A robot-assisted positioning system and method for polishing aero-engine blades

Abstract

In the disclosed embodiment, a position alignment system and method for robot polishing of aero-engine blades are provided. The position alignment system for aero-engine blades collects blade profile data through a laser scanner, uses a registration and alignment algorithm to perform calculations, obtains a blade posture adjustment matrix, and a data transmission module transmits the transformation matrix to a processor to complete adaptive adjustment of the processing program and the robot motion path, thereby achieving precise polishing of the blades. Through the technical solution disclosed in the present application, the registration and alignment of the designated blade polishing processing positioning can be accurately completed, the position error can be reduced, and the contour accuracy of the blade after polishing can be ensured.

Description

Technical Field

[0001] The invention relates to the field of machining and positioning of aircraft engine blades, and in particular to a position alignment system and method for robot polishing of aircraft engine blades. Background Art

[0002] As the jewel in the crown of industry, aircraft engine blades are typical high-precision free-form surface parts that need to withstand extremely harsh working environments such as high temperature and high pressure. The accuracy of their surface contours directly affects the performance of the engine. Therefore, after CNC machining, the blades need to be ground and polished to form high-quality surfaces, which puts strict requirements on the accuracy of blade machining. Blades have a variety of complex curved surfaces, which are difficult to process and require high precision. One of the most prominent problems in the precision grinding and polishing process is that the positioning error caused by clamping and positioning affects the contour accuracy of the blades. Before precision grinding and polishing, position alignment of the blades can effectively reduce the position error, thereby ensuring contour accuracy.

[0003] As a part with multiple complex curved surfaces, it is impossible to ensure that the contour of each blade remains consistent. Therefore, the shape error between a single blade theoretical model and the actual object also affects the processing accuracy of the blade. The prior art does not have a mature position alignment adjustment method. In view of the above technical defects, the present application proposes an aircraft engine blade position alignment system and method. Summary of the invention

[0004] The alignment method provided by the present invention realizes the corresponding alignment function based on the aero-engine blade alignment system.

[0005] The aero-engine blade alignment system is composed of a laser scanner, a registration system, a processor and a clamping tool.

[0006] The laser scanner is responsible for data collection for the blade position alignment method. The scanner can switch between three modes: surface laser scanning, point laser scanning and line laser scanning. The surface laser scanning mode is used to identify the overall contour and surface features of the blade and to build an accurate theoretical model of a single blade. The point laser scanning mode is used for the initial alignment module of the blade. The point coordinates are collected in the four corner areas of the front and back sides of the blade and combined with the theoretical point coordinates to complete the initial alignment of the blade position. The line laser scanning mode is used to collect the coordinate point sets of multiple blade cross-section contour lines, and combine with the theoretical coordinate point sets to achieve precise alignment to determine the blade position.

[0007] The registration system collects data based on the laser scanner and calculates the blade posture adjustment matrix. The registration system is divided into three modules: model building, initial registration and fine registration.

[0008] Specifically, the model building module mainly constructs the theoretical model of the blade to be processed. Based on the blade contour data obtained by surface laser scanning, the precise theoretical model of the blade to be processed is constructed by CAD technology.

[0009] Specifically, the initial registration module is based on the Rodrigues matrix operation and is responsible for the initial registration of the blade. The laser scanner transmits the coordinates of the 8 sets of points on the front and back surfaces of the blade measured by the point laser to the processor. In the robot coordinate system, the standard deviation of the distance between the two point sets of the measurement point (p) and the theoretical point (q) collected by the point laser is calculated using the following formula as the standard error for evaluating the point set registration effect. If the error is too large, the registration is exited and the robot is commanded to re-grip the blade; if the error is within the allowable range, the Rodrigues matrix is ​​used to calculate the pose transformation matrix from the theoretical point (q) to the measurement point (p), which is used as the initial value for the subsequent precise registration, including the rotation matrix R and the translation matrix T, to complete the initial registration.

[0010]

[0011] Specifically, the precise registration module adds the least square method based on the Rodriguez matrix, obtains the accurate blade posture transformation matrix through several iterative calculations, and assumes the precise registration function of the blade. Specifically, the precise registration process is:

[0012] (1) In the robot coordinate system, the pose transformation matrices R and T obtained by rough registration are used to transform the coordinate point set of multiple blade contours collected by line laser to obtain new measurement points. The coordinate point set corresponding to the blade theoretical model is the theoretical point (q i ).

[0013] (2) Design an iterative procedure, with the input being the new measurement points (p) obtained by rough registration 1 ), theoretical points (q) and the number of contour lines (NL) of the line laser scanning blade.

[0014] (3) First, calculate the measurement points To all theoretical points (q 1 ~q n ) to find the minimum distance value and the corresponding theoretical point (q i ). i As the center, three points on each side are used as control points (q i-3 ,q i-2 ,q i-1 ,q i ,q i+1 ,q i+2 ,q i+3 ) According to the following formula, a spline curve is fitted to represent the contour line of this section of the blade. The number of contour lines (NL) can be used to group the coordinate point sets and perform calculations on each line as a whole.

