A method and system for measuring and calculating the coaxiality of a helicopter tail drive shaft

Abstract

This invention provides a method and system for measuring and calculating the coaxiality of a helicopter tail drive shaft. The method includes: selecting two cross-sections on a reference shaft segment, measuring the distance from a laser displacement sensor to the shaft segment surface, and simultaneously measuring the distance between the two cross-sections; selecting two cross-sections on a shaft segment under test, measuring the distance from a laser displacement sensor to the shaft segment surface, and simultaneously measuring the distance between the two cross-sections; preprocessing the measured data; reconstructing a coaxiality calculation model based on the preprocessing results; reconstructing a spatial geometric model of the tail drive shaft system based on the spatial geometric models of the reference shaft segment and the shaft segment under test, and calculating the coaxiality deviation between the reference shaft segment and the shaft segment under test; achieving high-precision coaxiality deviation calculation; and through real-time evaluation and feedback of the coaxiality calculation results, problems can be identified in a timely manner and adjustment suggestions can be given, realizing real-time monitoring and optimization of the helicopter tail drive shaft system and ensuring the safe operation of the helicopter.

Description

Technical Field

[0001] This invention belongs to the field of helicopter manufacturing and maintenance technology, and in particular relates to a method and system for measuring and calculating the coaxiality of a helicopter tail drive shaft. Background Technology

[0002] The tail rotor is a crucial component of a helicopter's power transmission system, responsible for transferring power from the engine to the tail rotor to ensure flight stability and controllability. The coaxiality of the tail rotor has a critical impact on the overall performance and reliability of the helicopter. Poor coaxiality can lead to additional vibration and noise during operation, accelerate component wear, reduce power transmission efficiency, and may even cause serious mechanical failures, threatening the helicopter's flight safety.

[0003] Existing methods for measuring the coaxiality of helicopter tail drive shafts have certain limitations. Some traditional methods rely heavily on manual measurement and experience, resulting in low accuracy and susceptibility to human factors, making it difficult to accurately reflect the actual coaxiality of the tail drive shaft. While some advanced optical measurement methods offer higher accuracy, they are expensive, complex to operate, require specialized technicians, and are significantly limited by the measurement environment in practical applications. Summary of the Invention

[0004] To address the problems of reliance on manual measurement and experience-based judgment in helicopter tail drive shaft coaxiality measurement, which results in low measurement accuracy and susceptibility to human factors, making it difficult to accurately reflect the actual coaxiality of the tail drive shaft; and the high cost and complex operation of the equipment, this invention provides a method and system for measuring and calculating the coaxiality of helicopter tail drive shafts. This method can be used to accurately assess the coaxiality of helicopter tail drive shafts, providing strong support for safe helicopter operation and performance optimization. The technical solution is as follows:

[0005] Firstly, a method for measuring and calculating the coaxiality of a helicopter tail drive shaft is provided, including:

[0006] Step 1: Select two first cross-sections on the reference shaft segment, measure the distance from the laser displacement sensor to the surface of the reference shaft segment, obtain two sets of reference shaft segment data, and simultaneously measure the distance between the two first cross-sections; Select two second cross-sections on the shaft segment to be measured, measure the distance from the laser displacement sensor to the surface of the shaft segment to be measured, obtain two sets of shaft segment data, and simultaneously measure the distance between the two second cross-sections;

[0007] Step 2: Preprocess the data measured in Step 1. The preprocessing includes filtering, calibration, and fitting.

[0008] Step 3: Reconstruct the coaxiality calculation model based on the preprocessing results of Step 2. The coaxiality calculation model includes the spatial geometric model of the reference shaft segment and the spatial geometric model of the shaft segment under test.

[0009] Step 4: Reconstruct the spatial geometric model of the tail drive shaft system based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment, and calculate the angle adjustment and spatial offset of the reference shaft segment and the measured shaft segment in the spatial geometric model of the tail drive shaft system to obtain the coaxiality deviation of the reference shaft segment and the measured shaft segment. The coaxiality deviation includes spatial angle deviation and distance deviation.

