CN115682989A - Six-point positioning-based shape surface measuring method for turbine blade - Google Patents
Six-point positioning-based shape surface measuring method for turbine blade Download PDFInfo
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Abstract
The invention discloses a surface measuring method of a turbine blade based on six-point positioning, and relates to the technical field of measurement and testing; the method comprises the following steps: (S1) placing the turbine blade on a linear displacement table, and manually modulating a CMOS camera and a test facer to align the cross section and the surface of the turbine blade; (S2) measuring the contour line of the cross section of the other part of the turbine blade by testing the linear scanning of the faceting machine; (S3) the Renishaw PH10T measuring probe picks up three points to form an X-Y-Z coordinate system, the Renishaw PH10T measuring probe carries out six-point positioning on the turbine blade, and an SA-LM hybrid optimization surface measurement algorithm is adopted to optimize the measured surface parameters; (S4) creating a 3D CAD model of the turbine blade using the Pro/ENGINEER software package, with the shape parameters as input data to the computer system, with the normal vectors of the measurement points being generated by the computer system, and with the generated data being derived from the display of the computer system in DMIS format to create a simulation map; the method greatly improves the precision of the shape and the size of the turbine blade.
Description
Technical Field
The invention relates to the technical field of measurement and testing, in particular to a six-point positioning-based profile measuring method for a turbine blade.
Background
Turbine blades are important components of the turbine section of a gas turbine engine. The blades rotating at high speed are responsible for sucking high-temperature and high-pressure airflow into the combustor to maintain the operation of the engine. In order to ensure stable and long-term operation in extreme environments of high temperature and high pressure, turbine blades are often forged from high temperature alloys and are cooled in different ways, such as internal air flow cooling, boundary layer cooling, or thermal barrier coatings protecting the blades, to ensure operational reliability. In steam turbine engines and gas turbine engines, metal fatigue of the blades is the leading cause of engine failure. Strong vibration or resonance can lead to metal fatigue. Engineers often employ friction dampers to reduce damage to the blades from these factors. The blades may be divided into three types in particular embodiments, fan blades, compressor blades, and turbine blades. There are several different manufacturing processes for these types of blades, such as plunge, forging, and investment casting. The accuracy of the manufacture of these blades directly affects the performance, efficiency and life of the aircraft engine. In addition, with the development of high-performance aircraft engines, blades have the characteristics of complex structure, small tolerance, high precision and the like. Regardless of the manner in which the blades are manufactured, inspection is required to ensure the geometric accuracy of the blades. The blade is particularly difficult to measure because it consists of a complex free-form surface. Conventional blade profile inspection requires highly skilled technicians to use a large number of templates. The measurement speed is low and the accuracy is low. However, with the development of modern digital equipment, some efficient and accurate intelligent measuring devices for the profile of the turbine blade are available at the front and become main tools for profile verification in the manufacture of the turbine blade, and the intelligent measuring devices are driven by a measuring arm through a probe to move in X, Y and the Z direction, while a blade is fixed on a customized clamp. After the measurement surface is determined, the measurement points need to be sampled with a certain accuracy. And finally, generating a measuring path and finishing the blade profile measurement. Since the measurement is performed point by point, this is a rather complicated problem, and especially the measurement of the free-form surface becomes a technical problem to be solved. In the aspect of surface measurement, many researchers are dedicated to research on a measurement point sampling strategy on a free curved surface, wherein patent CN102867332B discloses a complex boundary constraint multistage subdivision grid surface fitting method, the method adopts a two-dimensional rectangular grid to define turbine blade measurement points on a curved surface, then grid points are projected onto the curved surface, each intersection point between a projection line and a model designates a turbine blade measurement point, and a constraint boundary is projected on a horizon surface subdivision grid by generating the two-dimensional rectangular grid; interpolation of horizon surface grid points; although the method is suitable for a solution of space surface fitting, the turbine blade is relatively small in application range based on six-point positioning, and the application process is complex.
Also, this method has a disadvantage in that it is not suitable for a turbine blade of a complicated shape having a high curvature. In order to overcome the problem, patent CN110057337B discloses an intelligent sampling method for free-form surface inspection, in the disclosed technical scheme, points are distributed in a curved surface in two steps: (1) Sampling the most critical points that depend on the maximum and minimum gaussian curvatures of each patch; (2) Adding more points depends on the overall distribution of the most critical points distributed on the surface. However, this intelligent sampling method cannot obtain a high-precision point when determining the design coordinate system of the part.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a six-point positioning-based profile measuring method for a turbine blade, which realizes the measurement of the surface shape of the turbine blade, realizes the high-precision performance of the shape and the size of the turbine blade machined by a self-adaptive adjusting device by positioning the actual shape of the turbine blade through a machine measuring method and comparing the actual shape with the nominal shape, and greatly improves the measuring capability and the measuring precision.
