A method and apparatus for calculating temperature compensation of a laser tracker used in tooling measurement

Abstract

This invention discloses a method and apparatus for calculating temperature compensation using a laser tracker for tooling measurement. This method considers not only the difference in thermal expansion coefficients between the temperature compensation plate and the main frame of the large assembly tooling, but also the anchor points of the temperature compensation plate relative to the main frame and the main frame relative to the foundation, thus obtaining a method for calculating temperature compensation at the calibration points on the temperature compensation plate of the assembly tooling. Simulation results show that the calculation method proposed in this invention can effectively eliminate temperature deformation.

Description

Technical Field

[0001] This invention belongs to the field of digital measurement technology, specifically relating to a method and apparatus for calculating temperature compensation of a laser tracker used for tooling measurement. Background Technology

[0002] In the aircraft manufacturing industry, to ensure good interchangeability and assembly coordination of aircraft parts, as well as higher overall aircraft performance, the requirements for assembly quality are becoming increasingly stringent, typically requiring assembly precision at the sub-millimeter level or even higher. However, thermal deformation is unavoidable due to changes in ambient temperature, directly affecting the assessment of the product's assembly condition. For small and medium-sized parts, thermal deformation is relatively small, and the temperature of the working environment is relatively easy to control, so the impact of temperature on the assembly condition is minimal. However, for large aircraft, due to the large dimensions of parts and components in certain dimensions, thermal deformation is significant, and the temperature in the large space is difficult to control, making the effect of temperature non-negligible. Taking a 20m long aluminum alloy as an example, its thermal deformation is approximately 2.4mm when the temperature changes by 5℃. When using a laser tracker to measure the calibration points of large tooling, directly using this measurement value for inspection and assessment of the assembly condition obviously cannot meet the requirements. Therefore, it is usually necessary to compensate for the thermal deformation caused by temperature before making an assessment.

[0003] While current laser measurement equipment possesses some temperature compensation capabilities, its compensation methods are primarily limited to scaling factor correction based on the thermal expansion coefficient of a single material. This traditional compensation method fails to adequately consider the differences in thermal expansion between different materials and the influence of anchor point positions. For large assembly fixtures with temperature compensation plates, the anchor point positions of the fixture relative to the foundation, the anchor point positions of the temperature compensation plate relative to the fixture, and the different thermal expansion coefficients between the fixture frame and the temperature compensation plate all significantly affect the temperature compensation calculation. Therefore, if the current method of calculating scaling factors based on the thermal expansion coefficient is used for temperature compensation calculations, the temperature compensation for large-sized measured objects is clearly inaccurate, amplifying the measurement deviation to some extent. Therefore, for the measurement of large assembly fixtures, it is necessary to consider the influence of anchor point positions and the different thermal expansion coefficients between different materials. Summary of the Invention

[0004] The purpose of this invention is to address the problem of excessive measurement errors in current large-scale assembly tooling measurements due to the failure of laser trackers to adequately consider relevant influencing factors when calculating the scaling factor based on the coefficient of thermal expansion. This invention provides a temperature compensation calculation method and apparatus for laser trackers used in tooling measurements. This method considers the differences in thermal expansion coefficients between anchor point positions, the main frame of the tooling, and the temperature compensation plate.

[0005] The first aspect of this invention provides a method for calculating temperature compensation using a laser tracker for tooling measurement. The tooling to be measured includes: a main frame and a temperature compensation plate; the method includes:

[0006] Step 1: Use a laser tracker to measure the coordinates of the calibration points and anchor points on the assembly fixture, and record the ambient temperature of this measurement; the anchor points include: the anchor point of the main frame relative to the foundation and the anchor point of the temperature compensation plate relative to the main frame; the calibration points are set on the temperature compensation plate;

[0007] Step 2: Under varying ambient temperature conditions, use a laser tracker again to measure the coordinates of the calibration point and anchor point, and record the ambient temperature of this measurement.

[0008] Step 3: Correct the coordinates from Step 2 using the following temperature compensation formula to eliminate thermal deformation caused by changes in ambient temperature.