[0010] In step 1, when measuring data, the laser displacement sensor is installed on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail and also move along the linear guide rail of the support and positioning system with the annular guide rail. The support and positioning system includes a bracket, an annular guide rail, and a linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is installed on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft with the slider on the linear guide rail. The bracket is fixed by a locking nut.

[0011] Optionally, in step 2,

[0012] When filtering the acquired data, the Kalman tracking filter is used to perform adaptive mean filtering to remove outliers and noise, resulting in better consistency between adjacent data points.

[0013] During calibration, the filtered data is calibrated according to the calibration parameters of the laser displacement sensor to eliminate the measurement error of the laser displacement sensor. Zero-point calibration is performed on the data, with the initial position of the shaft segment as the zero point, to ensure the accuracy of the measurement data.

[0014] During the fitting process, the complete shape of the cross-section is fitted based on the filtered data. If the annular guide rail and the tail drive shaft axis are completely perpendicular, the fitted cross-section is a complete circle; if the annular guide rail and the tail drive shaft axis are not completely perpendicular, the fitted cross-section is an ellipse.

[0015] Optionally, step 3 includes:

[0016] Establish an absolute coordinate system: Take the center of the circular guide rail near the support end as the origin of the coordinate system and establish an absolute coordinate system. The X-axis of the absolute coordinate system is parallel to the linear guide rail, the Y-axis is perpendicular to the X-axis, and the Z-axis direction is determined according to the right-hand rule.

[0017] Establish a spatial geometric model of the reference shaft segment: Reconstruct the spatial geometric model of the reference shaft segment based on the cross section on the reference shaft and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the reference shaft segment include the radius of the reference shaft segment, the spatial coordinates (x1, y1, z1) on the axis, and the angles α1, β1, and γ1 between the axis and the X, Y, and Z directions in the absolute coordinate system.

[0018] Establish the spatial geometric model of the measured shaft segment: The spatial geometric model of the measured shaft segment is reconstructed based on the cross section of the measured shaft segment and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the measured shaft segment include the radius of the measured shaft segment, the spatial coordinates (x2, y2, z2) on the axis, and the angles α2, β2, and γ2 between the axis and the X, Y, and Z directions in the absolute coordinate system.

[0019] Optionally, step 4 includes:

[0020] The spatial geometric model of the tail drive shaft system is reconstructed based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment using the third-order linear extrapolation fitting method; the spatial geometric model curve of the tail drive shaft system can be fitted using the third-order linear extrapolation fitting method.

[0021] Based on the radius of the reference axis segment, the spatial coordinates (x1, y1, z1) on the axis centerline, and the included angles α1, β1, γ1, and the radius of the measured axis segment, the spatial coordinates (x2, y2, z2) on the axis centerline, and the included angles α2, β2, γ2, the angular adjustment amounts θ, φ, Ω and spatial offsets δ, η, ζ of the reference axis segment and the measured axis segment, as well as the spatial angular deviation Ψ and distance deviation ε of the coaxiality deviation between the reference axis segment and the measured axis segment, are calculated, and adjustment suggestions are given. The adjustment suggestions are: adjust the position of the measured axis according to the calculated angular adjustment amounts θ, φ, Ω and spatial offsets δ, η, ζ, as well as the spatial angular deviation Ψ and distance deviation ε.

[0022] Wherein, the included angles θ, φ, and Ω are the spatial deviation angles between the measured axis centerline and the reference axis centerline, the rotation axis of θ is the x-line of the reference axis centerline, the rotation axis of φ is the y-line of the reference axis centerline, and the rotation axis of Ω is the z-line of the reference axis centerline; the spatial offsets δ, η, and ζ are the parallelism deviations between the measured axis centerline and the reference axis centerline, δ is the offset in the x-direction relative to the reference axis, η is the offset in the y-direction relative to the reference axis, and ζ is the offset in the z-direction relative to the reference axis.