In order to achieve the purpose, the invention provides the following technical scheme:
a six-point positioning-based profile measurement method for a turbine blade comprises the following steps:
(S1) placing the turbine blade on a linear displacement table, and manually modulating a CMOS camera and a test facer to align the cross section and the surface of the turbine blade;
(S2) projecting a structured line laser pattern onto one surface of the turbine blade to be tested, capturing an image of the contour line of the turbine blade by a CMOS camera and preprocessing the image, and measuring the contour line of the cross section of the other part of the turbine blade by testing the linear scanning of the faceting machine;
(S3) the Renishaw PH10T measuring probe picks up three points to form an X-Y plane, then two points are taken to define an X axis, and a rotating shaft of a turbine blade center hole is obtained to place a Z axis; the Renishaw PH10T measuring probe carries out six-point positioning on the turbine blade, and optimizes the measured profile parameters by adopting an SA-LM hybrid optimization profile measuring algorithm;
(S4) creating a 3D CAD model of the turbine blade using the Pro/ENGINEER software package, with the profile parameters as input data to the computer system, with the normal vectors to the measurement points being generated by the computer system, and with the generated data being derived from the display of the computer system in DMIS format to create a simulation map.
As a further aspect of the invention, the six point locations are a leading edge point, a trailing edge point, a pressure side point, a suction side point, a large twist point, and a large camber point of the turbine blade.
As a further technical solution of the present invention, the CMOS camera is based on the projection of the laser line on the reference plane, the height variation in the profile of the turbine blade is measured by the lateral displacement of the point in the line projected on the measured object, the turbine blade is placed on a linear displacement table perpendicular to the Z axis, the minimum displacement measurable by the CMOS camera is of the order of 1 pixel assuming the coordinates of each point (X, Y, Z) of the projected laser line, the measurement sensitivity Δ of the CMOS camera is of the order of 1 pixelzObtained from equation (1):
in the formula (1), the reaction mixture is,a、band
are respectively provided withRepresenting the CMOS camera lens focal length, pinhole reference plane distance and viewing angle, deltaxRepresenting the amount of lateral displacement of the reference ray produced by the height variation over the selected contour along the projection line.
As a further technical scheme of the invention, the surface of the turbine blade needs to rotate continuously, the stepping motor of the Applied Motion Products is used for driving, and the control is carried out through an Arduino Mega 2560 micro control card.
As a further technical solution of the present invention, the contour line of the cross section is fitted by using the leading edge point of each section curve, and the trailing edge curve is fitted by using the trailing edge point of each section curve; the section curve of the blade is represented by non-uniform rational B splines and a node sequenceU={uOn (c) }kRational B-spline curve of orderCWith the parameter representation:
in the formula (2), the reaction mixture is,d i it is shown that the control point is,ithe sequence number is shown to indicate that,w i the weight is represented by a weight that is,Nrepresenting a B spline basis function on the node sequence U; fitting a leading edge curve by using a leading edge point of each section curve, fitting a trailing edge curve by using a trailing edge point of each section curve, sampling the leading edge curve and the trailing edge curve, setting L and T as sampling point sets of the leading edge curve and the trailing edge curve, respectively, and projecting L 'and T' on a blade stacking axis, wherein L 'is a projection point set corresponding to L and T' is a projection point set corresponding to T; for thePEach point in (1) throughD=||p 1 -p 2 I calculate the distance if D<2R, wherein R is the probe radius, thenP＝{p' i Is the final sampling point set, the section curve height can be from p' i Is expressed in terms of z-axis values.
As a further technical scheme of the invention, the plane of the turbine blade to be measured, which is arranged at the blade shroud, in the turbine blade is one of the sawtooth surfaces, and after the blank of the turbine blade is polished by the sawtooth surfaces, the precision of the sawtooth surfaces is measured to determine that the pretreatment process is carried out on the plane of the turbine blade.