[0015]

[0016] Among them, t and t 1 is a constant between 0 and 1.

[0017] (4) Calculate the measurement points The distance to the fitted cubic spline curve is used as the measurement point (p i ) to the theoretical point (q i ), and the point on the cubic spline curve with the smallest distance is taken as the new theoretical point corresponding to the measured point.

[0018] (5) Then, based on the new theoretical point With measuring point Subtract the centroid coordinates of each point set from the other:

[0019]

[0020] Calculate the two point sets at this time The rotation matrix H between them is decomposed by its singular value, and finally the posture transformation matrix R is obtained 1 , T 1 Starting from the second time, at each iteration, the pose transformation matrix needs to be updated, inheriting the previously calculated result:

[0021]

[0022] Use the pose transformation matrix to measure the points Transform and find new theoretical points The measurement point at this time The standard deviation (er 1 ) to make a judgment.

[0023]

[0024] (6) If the standard deviation is less than the set value, the final pose alignment matrix R is output F (R F =R 1 R), and T F (T F =R 1 ·T+T 1 ).

[0025] (7) If the standard deviation is greater than the set value, return to step (3) and update the measurement point to (p i i ), re-execute steps (2-5) to calculate the new pose transformation matrix R i , Ti and standard deviation (er i ), judge again until the standard deviation (er n ) is less than the set value, output the final pose alignment matrix R F (R F =R n R), and T F (T F =R n ·T+T n ), complete the precise alignment.

[0026] The blade tooling described is a simple tooling. The use of the blade alignment method provided by the present invention does not require the positioning ability of the tooling itself. Therefore, the end of the grinding and polishing robot using the method provided by the present invention can be equipped with a simple tooling, which only has a clamping function and does not need to carry a positioning sensor, thereby reducing the weight of the tooling and reducing costs. Furthermore, flexible materials are used in the clamping parts of the tooling. The use of flexible materials can reduce the damage to the tail of the blade when the tooling clamps the blade, improve the overall integrity of the blade, and under the premise of increasing the clamping force, the rigidity of the workpiece relative to the robot is slightly different from that of the rigid material fixture, which will not have a significant impact on the blade grinding and polishing process.

[0027] In addition, the present application also provides a computing device and a computer-readable storage medium for a robot position alignment system and method for polishing aircraft engine blades, characterized in that it includes a processor and a memory, and the memory stores a program that can be executed by the processor to implement the position alignment function of the robot polishing aircraft engine blades. When the computer executable instructions are called and executed by the processor, the computer executable instructions prompt the processor to implement the position alignment method of the robot polishing aircraft engine blades.

[0028] The beneficial effects of the present invention are: providing a robot polishing position alignment system and method for aircraft engine blades, forming a position alignment system through point, line and surface laser scanning combined with a simple tooling and registration system, and providing a complete alignment method, which can accurately complete the registration and alignment of the designated blade polishing positioning, reduce position errors, and ensure the contour accuracy of the blade after polishing. The end clamping tooling design adopted by the present invention uses flexible materials to reduce damage to the tail of the blade when the tooling clamps the blade, and improve the overall integrity of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 The present invention is a schematic diagram of the alignment calculation iterative process of a position alignment system and method for robot polishing of aero-engine blades;

[0031] Figure 2 A position alignment system and method for robot polishing of aero-engine blades is provided, and a schematic diagram of a tooling structure for clamping blades is provided;

[0032] Figure 3 A schematic diagram of a position alignment system and method for robot polishing of aircraft engine blades with a surface laser scanning mode;

[0033] Figure 4 A schematic diagram of a position alignment system and method for robot polishing of aero-engine blades with a point laser scanning mode;

[0034] Figure 5 The invention discloses a position alignment system and method for robot polishing of aero-engine blades, and a schematic diagram of a line laser scanning mode. DETAILED DESCRIPTION

[0035] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0036] The alignment method provided by the present invention realizes the alignment function of an aero-engine blade alignment system based on a registration alignment algorithm.

[0037] In this example, the industrial robot first follows the pre-set control program as shown in the attached Figure 2 The simple tool shown clamps the blade and takes the part out of the mounting rack, waiting for grinding and polishing. Specifically, the clamping part of the tool uses flexible material to reduce damage to the tail of the blade when the tool clamps the blade, so a larger clamping force can be safely set to ensure that the robot clamps the blade and moves stably to complete the processing.

[0038] The robot then holds the blade and enters the laser scanner working area, using the Figure 3The laser scanning mode shown in the figure is used to perform laser scanning on the front and back surfaces of the blade to collect sufficient point data for the subsequent establishment of an accurate theoretical model of a single blade. Figure 4 The point laser scanning mode shown in the figure collects 8 point coordinates in the four corners of the front and back surfaces of the blade for subsequent rough registration operations. Figure 5 The line laser scanning mode shown collects coordinate point sets of multiple blade cross-section contour lines for subsequent precise registration operations. All data collected by the above laser scanners are transmitted to the processor, where the establishment and registration calculation process of the corresponding theoretical model is completed. It should be emphasized that the blade position alignment method proposed in the present invention does not require the use of complex blade tooling. The tooling only needs to complete the clamping function and does not require a positioning sensor. This simplifies the tooling, reduces costs, and avoids the cumulative positioning errors caused by multiple measurements.