[0023] The spatial angle deviation Ψ is the angle between the reference axis and the measured axis. The angle between two straight lines in space is defined as the minimum angle between the direction vectors of the two straight lines, and its value ranges from 0 to 90°.

[0024] The distance deviation ε is the spatial distance between the reference axis and the measured axis. It is a scalar quantity and has no measurement direction.

[0025] Optionally, the formulas for calculating the angular adjustment amounts θ, φ, Ω between the reference axis segment and the measured axis segment, and the spatial offsets δ, η, ζ are as follows:

[0026] θ=α1-α2, φ=β1-β2, Ω=γ1-γ2,

[0027] δ=x1-x2, η=y1-y2, ζ=z1-z2,

[0028] The formulas for calculating spatial angular deviation Ψ and distance deviation ε are:

[0029] Ψ=arcos(|cosα1 / cosα2+ cosβ1 / cosβ2+ cosγ1 / cosγ2|),

[0030] ε=|(x1-x2)*(cosβ1*cosγ2-cosγ1*cosβ2)+(y1-y2)*( cosα1*cosγ2-cosγ1*cosα2)+(z1-z2)*(cosα1*cosβ2+ cosβ1*cosα2)|.

[0031] Furthermore, the method also includes:

[0032] If the direction cosines of the two axes satisfy the proportionality condition, the two axes are determined to be parallel. If the two axes are parallel, it is determined whether the two axes coincide. If the two axes coincide, an adjustment suggestion is given, which means that there is no need to adjust the position of the measured axis and the coaxiality of the two axes is qualified. The proportionality condition is cosα1 / cosα2=cosβ1 / cosβ2=cosγ1 / cosγ2.

[0033] If the two axes are not parallel, proceed to step 4.

[0034] Optionally, calculate whether there exists a unique real number m such that the three equations x1=x2+m*cosα2, y1=y2+m*cosβ2, and z1=z2+m*cosγ2 are all true. If so, then determine that the two axes coincide.

[0035] Secondly, a system for measuring and calculating the coaxiality of a helicopter tail drive shaft is provided, including: a laser displacement sensor and a processor.

[0036] The processor is used to preprocess the data measured by the laser displacement sensor and the cross-sectional distance data, calculate the angular adjustment and spatial offset between the reference shaft segment and the measured shaft segment, as well as the coaxiality deviation between the reference shaft segment and the measured shaft segment, wherein the coaxiality deviation includes spatial angular deviation and distance deviation.

[0037] The laser displacement sensor is installed on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail and can also move along the linear guide rail of the support and positioning system with the annular guide rail. The support and positioning system includes a bracket, an annular guide rail, and a linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is installed on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft with the slider on the linear guide rail. The bracket is fixed by a locking nut.

[0038] The beneficial effects of this application are at least as follows:

[0039] 1. High calculation accuracy: Data is acquired using a high-precision laser displacement sensor, combined with adaptive filtering and calibration techniques, effectively improving the accuracy and reliability of the data. Simultaneously, by establishing a precise coaxiality calculation model, high-precision coaxiality deviation calculation is achieved.

[0040] 2. Low cost: The laser displacement sensor and support and positioning system used are relatively inexpensive, and the calculation process is simple and easy to implement.

[0041] 3. High practicality: It can adapt to the coaxiality calculation of the helicopter tail drive shaft under different operating conditions, and has good versatility and adaptability.

[0042] 4. Real-time feedback and adjustment: Through real-time evaluation and feedback of coaxiality calculation results, problems can be identified in a timely manner and adjustment suggestions can be given, realizing real-time monitoring and optimization of the helicopter tail drive shaft system, and ensuring the safe operation of the helicopter. Attached Figure Description

[0043] Figure 1 A schematic diagram of the support and positioning system;

[0044] Figure 2 This is a schematic diagram of the fitted cross section when the annular guide rail is completely perpendicular to the tail drive shaft axis;

[0045] Figure 3 This is a schematic diagram of the fitted cross section when the annular guide rail and the tail drive shaft axis are not completely perpendicular;

[0046] Figure 4 This is a schematic diagram of the spatial relationship between the reference shaft segment and the shaft segment being measured. Detailed Implementation

[0047] 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.