As a further aspect of the invention, the calculation of the angular parameter between the measurement probe and the turbine blade assumes thatdIs the angle between two adjacent blades and is,
from the X axis to a passing measurement point P (P) x ，P y ，P z ) Is rotated about an axis of the shaft,
is the angle at which the current measurement point rotates around the Z axis until the next blade is contacted, the three angles can be formulated as:
in the formula (3), the reaction mixture is,nis the total number of blades, angle of rotation
The expression is as follows:
in the formula (4), the reaction mixture is,uis a pointPSince the turbine blade is composed of a pressure surface and a suction surface, as shown in fig. 1, in calculating the rotation angle δ to avoid collision between the probe and the turbine blade, it is necessary to consider the surface on which the measurement point is located, and the angle of the measurement point on the pressure surface satisfies formula (5):
the angle satisfies formula (6) for a measurement point located on the suction surface:
in equations (5) and (6), the stylus is rotated by an angle δ such that the stylus is in the middle of the safety boundary, i.e. the angle between the stylus and either of the two safety boundaries is y/2, and the stylus must be rotated for each point to be measured whether or not a collision occurs.
As a further technical scheme of the invention, the SA-LM hybrid optimization shape surface measurement algorithm process comprises the following steps:
the measuring probe measures the turbine blade in different postures, and the true value of the measuring point is the average value of the multiple measuring data: (x 0 , y 0 , z 0 ) Then the average value of the errors at the measurement points is:
in the formula (7), the reaction mixture is,ethe average value of the errors of the measurement points is represented,e i an error of the measured point is represented,ithe sequence number is shown to indicate that,nrepresents the number of measurement points; the standard deviation of the measurement points was calculated as:
in the formula (8), the reaction mixture is,
and the standard deviation of the measuring points is represented, and the overall measuring precision objective function of the measuring probe is as follows:
in the formula (9), OA represents a measurement objective function, and whether the turbine blade profile parameter calculated by the measuring probe is close to a true value is judged according to the value of the objective function; the calculation by using a least square method can obtain:
in the formula (10), ΔSWhich represents a vector of error parameters that is,Jrepresenting the Jacobian matrix, ΔMRepresenting a measured coordinate error model; transformation analysis was performed on the left side of the equation for the error model Δ S:
let K = (J) in formula (11) T ×J) -1 And carrying out singular value decomposition to obtain:
in the formula (12), the reaction mixture is,PandQfor orthogonal matrix, the matrix K is substituted back to equation (12) to obtain:
according to the matrix analysis in the formula (13), the profile parameters are known to have 6-rThe parameters have linear relation, r is the rank of the matrix, willQ T Middle and later 6-rThe row part is subjected to primary row transformation:
in the formula (14), the compound represented by the formula (I),B z indicating assembly error, Δ, of the measuring probea 6 Representing the twist error of the measurement point; removing redundant parameters to obtain an optimal surface parameter error formula as follows:
in equation (15), the matrix subscript r represents the minimized optimized rank; and (5) integrating the formulas (7) - (15), substituting the solution meeting the criterion as an initial value of the hybrid optimization shape surface measurement algorithm, and calculating to obtain an optimal solution.
As a further technical scheme of the invention, the turbine blade to be measured has the length c =150 mm and the maximum thickness u 0 =18 mm generator parts.
The invention has the beneficial and positive effects that:
different from the conventional technology, the method quickly and effectively solves the problems of poor shape precision and poor size consistency in the hybrid processing process, the Pro/ENGINEER software package is used for creating a 3D CAD model of the turbine blade, the profile parameters are used as input data of a computer system, the normal vector of a measuring point is generated by the computer system, the generated data is used for deriving a simulation graph from a display of the computer system in a DMIS format, and the simulation annealing algorithm and the least square method (SA-LM) hybrid optimization profile measuring algorithm are adopted to optimize the measured profile parameters, so that the precision of the shape and the size of the processed turbine blade is greatly improved.
Drawings
FIG. 1 is a flow chart of a method for measuring a profile of a turbine blade based on six-point positioning;
FIG. 2 is a schematic projection view of a CMOS camera;
FIG. 3 is a first schematic view of a six point positioning of a turbine blade;
FIG. 4 is a second schematic view of a six point positioning of a turbine blade;
FIG. 5 is a block diagram of a turbine blade measurement computer system;
the data points measured in the profile of fig. 6 are compared to the ideal profile.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, it being understood that the embodiments described herein are merely illustrative and explanatory of the invention, and are not restrictive thereof;
as shown in fig. 1, a method for measuring a profile of a turbine blade based on six-point positioning includes:
(S1) placing the turbine blade on a linear displacement table, and manually modulating a CMOS camera and a test facer to align the cross section and the surface of the turbine blade; CMOS cameras and test profilers use triangulation principles to project a structured line laser pattern onto one surface of the blade under test, the camera captures an image of the line and processes to interpret the distorted form of the projected line. By linear scanning of the instrument, the profile of another part of the blade can be measured. The results of comparison and evaluation of two symmetrical profiles of the NACA0012 series are given, one manufactured in a 3D printer and the other metallic profile AF104 of a subsonic wind tunnel. In addition, three sections of an FX 63-137 type blade of a 1.5 kW wind turbine were evaluated. Aerodynamic analysis shows that the lift coefficient and the aerodynamic profile efficiency are reduced, and the drag coefficient is increased. In addition, the sensitivity of the CMOS camera and the test profiler instrument in the Z axis was 0.1 mm.