[0039] Then, in the processor, the profile point data obtained by the surface laser scanning is adjusted based on the existing standard data model of the blade to establish an accurate theoretical model of a single blade; the eight positioning points collected by the point laser and the corresponding positioning points of the theoretical model are calculated based on the Rodrigues matrix to calculate the pose transformation matrix R and T, which are used as the initial values ​​of the registration calculation to complete the rough registration. The cross-sectional contour line point set scanned by the line laser, the point data of the corresponding theoretical model, and the initial pose transformation matrix R and T obtained by the rough registration are used as input quantities, and the following is used to calculate the pose transformation matrix R and T. Figure 5 The registration algorithm shown in the figure obtains the accurate blade posture alignment matrix and completes the precise registration.

[0040] Finally, the processor adaptively adjusts the processing program and robot motion parameters based on the precise blade posture alignment matrix obtained by the registration calculation, thereby changing the robot's terminal processing path. During the processing, the blade posture is adjusted to cooperate with the grinding wheel grinder to complete the precision grinding and polishing of the blade to be processed.

[0041] Improve the overall integrity of the blade. Under the premise of increasing the clamping force, the rigidity of the workpiece relative to the machine vision is slightly different from that of the rigid fixture, which will not affect the grinding and polishing of the blade.

[0042] The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for aligning the position of a robot polishing an aero-engine blade, characterized in that: The following steps are included: S1: The laser scanner performs surface laser scanning on the engine blade, collects blade profile data and transmits it to the processor; S2: Using the blade surface data obtained by surface laser scanning in the processor, a theoretical model of the blade to be processed is constructed; S3: The robot holds the blade, uses point laser and line laser to collect blade data, and completes the registration operation in combination with the theoretical model data to obtain the blade's position transformation matrix in the robot coordinate system; S4: The processor adaptively adjusts the machining program and the robot motion path according to the posture transformation matrix to achieve precise grinding and polishing of the blade; in The registration calculation process in step S3 is: (1) In the robot coordinate system, the standard deviation of the distance between the measured point p and the theoretical point q collected by the point laser is calculated as the standard error for evaluating the point set registration effect. If the error is too large, the registration is exited and the robot is instructed to re-grip the blade. If the error is within the allowable range, the Rodriguez matrix is ​​used to calculate the pose transformation matrix from the theoretical point q to the measured point p as the initial value for subsequent precise registration, including the rotation matrix R and the translation matrix T. (2) In the robot coordinate system, the pose transformation matrices R and T obtained in (1) are used to transform the coordinate point set of multiple blade contours collected by the line laser to obtain new measurement points , the coordinate point set corresponding to the blade theoretical model is the theoretical point q, and the measured point is calculated according to To all theoretical points The distance between them, find the minimum distance value and the corresponding theoretical point , from a theoretical point of view As the center, 3 points on each side as control points Fit the spline curve to represent the blade contour and calculate the measurement points The distance to the fitted cubic spline curve is used as the measurement point To the theoretical point The minimum distance, and the point on the spline curve corresponding to the small distance is used as the new theoretical point corresponding to the measured point ; (3) Based on the new theoretical point With measuring point , with the minimum standard deviation as the goal, the least squares method is used to calculate the pose transformation matrix , and then inherit the result of the last iteration , update the calculated pose transformation matrix ; (4) Calculation of new theoretical points With the transformed matrix New measuring point after alignment If the standard deviation does not meet the requirement, repeat steps (2) and (3) and change the measurement point to Continue the registration calculation and keep updating the transformation matrix ; When the standard deviation is less than the set value, the updated posture transformation matrix is ​​output ,and .

2. A method for aligning the position of a robot for polishing an aero-engine blade according to claim 1, characterized in that: In steps S1 and S3, in collecting three-dimensional laser data of points, lines and surfaces of the engine blades, the same laser scanner is used to switch the working mode.

3. The method for aligning the position of a robot for polishing an aero-engine blade according to claim 1, characterized in that: In step S2, based on the blade surface data obtained by surface laser scanning, a theoretical model of the blade to be processed is constructed in the processor using CAD technology.

4. The method for aligning the position of a robot for polishing an aero-engine blade according to claim 1, characterized in that: The registration calculation in step S3 is implemented based on the Rodriguez matrix and the least squares method.

5. A robot positioning system for polishing aircraft engine blades, characterized in that: The alignment system is composed of a laser scanner, a registration system, a processor, a robot and a clamping tool, and implements the alignment method as claimed in claim 1.

6. The position alignment system for robot polishing of aircraft engine blades according to claim 5, characterized in that: The clamping tool is made of flexible material at the position in contact with the blade.

7. A computer device, characterized in that: The method comprises a processor and a memory, wherein the memory stores computer executable instructions that can be executed by the processor, and the processor executes the computer executable instructions to implement the method according to any one of claims 1 to 4.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions. When the computer-executable instructions are called and executed by a processor, the computer-executable instructions prompt the processor to implement the method according to any one of claims 1 to 4.

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