Aero-engine composite blade clamping system and its lattice support force control method

Abstract

This invention discloses a clamping system for composite blades of aero-engines and its dot matrix support force control method. The clamping system includes a support module, a positioning module, and a clamping module. The positioning and clamping units adopt a dot matrix design. Combined with the support force control method designed for this system, the support force is coordinated and controlled. It can adaptively position and clamp aero-engine blades with different curvatures, and adaptively adjust the attitude of blades of the same type to adapt to existing CNC machining toolpaths. This avoids the complex operation of re-scanning, calculating, modeling, and planning CNC machining toolpaths due to attitude changes. At the same time, it can meet multiple processes in the manufacturing of aero-engine blades, such as blade edge and tenon root machining, simplifying the machining process of aero-engine blades and improving the machining efficiency and quality of blades.

Description

Technical Field

[0001] This invention relates to a composite blade clamping system for aero-engines and a method for controlling the lattice support force thereon, belonging to the field of aero-engine technology. Background Technology

[0002] As a representative of high-tech components, achieving high-precision adaptive clamping of composite material blades for aero-engines is an important research issue. For example... Figure 1 As shown, the structure of an aero-engine blade mainly consists of a complex free-form blade body and tenons for connecting the rotor disc. The twist angle and radius of curvature of the entire blade profile vary considerably. This profile is defined by multiple cross-sections formed by the smooth transition of the inlet leading edge, the exhaust trailing edge, and two spline curves. Therefore, aero-engine blades are typical complex curved thin-walled parts with excellent aerodynamic performance.

[0003] The processing quality of each part of the aero-engine blade is closely related to the working life of the aero-engine. The main structural functions are as follows: (1) Blade body: The blade body can be divided into blade basin and blade back according to the shape of the surface. The part that forms the "arched back" is called the blade back, which mainly bears pressure; the part that forms the "concave basin" is called the blade basin, which mainly bears suction. Usually, the blade body profile is obtained by connecting the designed point set or calculating the curve equation through aerodynamic parameter design. Then, the accumulated points on each section are connected by a smooth curve to generate the complex curved surface of the blade body. (2) Blade leading / trailing edge: The curved surface between the blade back and the blade basin is called the inlet leading edge and the exhaust trailing edge of the blade, respectively. In the working state, the edge where the airflow flows in is called the leading edge or inlet edge, and the edge where the airflow flows out is called the trailing edge or exhaust edge. The profile shape of the blade inlet and exhaust edges will directly affect the power performance of the engine. Its geometric profile has evolved from the early arc shape to the ellipse shape, as well as the more precise segmented spline curve design. To prevent the adhesive layer of the composite blade from delaminating during high-speed rotation and to improve the blade's impact resistance, a titanium alloy strip is used to wrap the leading edge of the blade. (3) Tenon: The tenon is the assembly part that connects the blade to the wheel. It bears a large amount of centrifugal force during operation and its main function is to ensure the stability of the blade during operation. The tenon requires very high assembly and machining accuracy.

[0004] The clamping of aero-engine blades involves two processes: positioning and clamping. Positioning is the process of ensuring the workpiece occupies the correct position on the machine tool or in the fixture, while clamping is the process of preventing the workpiece's positioning from being disrupted during machining. The clamping process is essentially the process of achieving mechanical equilibrium. The resultant force and resultant torque acting on the workpiece should be zero, also known as equilibrium constraint. Satisfying the equilibrium constraint means that the workpiece and the fixture system have reached a state of equilibrium at a certain point, but it does not guarantee that the workpiece's position is completely fixed. During clamping, it is necessary to ensure that the workpiece is in full contact with each positioning element without relative slippage, i.e., the supporting force of the positioning elements on the workpiece is greater than zero. This process is called stability constraint.