(S2) projecting a structured line laser pattern onto one surface of the turbine blade to be tested, capturing an image of the contour line of the turbine blade by a CMOS camera and preprocessing the image, and measuring the contour line of the cross section of the other part of the turbine blade by testing the linear scanning of the faceting machine;
in a particular embodiment, laser Triangulation Techniques (LTT) are most commonly used for three-dimensional object reconstruction, as these techniques are based on triangulation between the object, the CCD and the structured light projection. The height variation in the profile is measured by the lateral displacement of a point in a ray (structured light) projected on the object to be measured. In addition, the LTT has the characteristics of simple structure, high measuring speed, flexibility and the like, and is widely applied to detection and quality control in the production process. However, the main drawback of LTT is the need for non-outdoor illumination sources and the color of the measured surface, thus requiring additional image processing methods to obtain a digital reconstruction of the wind turbine blade geometry. Among other work, the development of low cost scanner systems was introduced that reconstruct wind turbine blades using two projection and viewing systems to evaluate both sides (outer and inner) of the wind turbine blade. By using a dc motor with position and speed control feedback, the different profiles of the blade are reconstructed, causing it to be linearly displaced.
(S3) the Renishaw PH10T measuring probe picks up three points to form an X-Y plane, then two points are taken to define an X axis, and a rotating shaft of a turbine blade center hole is obtained to place a Z axis; the Renishaw PH10T measuring probe carries out six-point positioning on the turbine blade, and optimizes the parameters of the measured profile by mixing an optimized profile measuring algorithm;
in a particular embodiment, a british raney shao RENISHAW PH10T lateral head is used, the machine having three translational axes, an X-axis, a Y-axis and a Z-axis, and two rotational axes, an a-axis and a B-axis, which are capable of being rotated by an angular increment of 7.5 ° by 105 ° and 180 °, respectively. A total of 720 stylus orientations support measurement of complex surfaces. The control of the machine and its probe, as well as the input and retrieval of measurement data, is effected via the interface IEEE 488. When the rotation angle is normally used for detection, part of the angle can be rotated, but the angle which is rotated past cannot be locked, so that the measurement cannot be continued. The damage of the raney shaw side head is confirmed by the on-site detection of the PH10T side head, and needs to be maintained. Three-dimensional RenishawPH10T automatic seat fault detection: normal reset, angle rotation, etc. -cannot be used for normal measurement. And (4) maintaining a PH10T measuring head, an MH20 measuring head and a 3D image measuring instrument measuring head. Similar to pH 10M; except that the PH10T replaces the auto-adsorption adapter with an M8 screw probe base. All M8 threaded probes (e.g., TP20 and TP 200) and extension bars can be mounted directly on the base. PH10T is fully compatible with all stylus and module switching systems in renisha. With respect to developing a computer system to implement the above method to calculate probe orientation, ACIS developed by SpatialTechnology, inc. was used as the geometry kernel and VisualC was used as the programming language.
(S4) creating a 3D CAD model of the turbine blade using the Pro/ENGINEER software package, with the shape parameters as input data to the computer system, with the normal vectors of the measurement points being generated by the computer system, and with the generated data being derived from the display of the computer system in DMIS format.
In a particular embodiment, as shown in FIGS. 2-4, the six point locations are the leading edge point, trailing edge point, pressure side point, suction side point, large twist point and large camber point of the turbine blade,
in a particular embodiment, the CMOS camera is based on the projection of a laser line on a reference plane, the height variation in the profile of the turbine blade is measured by the lateral displacement of a point in the light projected on the object to be measured, the turbine blade is placed on a linear displacement table perpendicular to the Z-axis, the minimum displacement measurable by the CMOS camera is of the order of 1 pixel, assuming the coordinates of each point (X, Y, Z) of the projected laser line, the measurement sensitivity Δ of the CMOS camera is of the order of 1 pixelzObtained from equation (1):
in the formula (1), the reaction mixture is,a、band
respectively representing the focal length of the lens, the distance of the pinhole reference plane and the observation angle, deltaxRepresenting the amount of lateral displacement of the reference ray produced by the height variation over the selected contour along the projection line.