[0048] 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.

[0049] 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 from each other.

[0050] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0051] An embodiment of the present invention provides a method for measuring and calculating the coaxiality of a helicopter tail drive shaft, comprising the following steps:

[0052] 1. Data collection

[0053] See Figure 1 The support and positioning system consists of two sets of height- and angle-adjustable brackets, a ring guide rail, a linear guide rail, and locking nuts. The brackets are made of high-strength aluminum alloy, providing stable and reliable support for the ring guide rail and laser displacement sensor. The brackets are installed across the axis, ensuring the bracket plane is perpendicular to the tail drive shaft axis, and are securely fixed with locking nuts. The linear guide rail is mounted on the bracket along the tail drive shaft axis. The ring guide rail is fixed to the slider of the linear guide rail and can move axially along the tail drive shaft along the linear guide rail with the slider.

[0054] In one embodiment, the support and positioning system may also be replaced by a robotic arm with a movable base.

[0055] See Figure 1When arranging the laser displacement sensor, the laser displacement sensor is installed on the circular guide rail. The laser displacement sensor can rotate circumferentially along the circular guide rail, or it can move along the linear guide rail with the circular guide rail.

[0056] See Figure 4 On the one hand, two first cross sections are selected on the reference shaft segment, and the distance from the laser displacement sensor to the surface of the reference shaft segment is measured to obtain two sets of reference shaft segment data, while the distance between the two first cross sections is measured at the same time; on the other hand, two second cross sections are selected on the shaft segment to be measured, and the distance from the laser displacement sensor to the surface of the shaft segment to be measured is measured to obtain two sets of shaft segment data, while the distance between the two second cross sections is measured at the same time.

[0057] 2. Data Preprocessing

[0058] Data filtering: Adaptive mean filtering is applied to a single set of data, such as Kalman tracking filtering and LMS filtering, to remove outliers and noise, resulting in better consistency between adjacent data points.

[0059] Data calibration: Based on the calibration parameters of the laser displacement sensor, the filtered data is calibrated to eliminate measurement errors from the laser displacement sensor. Simultaneously, zero-point calibration is performed on the data, using the initial position of the shaft segment as the zero point, to ensure the accuracy of the measurement data.

[0060] Data Fitting: Based on the filtered data, fit the complete shape of the cross-section. If the annular guide rail is perfectly perpendicular to the tail drive shaft axis, the fitted cross-section will be a complete circle, see... Figure 2 If the annular guide rail is not perfectly perpendicular to the tail drive shaft axis, the fitted cross-section will be an ellipse, see... Figure 3 .

[0061] 3. Reconstruct the coaxiality calculation model

[0062] 31. Establish an absolute coordinate system: Take the center of the circular guide rail near the support end as the origin and establish an absolute coordinate system. The X-axis of this absolute coordinate system is parallel to the linear guide rail, and the Y-axis is perpendicular to the X-axis. Determine the direction of the Z-axis according to the right-hand rule.

[0063] 32. Establish the spatial geometric model of the reference shaft segment: Reconstruct the spatial geometric model of the reference shaft segment based on the cross section on the reference shaft and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the reference shaft segment include the radius of the reference shaft segment, the spatial coordinates (x1, y1, z1) on the axis, and the angles α1, β1, and γ1 between the axis and the X, Y, and Z directions in the absolute coordinate system.

[0064] 33. Establish the spatial geometric model of the measured shaft segment: Reconstruct the spatial geometric model of the measured shaft segment based on the cross section of the measured shaft segment and the axial sliding distance of the laser displacement sensor. The parameters in the spatial geometric model of the measured shaft segment include the radius of the measured shaft segment, the spatial coordinates (x2, y2, z2) on the axis, and the angles α2, β2, and γ2 between the axis and the X, Y, and Z directions in the absolute coordinate system.