[0009] u′=β(u+γ);

[0010] Where u is the coordinate of the calibration point after the temperature change, and the calibration point is any calibration point on the temperature compensation plate; u′ is the coordinate value of u after correction; The scaling factor; γ = α²ΔTu F2 +α1ΔT(u F1 -u F2 ) represents the compensation coefficient; α1 and α2 are the thermal expansion coefficients of the main frame and the temperature compensation plate, respectively; u F1 u F2 These are the coordinates of the main frame anchor point and the temperature compensation plate anchor point in step one, respectively; ΔT is the temperature difference between the two measurements.

[0011] Optionally, the laser tracker temperature compensation calculation method used for tooling measurement also includes:

[0012] Step four: Subtract the coordinates of the calibration point in step one from the corrected coordinates in step three to determine whether the measurement data is within the allowable error range.

[0013] Optionally, the calibration points are arranged along the length of the temperature compensation plate.

[0014] Optionally, the length of the temperature compensation plate shall not be less than 10 meters.

[0015] A second aspect of the present invention also provides a laser tracker temperature compensation calculation device for tooling measurement, wherein the tooling to be measured includes: a main frame and a temperature compensation plate; the device includes:

[0016] The first measurement module is used to measure the coordinates of the calibration points and anchor points on the assembly tooling using a laser tracker, and to record the ambient temperature of this measurement; the anchor points include: the anchor point of the main frame relative to the foundation and the anchor point of the temperature compensation plate relative to the main frame; the calibration points are set on the temperature compensation plate;

[0017] The second measurement module is used to measure the coordinates of the calibration point and anchor point again using a laser tracker when the ambient temperature changes, and at the same time record the ambient temperature of this measurement.

[0018] The correction module is used to correct the coordinates in the second measurement module using the following temperature compensation formula, thereby eliminating thermal deformation caused by changes in ambient temperature.

[0019] u′=β(u+γ);

[0020] Where u is the coordinate of the calibration point after the temperature change, and the calibration point is any calibration point on the temperature compensation plate; u′ is the coordinate value of u after correction; The scaling factor; γ = α²ΔTu F2 +α1ΔT(u F1 -u F2 ) represents the compensation coefficient; α1 and α2 are the thermal expansion coefficients of the main frame and the temperature compensation plate, respectively; u F1 u F2 These are the coordinates of the main frame anchor point and the temperature compensation plate anchor point in step one, respectively; ΔT is the temperature difference between the two measurements.

[0021] Optionally, the device further includes:

[0022] The judgment module is used to calculate the difference between the coordinates of the calibration point after correction and the coordinates before deformation, and to determine whether the measurement data is within the allowable error range.

[0023] A third aspect of the present invention provides a computer-readable storage medium, comprising: a memory and a processor;

[0024] The memory is configured to store executable instructions;

[0025] The processor is configured to implement the method as described in any one of the first aspects when executing the executable instructions stored in the memory.

[0026] A fourth aspect of the present invention provides a computer program product comprising instructions that, when executed by a computer, implement the method as described in any one of the first aspects.

[0027] The beneficial effects of this invention are as follows: Addressing the shortcomings of existing laser tracker temperature proportional compensation calculation methods in the measurement of large assembly fixtures, this invention proposes a laser tracker temperature compensation calculation method and apparatus for fixture measurement. This method fully considers the difference in thermal expansion coefficients between the temperature compensation plate and the main frame of the fixture, the anchor point position of the temperature compensation plate relative to the main frame, and the anchor point position of the main frame relative to the foundation. It is an effective and accurate laser tracker temperature compensation calculation method. The calculation method proposed in this invention can more accurately eliminate the influence of temperature changes on measurement data, and is better suited for the measurement of large assembly fixtures with temperature compensation plates, thereby more realistically reflecting assembly quality and improving the assembly production efficiency of large aircraft components. Furthermore, compared with existing laser tracker measurement procedures, this invention only requires the addition of anchor point measurement and the provision of thermal expansion coefficients for the temperature compensation plate and the main frame of the fixture during the measurement process, with almost no increase in the complexity of the operation process. Attached Figure Description

[0028] Figure 1 A schematic diagram of the thermal deformation structure for deriving the calculation method provided in this invention;

[0029] Figure 2 This is a schematic diagram of a large-scale frame assembly fixture provided in an embodiment of the present invention;

[0030] Figure 3 This is a comparison of the coordinates of the calibration point before deformation, after deformation, and after correction in an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0033] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0035] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0037] This invention provides a method and apparatus for calculating temperature compensation using a laser tracker for tooling measurement. The tooling structure under test includes a main frame, a temperature compensation plate, and several calibration points. The main frame has a sufficiently large dimension in at least one dimension to ensure that the effect of temperature changes on its deformation cannot be ignored. The temperature compensation calculation fully considers the differences in thermal expansion coefficients between the temperature compensation plate and the tooling in large assembly tooling, the anchoring positions of the temperature compensation plate relative to the main frame of the tooling, and the anchoring positions of the main frame of the tooling relative to the foundation.