In one embodiment, the turbine blade surface requires constant rotation, is driven by an Applied Motion Products stepper motor, and is controlled by an Arduino Mega 2560 micro-control card.
In a specific embodiment, the contour lines of the cross-sections are fitted by using the leading edge points of each section curve, and the trailing edge curves are fitted by using the trailing edge points of the respective section curves; the section curve of the blade is represented by non-uniform rational B splines and a node sequenceU={uOn (c) }kRational B-spline curve of orderCHaving a parametric representation:
in the formula (2), the reaction mixture is,d i it is shown that the control point is,ithe sequence number is shown to indicate that,w i the weight is represented by a weight that is,Nrepresenting a B spline basis function on the node sequence U; leading edgeFitting curves by using a leading edge point of each section curve, fitting a trailing edge curve by using a trailing edge point of each section curve, sampling the leading edge curve and the trailing edge curve, setting L and T as sampling point sets of the leading edge curve and the trailing edge curve, respectively, and projecting L 'and T' on a blade stacking axis, wherein L 'is a projection point set corresponding to L and T' is a projection point set corresponding to T; for thePEach point of (1) throughD=||p 1 -p 2 I calculate the distance if D<2R, where R is the probe radius, thenP＝{p' i Is the final sampling point set, the section curve height can be from p' i Is expressed in terms of z-axis values.
In a specific embodiment, a turbine blade plane to be measured in the turbine blade, which is arranged at a blade shroud, is one of the serrated surfaces, and after a blank of the turbine blade is ground, the precision of the serrated surface is measured to determine that the turbine blade plane has been subjected to a pretreatment process. The deburring and cleaning work adopt a deburring magnetic polishing machine, the deburring magnetic polishing machine utilizes super-strong electromagnetic force to conduct a fine grinding stainless steel needle, high-speed flowing, turning and other actions are generated, and in a workpiece inner hole, surface friction is achieved, and precision grinding effects such as polishing, cleaning and burr removing are achieved. The deburring magnetic polishing machine is characterized by comprising precision part finished products of light iron metal, nonferrous metal, hard plastic and the like, and finishing precision grinding work such as deburring, chamfering, polishing, cleaning and the like at one time; irregular parts, holes, tubes, dead corners, cracks, etc. can be ground; the processing speed is high, the operation is simple and safe, and the cost is low; the finished product is not deformed after being processed, and the precision is not influenced; the machine type is complete, and a special machine type can be designed. The actual shape of the pre-process of the pre-treatment of the deburring and cleaning of the turbine blades is not known and may differ from each other even in the same batch. However, the actual shape of the pre-treatment pre-process of deburring and cleaning is the only guide to adapt to the nominal final shape and should be checked accurately. On-board measurement is an in-process measurement method in which a touch probe or measurement camera is mounted on the machine tool spindle to check the shape of the turbine blade.
In particular embodiments, the CAD model of the turbine blade is typically represented as a non-uniform rational spline surface. The CAD model is cut into a plurality of cross sections in the spanwise direction according to the design rules of the turbine blade shape, and cross section lines are generated. Since the contact probe cannot check the shape on line, the section lines should be dispersed into dots. There are several desperate approaches such as equidistant based, curvature based, equal volume based, etc. The present invention employs a six-point positioning measurement point based algorithm that reduces measurement time while maintaining a cross-sectional shape with a minimum of points. After the measurement points are generated, the next step is to plan the measurement path of the probe.
In a particular embodiment, the angle parameter between the measurement probe and the turbine blade is calculated assumingdIs the angle between two adjacent blades and is,
from the X-axis to a point P (P) passing through the measurement x ，P y ，P z ) Is rotated about an axis of the shaft,βis the angle at which the current measurement point rotates around the Z axis until the next blade is contacted, the three angles can be formulated as:
in the formula (3), the reaction mixture is,nis the total number of blades, angle of rotation
The expression is as follows:
in the formula (4), the reaction mixture is,uis a pointPSince the turbine blade is composed of a pressure surface and a suction surface, as shown in fig. 1, in calculating the rotation angle δ to avoid collision between the probe and the turbine blade, it is necessary to consider the surface on which the measurement point is located, and the angle of the measurement point on the pressure surface satisfies formula (5):
the angle satisfies formula (6) for a measurement point located on the suction surface:
in equations (5) and (6), the stylus rotation angle δ is such that the stylus is in the middle of the safety boundary, i.e. the angle between the stylus and either of the two safety boundaries is y/2, and the stylus must be rotated for each point to be measured whether a collision occurs or not.