[0065] The direction cosines can be directly calculated based on the direction angles. The direction cosines of the reference axis are: cosα1, cosβ1, cosγ1, and the direction cosines of the measured axis are: cosα2, cosβ2, cosγ2. The calculation then checks if the following condition is met: (cosα1) 2 +(cosβ1) 2 +(cosγ1) 2 =1, (cosα2) 2 +(cosβ2) 2 +(cosγ2) 2 =1, to ensure the measurement is accurate.

[0066] 4. If the direction cosines of the two axes satisfy the proportionality condition, the two axes are determined to be parallel. If the two axes are parallel, determine whether the two axes coincide. If the two axes coincide, then no adjustment is required: there is no need to adjust the position of the measured axis, and the coaxiality of the two axes is qualified.

[0067] The proportionality condition is cosα1 / cosα2=cosβ1 / cosβ2=cosγ1 / cosγ2.

[0068] If the two axes are not parallel, calculate the coaxiality deviation.

[0069] In one feasible approach, when determining whether two axes coincide, it is calculated whether there exists a unique real number m such that the three equations x1=x2+m*cosα2, y1=y2+m*cosβ2, and z1=z2+m*cosγ2 are all true. If so, the two axes are determined to coincide.

[0070] 5. Calculate coaxiality: If the two shafts are not parallel, reconstruct the spatial geometric model of the tail drive shaft system based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment, calculate the coaxiality deviation between the reference shaft segment and the measured shaft segment in the spatial geometric model of the tail drive shaft system, and provide adjustment suggestions.

[0071] 51. Model Input: Import the reconstructed spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment into the calculation program. Reconstruct the spatial geometric model of the tail drive shaft system using an interpolation fitting algorithm. A third-order linear extrapolation fitting method can be used to fit the curve. Refer to relevant technologies for details.

[0072] 52. Based on the radius of the reference shaft segment, the spatial coordinates (x1, y1, z1) on the axis, and the included angles α1, β1, γ1, and the radius of the measured shaft segment, the spatial coordinates (x2, y2, z2) on the axis, and the included angles α2, β2, γ2, calculate the angular adjustment amounts θ, φ, Ω and spatial offsets δ, η, ζ between the reference shaft segment and the measured shaft segment, as well as the spatial angular deviation Ψ and distance deviation ε of the coaxiality deviation between the reference shaft segment and the measured shaft segment. The included angles θ, φ, and Ω are the spatial deviation angles between the measured axis centerline and the reference axis centerline. The rotation axis of θ is the x-line of the reference axis centerline, the rotation axis of φ is the y-line of the reference axis centerline, and the rotation axis of Ω is the z-line of the reference axis centerline. The spatial offsets δ, η, and ζ are the parallelism deviations between the measured axis centerline and the reference axis centerline. δ is the offset in the x-direction relative to the reference axis, η is the offset in the y-direction relative to the reference axis, and ζ is the offset in the z-direction relative to the reference axis.

[0073] The spatial angle deviation Ψ is the angle between the reference axis and the measured axis. The angle between two straight lines in space is defined as the minimum angle between the direction vectors of the two straight lines, and its value ranges from 0 to 90°.

[0074] The distance deviation ε is the spatial distance between the reference axis and the measured axis. It is a scalar quantity and has no measurement direction.

[0075] The formulas for calculating the angle adjustment amounts θ, φ, Ω between the reference axis segment and the measured axis segment, and the spatial offset amounts δ, η, ζ are as follows:

[0076] θ=α1-α2, φ=β1-β2, Ω=γ1-γ2,

[0077] δ=x1-x2, η=y1-y2, ζ=z1-z2,

[0078] The formulas for calculating spatial angular deviation Ψ and distance deviation ε are:

[0079] Ψ=arcos(|cosα1 / cosα2+ cosβ1 / cosβ2+ cosγ1 / cosγ2|),

[0080] ε=|(x1-x2)*(cosβ1*cosγ2-cosγ1*cosβ2)+(y1-y2)*( cosα1*cosγ2-cosγ1*cosα2)+(z1-z2)*(cosα1*cosβ2+ cosβ1*cosα2)|.