[0038] In this invention, the main frame and the foundation are anchored at points, the temperature compensation plate is also anchored at points relative to the main structure, and the calibration point is attached to the temperature compensation plate.

[0039] This invention provides a method for calculating temperature compensation of a laser tracker for tooling measurement, the main steps of which include:

[0040] Step 1: Use a laser tracker to measure the coordinates of the calibration points and anchor points on the tooling of the large equipment, and record the ambient temperature of this measurement.

[0041] Step 2: Under varying ambient temperature conditions, use a laser tracker again to measure the coordinates of the calibration point and anchor point, and record the ambient temperature at the same time.

[0042] Step 3: Correct the coordinates from Step 2 using the following temperature compensation formula to eliminate thermal deformation caused by changes in ambient temperature.

[0043] u′=β(u+γ);

[0044] Where u is the coordinate of the calibration point after the temperature change, and the calibration point is any calibration point on the temperature compensation plate; u′ is the coordinate value of u after correction; The scaling factor; γ = α²ΔTu F2 +α1ΔT(u F1 -u F2 ) represents the compensation coefficient; α1 and α2 are the thermal expansion coefficients of the main frame and the temperature compensation plate, respectively; u F1 u F2 These are the coordinates of the main frame anchor point and the temperature compensation plate anchor point in step one, respectively; ΔT is the temperature difference between the two measurements.

[0045] Step four: Subtract the original coordinates from the corrected coordinates of the calibration point to determine whether the measurement data is within the allowable error range.

[0046] In this invention, step three considers not only the influence of the thermal expansion coefficient of different materials, but also the influence of the anchor point position.

[0047] In this invention, the influence of the anchor point position is reflected in the compensation coefficient γ=α2ΔTu F2 +α1ΔT(u F1 -u F2 )middle.

[0048] In this invention, the scaling factor in step three... It is only related to the coefficient of thermal expansion of the temperature compensation plate and the changing temperature.

[0049] This invention provides a method and apparatus for calculating temperature compensation in a laser tracker used for tooling measurement. The theoretical basis for its implementation is as follows: Figure 1 .

[0050] Figure 1 The structure includes plate 1 and plate 2, with thermal expansion coefficients of α1 and α2, respectively; plate 1 is anchored to the foundation, and the initial coordinates of the anchor point are u. F1 Plate 2 and plate 1 are anchored, and the initial coordinates of the anchor points are u. F2 The initial coordinates of the calibration point are u0. Assuming the temperature change is ΔT and the coordinates of the calibration point after thermal deformation are u, then:

[0051] u=u0+α1ΔT(u F2 -u F1 )+α2ΔT(u0-u F2 )

[0052] Right now:

[0053]

[0054] The above formula means that to eliminate the thermal deformation of the calibration point, the deformed coordinate u of the calibration point needs to be compensated by γ first, and then multiplied by the scaling factor β. In actual measurement, due to factors such as assembly stress and measurement errors, u after correction is usually not completely consistent with u0. Therefore, the correction formula for u should be written as:

[0055]

[0056] Based on this, this embodiment takes a typical enclosed frame-type large assembly fixture as the research object, such as... Figure 2 As shown, the feasibility and accuracy of the calculation method described in this invention are verified through finite element simulation, including the following steps:

[0057] Step 1: Establish a geometric model of the large-scale assembly tooling with a surrounding frame;

[0058] Step 2: Grid the data, set boundary conditions, and set the overall temperature change to 10°C.

[0059] Step 3: Extract the coordinates of the calibration points before and after deformation;

[0060] Step four: Correct the coordinates of the calibration point after deformation using the correction method proposed in this invention;

[0061] Step 5: Compare the corrected coordinates of the calibration point with the coordinates before and after deformation.

