One clamping position is set directly above the positioning point of one of the three vertical adjustable locators 2, and the other is set in the middle of the positioning points of the other two vertical adjustable locators 2, fixing the position of the part 6 in the vertical direction, as shown in Figures 4(a) and 4(b).

[0065] The thread clamp 5 is a conventional thread clamp, used in conjunction with the horizontally adjustable locator 3 to provide clamping force and ensure that the part 6 remains in close contact with the locator during assembly. The position and number of the thread clamp 5 are determined according to the horizontally adjustable locator 3, and there are no less than two thread clamps 5. The height of the thread clamp 5 is determined by the height of the positioning surface of the part 6. An external threaded stud is provided at its bottom, which is directly connected and locked to the internal threaded hole of the array base plate 1. In this embodiment, there are two thread clamps 5. One of them has a clamping direction opposite to the positioning direction of the thread clamp 5 at point i, and the other is determined according to the thread clamps 5 at points k and m and the horizontal shape of the part 6, as shown in Figures 4(a) and 4(b).

[0066] A precise and adjustable positioning method, the positioning method comprising the following steps:

[0067] Step 1: Design a positioning scheme based on the shape and assembly requirements of part 6, select 6 theoretical positioning points, namely points h, i, j, k, m and n in Figures 3(a) to 3(c), to ensure that the 6 degrees of freedom of part 6 can be fully constrained and avoid over-constraint. According to the positioning requirements of part 6, add positioning points and make a theoretical model of part 6, as shown in Figures 3(a) to 3(c).

[0068] Step 2: Determine the type of locator required for each positioning point in the positioning fixture according to the positioning scheme of part 6, as well as the theoretical position of each locator, and then determine the number and position of each clamping device. In this embodiment, there are 3 vertical adjustable locators 2, which are used for positioning points h, i, and j, and their theoretical positions are determined by these 3 points. There are 3 horizontal adjustable locators 3, which are used for positioning points k, m, and n, and their theoretical positions are determined by these 3 points. The theoretical model of the positioning fixture is obtained, as shown in Figure 4(a).

[0069] Step 3: The part 6 to be installed is manufactured by setting up a digital scanning device to scan the shape of part 6, ensuring that the scanning accuracy is within ±0.1mm, and forming a point cloud of part 6 to be positioned.

[0070] Step 4: Using the theoretical model of part 6 as a reference, perform optimal fitting on the point cloud of part 6. The pose of the fitted point cloud is the optimal installation pose of the actual part. Virtually assemble the fitted point cloud with the theoretical model of the positioning fixture, and measure the 3D distance between the spherical surface of all positioner heads and the part's point cloud. The vector direction of the 3D distance is the adjustable direction of the positioner. If the 3D distance is positive, the micrometer screw 13 of the positioner is extended, and the absolute value of the 3D distance is the adjustment amount; if the measured distance is negative, the micrometer screw 13 of the positioner is shortened, and the absolute value of the 3D distance is the adjustment amount.

[0071] Step 5: Based on the position of the locator obtained in Step 2 and the adjustment amount of each locator obtained in Step 4, supplement and improve the positioning scheme for on-site assembly.

[0072] Step 6: During on-site assembly, assemble the positioning fixtures according to the improved positioning scheme, including the installation and parameter adjustment of the positioner, as well as the installation of the clamping device.

[0073] Step 7: Place part 6 onto the locator. If the force value displayed on the six-dimensional force sensor 10 exceeds the assembly requirements, make timely adjustments to eliminate stress. Finally, operate each clamp to press part 6 onto the positioning fixture to complete the positioning of part 6.

[0074] This embodiment is merely exemplary and not all embodiments. All other embodiments modified or adjusted by those skilled in the art are within the scope of protection of this invention.

Claims

1. A precision adjustable positioning fixture, characterized in that, The positioning fixture includes an array-type base plate (1), a vertically adjustable positioner (2), a horizontally adjustable positioner (3), a horizontal clamping device (4), and a threaded clamping device (5). The array-type base plate (1) is a square plate structure with several threaded holes arranged in an array for installing various positioners and clamps, so as to realize arbitrary adjustment of the installation position of the positioners and clamps; The vertically adjustable positioner (2) includes a special micrometer (7), adapter A (8), a six-dimensional force sensor (10), and a bottom support (11). The specially made micrometer (7) includes a micrometer screw (13) and a rectangular ruler frame (14); the head of the micrometer screw (13) is spherical and is used to contact the part (6), and the tail is an adjustment structure used to adjust the extension and retraction of the micrometer screw (13). The micrometer screw (13) is equipped with a display device for visual adjustment of the size; the rectangular ruler frame (14) is arranged on the side of the micrometer screw (13) and is used to connect with the adapter A (8); the specially made micrometer (7) in the vertical adjustable positioner (2) is arranged vertically with its head facing upwards; The adapter A (8) is used to fix the special micrometer (7) so that it always remains vertical. The adapter A (8) adopts an integrated machined structure and is fixedly connected to the rectangular ruler frame (14) on the special micrometer (7) by a plug-in type. The six-dimensional force sensor (10) is connected to the lower end of the adapter A (8). It has multiple strain gauges and pressure sensors inside and a body screen outside. It is used to indirectly measure the force and torque of the special micrometer (7) in six directions and display the force value on the body screen. When the force value exceeds the assembly requirements, it makes timely adjustments to eliminate stress and avoid over-positioning. The bottom support (11) is fixedly connected below the six-dimensional force sensor (10) and is used to connect the vertically adjustable positioner (2) to the array base plate (1); The horizontally adjustable positioner (3) is based on the vertically adjustable positioner, with the addition of an adapter B (12), specifically: The adapter B (12) includes a vertical connecting plate (16) arranged in the vertical direction, a horizontal connecting plate (18) arranged in the horizontal direction, and a reinforcing rib (17) connected between the two. The adapter B (12) is fixedly connected between the adapter A (8) and the six-dimensional force sensor (10) to make the special micrometer (7) in the horizontal adjustable positioner (3) arranged in the horizontal direction. The positioning fixture is arranged according to the positioning points on the part (6). In the theoretical model state of the part (6), the spherical surface of the micrometer screw (13) head of all the positioning fixtures is in point contact with the surface of the part (6), and the theoretical distance is 0. When the part (6) is actually manufactured, the spherical surface of the micrometer screw (13) and the actual surface of the part (6) will produce gap or interference. The gap or interference amount is the value that the positioning fixture needs to be adjusted. The horizontal clamping device (4) is a conventional horizontal clamping device, which is used in conjunction with the vertical adjustable positioner (2) to provide clamping force. The clamping direction of the horizontal clamping device (4) is opposite to the positioning direction of the vertical adjustable positioner (2). Its position and number are determined according to the vertical adjustable positioner (2). The height of the horizontal clamping device (4) is determined by its own working stroke and the positioning surface height of the part (6). Its bottom end is fixed in conjunction with the array base plate (1). The thread clamp (5) is a conventional thread clamp, which is used in conjunction with the horizontal adjustable positioner (3) to provide clamping force. The clamping direction of the thread clamp (5) is along the horizontal direction, and its position and number are determined according to the horizontal adjustable positioner (3). The height of the thread clamp (5) is determined by the positioning surface height of the part (6), and its bottom end is fixed in conjunction with the array base plate (1).