[0081] 53. Provide adjustment suggestions: Adjust the position of the measured axis according to the calculated angle adjustment amounts θ, φ, Ω and spatial offsets δ, η, ζ, as well as the spatial angle deviation Ψ and distance deviation ε.

[0082] It should be added that if the two axes are parallel but do not coincide, coaxiality deviation calculation is also performed. In this case, the angle adjustment and spatial offset of the reference axis segment and the measured axis segment are both zero.

[0083] This invention establishes an absolute coordinate system with the center of the circular guide rail near the support end as the origin. Two cross-sections of the reference shaft segment are selected as references. The spatial data of the measured cross-section circle is obtained by measuring the distance from the laser measuring instrument to the shaft surface, and the spatial coordinates of the reference shaft are established. Two cross-sections of the measured shaft segment are selected, and the cross-section circle is measured to establish the spatial coordinates of the measured shaft. Signal processing methods are used to eliminate measurement errors and fit the most realistic cross-section circle. Based on the positional relationship between the reference shaft and the measured shaft in the spatial coordinates, the coaxiality relationship between the two axes is calculated, and a corresponding adjustment strategy is given.

[0084] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A method for measuring and calculating the coaxiality of a helicopter tail drive shaft, characterized in that, include: Step 1: Select two first cross-sections on the reference shaft segment, measure the distance from the laser displacement sensor to the surface of the reference shaft segment, obtain two sets of reference shaft segment data, and simultaneously measure the distance between the two first cross-sections; Select two second cross-sections on the shaft segment to be measured, measure the distance from the laser displacement sensor to the surface of the shaft segment to be measured, obtain two sets of shaft segment data, and simultaneously measure the distance between the two second cross-sections; Step 2: Preprocess the data measured in Step 1. The preprocessing includes filtering, calibration, and fitting. Step 3: Reconstruct the coaxiality calculation model based on the preprocessing results of Step 2. The coaxiality calculation model includes the spatial geometric model of the reference shaft segment and the spatial geometric model of the shaft segment under test. Step 4: Reconstruct the spatial geometric model of the tail drive shaft system, and calculate the angle adjustment and spatial offset of the reference shaft segment and the measured shaft segment, as well as the coaxiality deviation of the reference shaft segment and the measured shaft segment in the spatial geometric model of the tail drive shaft system. The coaxiality deviation includes spatial angle deviation and distance deviation. The parameters in the spatial geometric model of the reference axis segment include the radius of the reference axis segment, the spatial coordinates (x1, y1, z1) on the axis centerline, and the angles α1, β1, and γ1 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system; the parameters in the spatial geometric model of the measured axis segment include the radius of the measured axis segment, the spatial coordinates (x2, y2, z2) on the axis centerline, and the angles α2, β2, and γ2 between the axis centerline and the X, Y, and Z directions in the absolute coordinate system. The angle adjustment amounts between the reference axis segment and the measured axis segment are θ, φ, and Ω. The rotation axis of θ is the x-line of the reference axis centerline, the rotation axis of φ is the y-line of the reference axis centerline, and the rotation axis of Ω is the z-line of the reference axis centerline. The spatial offsets δ, η, and ζ are the parallelism deviations between the measured axis centerline and the reference axis centerline. δ is the offset in the x-direction relative to the reference axis, η is the offset in the y-direction relative to the reference axis, and ζ is the offset in the z-direction relative to the reference axis. θ=α1-α2, φ=β1-β2, Ω=γ1-γ2, δ=x1-x2, η=y1-y2, ζ=z1-z2, Ψ=arcos(|cosα1 / cosα2+cosβ1 / cosβ2+cosγ1 / cosγ2|), ε=|(x1-x2)*(cosβ1*cosγ2-cosγ1*cosβ2)+(y1-y2)*(cosα1*cosγ2-cosγ1*cosα2)+(z1-z2)*(cosα1*cosβ2+cosβ1*cosα2)|; The method further includes: if the direction cosines of the two axes satisfy the proportionality condition, determining that the two axes are parallel; if the two axes are parallel, determining whether the two axes coincide; if the two axes coincide, giving a no-adjustment suggestion, wherein the no-adjustment suggestion means: no adjustment is needed to the position of the measured axis, and the coaxiality of the two axes is qualified; the proportionality condition is... ; Determine if there exists a unique real number m such that , , If all three equations are true, then the two axes are considered to coincide.