[0005] The geometric structure of composite material blades for aero-engines is analyzed. The clamping difficulties during tenon cutting include the following aspects: (1) Aero-engine blades are complex curved surface parts. The profile shape of each section of the blade body is different. The existing clamping system is difficult to generate positioning and clamping units that match the blade surface, resulting in inaccurate positioning and unstable clamping. (2) Since aero-engine blades are typical thin-walled parts with low stiffness, the existing clamping system is prone to uneven stress distribution, which can easily cause corresponding clamping deformation. This leads to differences between the geometric parameters of the blade surface and the theoretical model, affecting the machining accuracy of the blade tenon. (3) Blades are mass-produced parts, but each blade needs to be manufactured using a single-piece manufacturing process, resulting in a long production cycle and low efficiency. Therefore, adaptive attitude adjustment of the same type of aero-engine blades to match the existing CNC machining toolpaths avoids the repetitive operation of recalculating and planning CNC machining toolpaths due to attitude changes. At the same time, it can meet the needs of multiple processes in the manufacturing of aero-engine blades, such as blade edge and tenon root machining. Simplifying the machining process of aero-engine blades and improving the machining efficiency and quality of aero-engine blades are issues that need to be considered in the current clamping system design. Summary of the Invention

[0006] The purpose of this invention is to provide a clamping system for composite blades of aero-engines and a method for controlling the lattice support force thereon, in order to solve the problems of inaccurate positioning, unstable clamping, easy clamping deformation, low processing efficiency and poor processing quality in the existing aero-engine blade clamping system.

[0007] The present invention adopts the following technical solution:

[0008] A composite blade clamping system for aero-engines includes a support module, a positioning module, and a clamping module. The support module includes a clamping system base and a fixing platform. The upper surface of the clamping system base is a mounting surface, and the fixing platform is fixedly mounted on the mounting surface. Positioning holes are formed on the upper surface of the fixing platform. The positioning module includes a flexible positioning dot matrix and flexible attitude adjustment push rods. The flexible positioning dot matrix includes positioning units installed in each positioning hole. Each positioning unit includes a vertically arranged ball joint push rod and a push rod drive mechanism for driving the ball joint push rod to move up and down. The upper end of the ball joint push rod has a... A spherical end rests on the aero-engine blade, extending from a positioning hole. The flexible attitude adjustment push rod includes a push rod body located circumferentially around the aero-engine blade and a push rod body drive component that moves the push rod body toward the aero-engine blade. A chuck is provided at the front end of the push rod body near the leading edge, trailing edge, and tip of the aero-engine blade, for clamping the edge of the aero-engine blade. A push head is provided near the tenon root of the aero-engine blade for pushing the tenon root. An attitude adjustment push rod support frame is fixed to the support module, and the push rod body drive component is fixed to the attitude adjustment... The clamping module includes a vacuum adsorption mechanism and an auxiliary clamp on the push rod support frame. The vacuum adsorption mechanism includes a vacuum suction cup and a fixing component. The fixing component is used to fix the vacuum suction cup to the fixed platform. An angle adjustment component for adjusting the vacuum suction cup is connected between the fixing component and the vacuum suction cup. The vacuum adsorption mechanism is located outside the positioning unit. There is at least one positioning unit on the outer periphery of each vacuum adsorption mechanism, and at least one positioning unit between two adjacent vacuum adsorption mechanisms. The auxiliary clamp includes a clamp base, a leaf back contouring component, and a leaf basin contouring component. The clamp base is fixed to the clamping system base. The blade back profile is attached to the fixture base at both ends. The two ends of the blade back profile are located on the outer sides of the leading and trailing edges of the aero-engine blade, respectively. The two ends of the blade back profile and the blade basin profile are connected together by detachable connectors. The blade back profile has a concave surface that matches the back of the aero-engine blade, and the blade basin profile has a convex surface that matches the front of the aero-engine blade. The convex surface of the blade back profile and the concave surface of the blade basin profile match the back and front of the aero-engine blade, respectively. The blade back profile and the blade basin profile are connected together to clamp and position the aero-engine blade.

[0009] Furthermore, the positioning unit is vertically installed in the positioning hole, and the positioning unit consists of the following components from top to bottom: ball head push rod, dust cover, force sensor, slide assembly, ball screw, screw nut, screw housing, worm gear reducer, servo motor, encoder, limit switch, etc. The movement of each flexible positioning unit can be controlled independently or in conjunction with other positioning units.