2. The precision adjustable positioning fixture according to claim 1, characterized in that, The positioning fixture includes at least 6 theoretical positioning points, which are divided into three groups to control the 6 degrees of freedom of the part (6). The first group of three points forms a plane to control the 3 degrees of freedom of the part (6), the second group of two points forms a line to control the 2 degrees of freedom of the part (6), and the third group of one point controls the remaining 1 degree of freedom. The vector directions of the positioning points within the group are the same, and the vector directions between groups are perpendicular to each other. This achieves the control of all degrees of freedom of the part (6) without over-constraint. The type of positioner is determined according to the vector direction of each theoretical positioning point. Based on the positioning requirements of different parts, other positioning points are appropriately added on the basis of the 6 theoretical positioning points. The vector direction of the added positioning points is the same as that of one of the theoretical positioning points, and then the corresponding positioner is added.

3. The precision adjustable positioning fixture according to claim 1, characterized in that, The number of the horizontal clamps (4) is not less than two.

4. The precision adjustable positioning fixture according to claim 1, characterized in that, The number of the thread clamps (5) is not less than two.

5. The precision adjustable positioning fixture according to claim 1, characterized in that, The positioning fixture described herein includes a vertically adjustable positioner (2) and a horizontally adjustable positioner (3), which also include a pad (9). The pad (9) is installed between the adapter A (8) or the adapter B (12) and the six-dimensional force sensor (10) to increase the height of the positioner over a wide range. The pad is rectangular and is manufactured in a series of different thicknesses at 5mm intervals to accommodate different positioning heights. The installation specifications can be selected or not installed according to the requirements.

6. A precise adjustable positioning method, implemented using the precise adjustable positioning fixture described in claim 2, characterized in that, The positioning method includes the following steps: Step 1: Design a positioning scheme based on the shape and assembly requirements of part (6), select 6 theoretical positioning points to ensure that the 6 degrees of freedom of part (6) can be fully restricted, avoid over-constraint, and make a theoretical model of part (6). Step 2: Based on the positioning scheme of part (6), determine the type of positioning device required for each positioning point in the positioning fixture, as well as the theoretical position of each positioning device, then determine the quantity and position of each clamping device, and make a theoretical model of the positioning fixture. Step 3: Scan the shape of part (6) to form a point cloud of part (6) to be positioned; Step 4: Using the theoretical model of part (6) as a reference, perform optimal fitting on the point cloud of part (6); virtually assemble the fitted point cloud with the theoretical model of the positioning fixture obtained in step 2, and measure the 3D distance between the spherical surface of all positioner heads and the point cloud of the part. The vector direction of the 3D distance is the adjustable direction of the positioner. Step 5: Based on the position of the locator obtained in Step 2 and the adjustment amount of each locator obtained in Step 4, supplement and improve the positioning scheme for on-site assembly. Step 6: During on-site assembly, assemble the positioning fixtures according to the improved positioning scheme, including the installation and adjustment of the positioner and the installation of the clamping device. Step 7: Place part (6) onto the locator. If the force value displayed on the six-dimensional force sensor (10) exceeds the assembly requirements, make timely adjustments to eliminate stress. Finally, operate each clamp to press part (6) onto the positioning fixture to complete the positioning of part (6).

7. The precise adjustable positioning method according to claim 6, characterized in that, In step 1, the number of positioning points is increased appropriately according to the positioning requirements of part (6).

8. The precise adjustable positioning method according to claim 6, characterized in that, In step 3, the scanning accuracy of part (6) is within ±0.1mm.

9. The precise adjustable positioning method according to claim 6, characterized in that, In step 4, if the 3D distance between the spherical surface of the locator head and the point cloud of the part is positive, the micrometer screw (13) of the locator is extended, and the absolute value of the 3D distance is the adjustment amount; if the measured distance is negative, the micrometer screw (13) of the locator is shortened, and the absolute value of the 3D distance is the adjustment amount.

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