2. The method according to claim 1, characterized in that, If the two axes are not parallel, proceed to step 4.

3. The method according to claim 1, characterized in that, When measuring data in step 1, the laser displacement sensor is installed on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail and also move along the linear guide rail of the support and positioning system with the annular guide rail. The support and positioning system includes a bracket, an annular guide rail, and a linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is installed on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft with the slider on the linear guide rail. The bracket is fixed by a locking nut.

4. The method according to claim 1, characterized in that, In step 2, When filtering the acquired data, adaptive mean filtering is performed to remove outliers and noise, resulting in better consistency between adjacent data points. During calibration, the filtered data is calibrated according to the calibration parameters of the laser displacement sensor to eliminate the measurement error of the laser displacement sensor. The data is then zeroed, with the initial position of the shaft segment as the zero point, to ensure the accuracy of the measurement data. During the fitting process, the complete shape of the cross-section is fitted based on the filtered data. If the annular guide rail and the tail drive shaft axis are completely perpendicular, the fitted cross-section is a complete circle; if the annular guide rail and the tail drive shaft axis are not completely perpendicular, the fitted cross-section is an ellipse.

5. The method according to claim 1, characterized in that, In step 3, Establish an absolute coordinate system: Take the center of the circular guide rail near the support end as the origin of the coordinate system and establish an absolute coordinate system. The X-axis of the absolute coordinate system is parallel to the linear guide rail, the Y-axis is perpendicular to the X-axis, and the Z-axis direction is determined according to the right-hand rule. Establish the spatial geometric model of the reference shaft segment: reconstruct the spatial geometric model of the reference shaft segment based on the cross section on the reference shaft and the axial sliding distance of the laser displacement sensor; Establish the spatial geometric model of the measured shaft segment: reconstruct the spatial geometric model of the measured shaft segment based on the cross section of the measured shaft segment and the axial sliding distance of the laser displacement sensor.

6. The method according to claim 1, characterized in that, In step 4, The spatial geometric model of the tail drive shaft system is reconstructed based on the spatial geometric model of the reference shaft segment and the spatial geometric model of the measured shaft segment using an interpolation fitting algorithm. An adjustment suggestion is given, which is to adjust the position of the measured axis according to the calculated angle adjustment amounts θ, φ, Ω and spatial offsets δ, η, ζ, as well as the spatial angle deviation Ψ and distance deviation ε.

7. A system for measuring and calculating the coaxiality of a helicopter tail drive shaft, characterized in that, The system for measuring and calculating the coaxiality of the helicopter tail drive shaft according to any one of claims 1 to 6 includes: a laser displacement sensor and a processor. The processor is used to preprocess the data measured by the laser displacement sensor and the cross-sectional distance data, calculate the angular adjustment and spatial offset between the reference shaft segment and the measured shaft segment, as well as the coaxiality deviation between the reference shaft segment and the measured shaft segment, wherein the coaxiality deviation includes spatial angular deviation and distance deviation.

8. The system according to claim 7, characterized in that, The laser displacement sensor is mounted on the annular guide rail of the support and positioning system. The laser displacement sensor can rotate circumferentially along the annular guide rail and can also move along the linear guide rail of the support and positioning system with the annular guide rail. The support and positioning system includes a bracket, an annular guide rail, and a linear guide rail. The plane of the bracket is perpendicular to the axis of the tail drive shaft. The linear guide rail is mounted on the bracket along the axial direction of the tail drive shaft. The annular guide rail is fixed on the slider of the linear guide rail and can move along the axial direction of the tail drive shaft with the slider on the linear guide rail. The bracket is fixed by a locking nut.

Images