[0062] Figure 3The coordinates of the calibration point before deformation, after deformation, and after correction are shown. The results demonstrate that the temperature compensation calculation method proposed in this invention can effectively eliminate thermal deformation after deformation caused by temperature changes. The coordinates after eliminating the temperature effect are basically consistent with the initial coordinates, indicating that this invention has good feasibility and effectiveness.

[0063] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method for calculating temperature compensation in a laser tracker used for tooling measurement, characterized in that, The assembly fixture under test includes: a main frame and a temperature compensation plate; the method includes: Step 1: Use a laser tracker to measure the coordinates of the calibration points and anchor points on the assembly fixture, and record the ambient temperature of this measurement; the anchor points include: the anchor point of the main frame relative to the foundation and the anchor point of the temperature compensation plate relative to the main frame; the calibration points are set on the temperature compensation plate; Step 2: Under varying ambient temperature conditions, use a laser tracker again to measure the coordinates of the calibration point and anchor point, and record the ambient temperature of this measurement. Step 3: Correct the coordinates from Step 2 using the following temperature compensation formula to eliminate thermal deformation caused by changes in ambient temperature. u′=β(u+γ); Where u is the coordinate of the calibration point after the temperature change, and the calibration point is any calibration point on the temperature compensation plate; u′ is the coordinate value of u after correction; The scaling factor; γ = α²ΔTu F2 +α1ΔT(u F1 -u F2 ) represents the compensation coefficient; α1 and α2 are the thermal expansion coefficients of the main frame and the temperature compensation plate, respectively; u F1 u F2 These are the coordinates of the main frame anchor point and the temperature compensation plate anchor point in step one, respectively; ΔT is the temperature difference between the two measurements.

2. The method for calculating temperature compensation of a laser tracker for tooling measurement according to claim 1, characterized in that, Also includes: Step four: Subtract the coordinates of the calibration point in step one from the corrected coordinates in step three. The difference is used to determine whether the measurement data is within the allowable error range.

3. The method for calculating temperature compensation of a laser tracker for tooling measurement according to claim 1, characterized in that, The calibration points are arranged along the length of the temperature compensation plate.

4. The method for calculating temperature compensation of a laser tracker for tooling measurement according to claim 1, characterized in that, The length of the temperature compensation plate shall not be less than 10 meters.

5. A temperature compensation calculation device for a laser tracker used in tooling measurement, characterized in that, The fixture under test includes: a main frame and a temperature compensation plate; the device includes: The first measurement module is used to measure the coordinates of the calibration points and anchor points on the assembly tooling using a laser tracker, and to record the ambient temperature of this measurement; the anchor points include: the anchor point of the main frame relative to the foundation and the anchor point of the temperature compensation plate relative to the main frame; the calibration points are set on the temperature compensation plate; The second measurement module is used to measure the coordinates of the calibration point and anchor point again using a laser tracker when the ambient temperature changes, and at the same time record the ambient temperature of this measurement. The correction module is used to correct the coordinates in the second measurement module using the following temperature compensation formula, thereby eliminating thermal deformation caused by changes in ambient temperature. u′=β(u+γ); Where u is the coordinate of the calibration point after the temperature change, and the calibration point is any calibration point on the temperature compensation plate; u′ is the coordinate value of u after correction; The scaling factor; γ = α²ΔTu F2 +α1ΔT(u F1 -u F2 ) represents the compensation coefficient; α1 and α2 are the thermal expansion coefficients of the main frame and the temperature compensation plate, respectively; u F1 u F2 These are the coordinates of the main frame anchor point and the temperature compensation plate anchor point in step one, respectively; ΔT is the temperature difference between the two measurements.

6. The apparatus according to claim 5, characterized in that, Also includes: The judgment module is used to calculate the difference between the coordinates of the calibration point after correction and the coordinates before deformation, and to determine whether the measurement data is within the allowable error range.

7. A computer-readable storage medium, characterized in that, include: Memory and processor; The memory is configured to store executable instructions; The processor is configured to implement the method as described in any one of claims 1 to 4 when executing the executable instructions stored in the memory.

8. A computer program product, characterized in that, The computer program product includes instructions that, when executed by a computer, implement the method as described in any one of claims 1 to 4.

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