[0010] Furthermore, there are three fixing platforms, which are arranged sequentially from the tenon root of the aero-engine blade towards the blade tip as a first fixing platform, a second fixing platform, and a third fixing platform. The first fixing platform has a first platform plate, a second platform plate, and a third platform plate. The first platform plate is parallel to the horizontal plane and close to the leading edge of the blade. The second platform plate and the third platform plate are both inclined surfaces that slope downward from the trailing edge to the front edge of the blade, with the second platform plate being lower than the third platform plate. The second fixing platform has a fourth platform plate, a fifth platform plate, a sixth platform plate, and a seventh platform plate. The fourth platform plate and the fifth platform plate are both parallel to the horizontal plane and are close to the leading edge of the blade. The fifth platform plate is located in the middle and is higher than the fourth platform plate. The sixth platform plate and the seventh platform plate are both inclined surfaces that slope downward from the trailing edge to the front edge of the blade, with the seventh platform plate being lower than the sixth platform plate. The third fixing platform has an eighth platform plate and a ninth platform plate. The eighth platform plate and the ninth platform plate are both parallel to the horizontal plane, with the eighth platform plate being lower than the ninth platform plate. The ninth platform plate is close to the fifth platform plate and the seventh platform plate of the second fixing platform.

[0011] Furthermore, the first, second, and third platforms each have 6 positioning holes, the fourth platform has 12 positioning holes, the fifth platform has 8 positioning holes, the sixth and seventh platforms each have 2 positioning holes, the eighth platform has 20 positioning holes, and the ninth platform has 9 positioning holes; the first, second, and third platforms each have 6 vacuum adsorption mechanisms, the fourth platform has 12 vacuum adsorption mechanisms, the fifth platform has 8 vacuum adsorption mechanisms, the sixth and seventh platforms each have 2 vacuum adsorption mechanisms, and the third fixed platform has a total of 18 vacuum adsorption mechanisms.

[0012] Furthermore, the vacuum suction cup is an accordion-style vacuum suction cup; the vacuum suction cup is made of rubber.

[0013] Furthermore, there are two first fixing platforms, which are spaced apart along the direction from the tenon root to the blade tip; the second fixing platform and the third fixing platform are spaced apart; there are two sets of auxiliary clamps, which are used to clamp the positions of the aero-engine blades near the blade tip and the tenon root, respectively. The clamp base of the first set of auxiliary clamps is located between the two first fixing platforms, and the clamp base of the second set of auxiliary clamps is located between the second fixing platform and the third fixing platform.

[0014] Furthermore, the attitude adjustment push rod support frame is fixedly connected to the side of the fixed platform.

[0015] Furthermore, the two ends of the leaf back contouring component are respectively connected to the fixture base by a fixed pivot pin and a detachable pivot pin.

[0016] Furthermore, a flexible protective layer is provided on the convex surface of the leaf back profile and the concave surface of the leaf basin profile.

[0017] Furthermore, the mounting platform is provided with an origin coordinate hole and a grid-like scale line, and the side of the clamping system base is provided with a transfer insertion hole.

[0018] Furthermore, the adjustment components include a height adjustment component and an angle adjustment component.

[0019] A method for controlling the lattice support force of a composite blade clamping system for aero-engines, characterized in that the method includes the following steps:

[0020] S1: Acquisition of multi-point positioning motion data; First, control each positioning unit to perform axial fine-tuning in sequence, without disrupting the relative stability of the workpiece, while keeping other positioning units stationary during the fine-tuning process; Then, record the displacement of the positioning units, the supporting force, and the spatial motion of the workpiece's center of mass during the fine-tuning process;

[0021] S2: Motion data processing; Motion data processing includes the following steps: S201: Calculate the Spearman correlation coefficient between each positioning unit and other positioning units based on the support force data recorded in S1; S202:

[0022] Calculate the pose influence coefficient based on the workpiece's center of mass motion data; S203: Use the least squares method to establish a mathematical model of force coupling between the positioning unit's support force and the negatively correlated force-coupled axial displacement.

[0023] S3: Acquisition of current force information of positioning dot matrix; Obtain the force situation of each positioning unit in the current actual positioning process through force sensors, and determine the positioning units that need force compliance control and the positioning units that are close to the maximum force threshold.