In the specific embodiment, when the measuring probe measures the same point of the turbine blade, the coordinate values of the measuring probe are kept unchanged at different postures according to the theoretical model, but the shape parameters and the theoretical parameters have errors due to various factors, and in addition, the measurement errors are also related to the spatial positions, so that the measuring probe is required to measure multiple postures at different positions during calibration, and the error magnitude and the fluctuation range of the coordinate values are reflected by the precision of the measuring machine. Therefore, the method combines SA and LM as objective functions, and adopts a designed SA-LM hybrid optimization shape surface measurement algorithm to obtain the actual value of the shape surface parameter of the turbine blade. Measuring the turbine blade in different postures, and recording the obtained angle data to obtain coordinate values of a measuring point (x, y, z) The actual value of the measurement point is the average value of the multiple measurement data (x 0 , y 0 , z 0 ) Then the average value of the errors at the measurement points is:
in the formula (7), the reaction mixture is,ethe average value of the errors of the measurement points is represented,e i an error of the measuring point is indicated,ithe sequence number is shown to indicate that,nindicating the number of measurement points, in this embodimentn=6; the standard deviation of the measurement points was calculated as:
in the formula (8), the reaction mixture is,
the standard deviation of the measuring point is shown, and the overall measuring precision of the measuring probe is passedeAnd
expressed in combination, the objective function is:
in the formula (9), OA represents a measurement objective function, and whether the turbine blade profile parameter calculated by the measuring probe is close to a true value is judged according to the value of the objective function; the calculation by using a least square method can obtain:
in the formula (10), ΔSWhich represents a vector of error parameters that is,Jrepresenting the Jacobian matrix, ΔMRepresenting a measured coordinate error model; after calculating delta S according to the formula (10), correcting the measurement parameters, calculating a new round of theoretical coordinate values and an error matrix through the corrected parameters, judging that the error of the corrected parameters is smaller than a set threshold epsilon, and continuing iteration if the condition is not met; if the conditions are met, the operation is finished, and final parameters are output; when the Jacobian matrix J in the formula (10) is a singular matrix, if part of parameters in the matrix are in a linear relation, interference is caused to the solution of parameter errors; the transformation analysis is therefore performed to the left of the equation for the error model Δ S:
let K = (J) in formula (11) T ×J) -1 And carrying out singular value decomposition to obtain:
in the formula (12), the reaction mixture is,PandQfor orthogonal matrices, the matrix K is substituted back to equation (12) to obtain:
according to the matrix analysis in the formula (13), the profile parameters are known to have 6-rThe parameters have linear relation, and r is the rank of the matrix; since K is a symmetric matrix in the formula (12), there is a corresponding relationQ T ＝P -1 Therefore, the Q matrix belongs to a rotation matrix, and the error delta S model of the formula (13) is subjected to rotation transformation to place all the linearly related surface parameters on the same zero plane. Then will beQ T Middle and later 6-rThe initial row transformation is carried out on the row part so as to extract error parameters with linear relation in the matrix, and the final result is as follows:
in the formula (14), the reaction mixture is,B z indicating assembly error, Δ, of the measuring probea 6 Representing the twist error of the measurement point; deltaa 6 The matrix which is used as the redundant parameter and removes the corresponding parameter in the Jacobian matrix and the parameter error matrix Delta S can obtain a new profile parameter error formula, wherein the matrix Delta S isrRow 1 column, matrix J3 n rowsrColumns, the matrix Δ S being 3n rows and 1 column, i.e.
In equation (15), the matrix subscript r represents the minimized optimized rank; and (5) integrating the formulas (7) - (15), substituting the solution meeting the criterion as an initial value of the LM algorithm, and calculating to obtain an optimal solution.
In a specific embodiment, the turbine blade under test has a length c =150 mm and a maximum thickness u 0 Generator parts of =18 mm. The turbine blade measurement procedure involves adjusting the computer system to the field of view of the CMOS camera so that the displacement is measured through the larger side of the CMOS camera for optimal resolution, taking an image and rotating 180 ° to complete the profile of the part. Finally, the invention uses an image processing method which allows to obtain discrete data describing the measured section. The experimentally obtained profile is then compared with the theoretical profile of the NACA0012 series. The calibration process in this proposal is performed using linear displacement along the Z-axis, so that we can measure the lateral displacement of a point on the image plane to obtain a calibration curve with a sensitivity of 0.1 mm, while taking into account that the minimum displacement measurable on the image plane is about one pixel. For the reconstruction of each test profile, measurements are taken along 4 profiles, in particular only one of them, in order to compare the theoretical profile of equation (2) with the test profile (actual profile). The results of the comparison of the measured profiles (AF 104 and PLA) with the theoretical profile (NACA 0012). As shown in FIG. 6, a set of points for section AF104 more closely approximates the curve of section NACA0012, with an absolute deviation (RMS) of 0.07321 mm for the PLA section and 0.0373 mm for the AF104 section.
Although specific embodiments of the present invention have been described above, it will be understood by those skilled in the art that these specific embodiments are merely illustrative and that various omissions, substitutions and changes in the form and details of the methods and systems described above may be made by those skilled in the art without departing from the spirit and scope of the invention; for example, it is within the scope of the present invention to combine the steps of the above-described methods to perform substantially the same function in substantially the same way to achieve substantially the same result; accordingly, the scope of the invention is to be limited only by the following claims.
Claims (9)
1. A six-point positioning-based profile measuring method for a turbine blade is characterized by comprising the following steps of: the method comprises the following steps:
(S1) placing the turbine blade on a linear displacement table, and manually modulating a CMOS camera and a test facer to align the cross section and the surface of the turbine blade;
(S2) projecting a structured line laser pattern onto one surface of the turbine blade to be tested, capturing an image of the contour line of the turbine blade by a CMOS camera, preprocessing the image, and measuring the contour line of the other part of the cross section of the turbine blade by linear scanning of a test facer;
(S3) picking three points by a Renishaw PH10T measuring probe to form an X-Y plane, then taking two points to define an X axis, and obtaining a rotating shaft of a central hole of the turbine blade to place a Z axis; the Renishaw PH10T measuring probe carries out six-point positioning on the turbine blade, and optimizes the measured profile parameters by adopting an SA-LM hybrid optimization profile measuring algorithm;
(S4) creating a 3D CAD model of the turbine blade using the Pro/ENGINEER software package, the shape parameters as input data to the computer system, the normal vectors of the measurement points being generated by the computer system, the generated data being used to derive a simulation map in DMIS format by a display of the computer system.
2. The method of claim 1, wherein the method comprises the following steps: the six point locations are the leading edge point, trailing edge point, pressure side point, suction side point, large twist point, and large bend point of the turbine blade.
3. The method of claim 1, wherein the method comprises: the working method for capturing the image of the contour line of the turbine blade by the CMOS camera comprises the following steps:
the height variation in the profile of the turbine blade is measured by the transverse displacement of a point in a light projected on the object to be measured, based on the projection of the laser line on a reference plane, the turbine blade being placed on a linear displacement table perpendicular to the Z axis, the CMOS camera measuring the minimum displacement, assuming the coordinates of each point (X, Y, Z) of the projected laser lineIn the order of 1 pixel, the measurement sensitivity Delta of a CMOS camerazObtained from equation (1):
in the formula (1), the acid-base catalyst,a、band
respectively representing the focal length of the lens, the distance of the pinhole reference plane and the observation angle, deltaxRepresenting the amount of lateral displacement of the reference ray produced by the height variation over the selected contour along the projection line.
4. The method of claim 1, wherein the method comprises: the surface of the turbine blade is driven by a stepping motor and is controlled by a micro control card, so that continuous rotation is realized.
5. The method of claim 1, wherein the method comprises: the contour line of the cross section is fitted by using the leading edge point of each section curve, and the trailing edge curve is fitted by using the trailing edge point of each section curve; the section curve of the blade is represented by non-uniform rational B splines and a node sequenceU={uOn (c) }kOrder rational B-spline curveCWith the parameter representation:
in the formula (2), the reaction mixture is,d i it is shown that the control point is,ithe sequence number is shown to indicate that,w i the weight is represented by a weight that is,Nrepresenting a B spline basis function on the node sequence U; fitting the leading edge curves by using the leading edge points of each section curve, fitting the trailing edge curves by using the trailing edge points of the respective section curves, samplingSetting L and T as sampling point sets of the front edge curve and the rear edge curve respectively, and projecting L 'and T' on a blade stacking axis, wherein L 'is a projection point set corresponding to L, and T' is a projection point set corresponding to T; for thePEach point of (1) throughD=||p 1 -p 2 I calculate the distance if D<2R, wherein R is the probe radius, thenP＝{p' i Is the set final sampling point, the section curve height is p' i Is expressed in terms of z-axis values.
6. The method of claim 1, wherein the method comprises: the turbine blade to be measured is arranged at the blade crown in the turbine blade, the plane of the turbine blade to be measured is one of the sawtooth surfaces, and after the blank of the turbine blade is polished, the precision of the sawtooth surface is measured to determine that the pretreatment process is carried out on the plane of the turbine blade.
7. The method of claim 1, wherein the method comprises: calculation of the angular parameters between the measuring probe and the turbine blade, assumingdIs the angle between two adjacent blades and is,
from the X axis to a passing measurement point P (P) x ，P y ，P z ) Is rotated about an axis of the shaft,
is the angle at which the current measurement point rotates around the Z-axis until it contacts the next blade, the three angles can be formulated as:
in the formula (3), the reaction mixture is,nis the total number of blades, angle of rotation
The expression is as follows:
in the formula (4), the reaction mixture is,uis a pointPAt the thickness of the cross section, the rotation angle δ is calculated to avoid collision between the probe and the turbine blade, the angle satisfying formula (5) for the measurement point on the pressure surface:
the angle satisfies formula (6) for a measurement point located on the suction surface:
in equations (5) and (6), the stylus is rotated by an angle δ such that the stylus is in the middle of the safety boundary, i.e. the angle between the stylus and either of the two safety boundaries is y/2.
8. The method of claim 1, wherein the method comprises: the hybrid optimization shape surface measurement algorithm process comprises the following steps:
the measuring probe measures the turbine blade in different postures, and the actual value of the measuring point is the average value of multiple measuring data (x 0 , y 0 , z 0 ) Then the average value of the errors at the measurement points is:
in the formula (7), the reaction mixture is,ethe average value of the errors of the measurement points is represented,e i an error of the measuring point is indicated,ithe sequence number is shown to indicate that,nrepresents the number of measurement points; the standard deviation of the measurement points was calculated as:
in the formula (8), the reaction mixture is,
and (3) representing the standard deviation of the measuring points, wherein the overall measuring precision objective function of the measuring probe is as follows:
in the formula (9), OA represents a measurement objective function, and whether the turbine blade profile parameter calculated by the measuring probe is close to a true value is judged according to the value of the objective function; the calculation by using a least square method can obtain:
in the formula (10), ΔSWhich represents a vector of error parameters that is,Jrepresenting the Jacobian matrix, ΔMRepresenting a measured coordinate error model; transformation analysis was performed on the left side of the equation for the error model Δ S:
let K = (J) in formula (11) T ×J) -1 And carrying out singular value decomposition to obtain:
in the formula (12), the reaction mixture is,PandQfor orthogonal matrix, the matrix K is replaced by a loop (12)The following can be obtained:
according to the matrix analysis in the formula (13), the profile parameters are known to have 6-rThe parameters have linear relation, r is the rank of the matrix, willQ T Middle and later 6-rThe row part is subjected to primary row transformation:
in the formula (14), the compound represented by the formula (I),B z indicating assembly error, Δ, of the measuring probea 6 Representing the twist error of the measuring point; removing redundant parameters to obtain an optimal surface parameter error formula as follows:
in equation (15), the matrix subscript r represents the minimized optimized rank; and (5) integrating the formulas (7) - (15), substituting the solution meeting the criterion as an initial value of the hybrid optimization shape surface measurement algorithm, and calculating to obtain an optimal solution.
9. The method of claim 1, wherein the method comprises: the turbine blade to be measured has a length c =150 mm and a maximum thickness u 0 Generator parts of =18 mm.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115791887A (en) * | 2023-02-08 | 2023-03-14 | 北京汉飞航空科技有限公司 | Self-adaptive measurement algorithm of turbine blade based on six-point measuring tool |
| CN115890537A (en) * | 2023-03-07 | 2023-04-04 | 北京汉飞航空科技有限公司 | Posture adjusting method for turbine blade based on six-point positioning |
| CN117709007A (en) * | 2023-11-22 | 2024-03-15 | 九州云箭(北京)空间科技有限公司 | Turbine nozzle blade design method and system and turbine nozzle blade |
| CN117968570A (en) * | 2024-04-02 | 2024-05-03 | 成都和鸿科技股份有限公司 | Tenon tooth profile detection method and detection clamp |
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2023
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115791887A (en) * | 2023-02-08 | 2023-03-14 | 北京汉飞航空科技有限公司 | Self-adaptive measurement algorithm of turbine blade based on six-point measuring tool |
| CN115890537A (en) * | 2023-03-07 | 2023-04-04 | 北京汉飞航空科技有限公司 | Posture adjusting method for turbine blade based on six-point positioning |
| CN117709007A (en) * | 2023-11-22 | 2024-03-15 | 九州云箭(北京)空间科技有限公司 | Turbine nozzle blade design method and system and turbine nozzle blade |
| CN117968570A (en) * | 2024-04-02 | 2024-05-03 | 成都和鸿科技股份有限公司 | Tenon tooth profile detection method and detection clamp |
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