[0024] S4: Support Force Coordination Control; Support Force Coordination Control includes the following steps: S401: Locate the overload warning axes in the coupled axis array and eliminate these units; S402: Locate the positioning units in the coupled axis array that have a positive correlation coefficient with the overload warning axes and eliminate these units to prevent the addition of new overload axes during the adjustment process; S403: Calculate the displacement required for the positioning units in the coupled axis array based on the force coupling mathematical model established in S2. In order to minimize the impact on the workpiece pose, select the positioning unit with the smallest product of displacement and pose influence coefficient as the optimal adjustment axis, and then control the optimal adjustment axis to move axially according to the displacement calculated by the mathematical model;

[0025] S5: Detect the overload axis of the positioning matrix and determine whether the overload axis has been cleared. If the overload axis has not been cleared, return to S3 according to the current force state of the positioning matrix. If the overload axis has been cleared, the matrix support force coordination control method has been completed.

[0026] Furthermore, S2 uses the Spearman correlation coefficient to calculate and evaluate the correlation of support forces between positioning units. For two adjacent flexible support units a and b, when a is controlled to extend axially a certain distance, the force dataset collected for a and b is X = {X1, X2, ..., X...} n} and Y = {Y1,Y2,...,Y} n Sort X and Y simultaneously in ascending or descending order to obtain two sorted sets of elements x = {x1, x2, ..., xy}. n} and y = {y1, y2, ..., y n}, for each element X in set X i Let the position of the element in set x be denoted as a. i To set each element Y in set Y i Let b be the position of the element in set y. i This yields the ranking sets a and b corresponding to X and Y. Subtracting each element in sets a and b yields the ranking difference set d, where d... i =a i -b i The Spearman correlation coefficient between X and Y can be obtained from d, calculated using the following formula:

[0027]

[0028] Where r s The value range of r is [-1, 1]. s The closer the absolute value of r is to 1, the closer the data sample sets X and Y are to being perfectly monotonically correlated. s When r < 0, it indicates that X and Y are negatively correlated; that is, when r < 0, it indicates that X and Y are negatively correlated. s When r > 0, it indicates that X and Y are positively correlated; when r s When the value is 0, it indicates that X and Y are completely uncorrelated. When the support force of a certain positioning unit is too large, a positioning unit that is negatively correlated with its force (i.e., the Spearman correlation coefficient is less than zero) is selected for adjustment to reduce the support force of that positioning unit.

[0029] Furthermore, the method for establishing the force coupling mathematical model between the positioning unit support force and the negatively correlated force coupled axial displacement using the least squares method described in step S203 is as follows: Assume there exists a sample dataset (x... i ,y i (i = 0, 1, ..., m), let its fitting function be the following:

[0030]

[0031] Where n is the maximum order of the fitted function; θ j(j=0,1,…,n) are the coefficients of the polynomial; then the sum of squared errors of the fitted function can be obtained as follows:

[0032]

[0033] Due to the coefficients θ j To minimize the sum of squared errors S, S modulo the coefficients θ of each polynomial. j The partial derivatives should satisfy the following two equations:

[0034]

[0035] From the above equation, the coefficients θ of the fitted function f can be obtained. j The fitting calculation is complete;

[0036] During the fine-tuning of the positioning matrix, there is a nonlinear relationship between the supporting force of a positioning unit and the displacement of its coupled positioning units, which can be expressed as follows:

[0037]

[0038] In the formula, F1 is the supporting force of the target positioning unit that needs to be adjusted; x0 is the displacement of the target positioning unit coupled with the positioning unit. Therefore, the input of the mathematical model of force coupling between the positioning unit supporting force and the negatively correlated force coupling axis displacement described in step S203 is the displacement of the positioning unit, and the output is the force on the target positioning unit.

[0039] Furthermore, the calculation method for the influence coefficient of the positioning unit on the workpiece pose is defined as follows:

[0040]

[0041] In the formula, Δx is the displacement of the workpiece on the x-axis (mm); Δy is the displacement of the workpiece on the y-axis (mm); Δz is the displacement of the workpiece on the z-axis (mm); and Δd represents the fine-tuning distance of the positioning unit (mm).

[0042] The beneficial effects of this invention are:

[0043] 1. The aero-engine composite blade clamping system and its dot matrix support force control method designed in this invention can adaptively adjust the blade's attitude to adapt to existing CNC toolpaths, so that blades of the same model can be accurately positioned on the clamping system. This allows for milling of the tenon root without changing the CNC code, saving the time required to modify the CNC code in the prior art, which is beneficial to improving the production efficiency of blades and reducing the cost of process document management.

[0044] 2. The aero-engine composite blade clamping system and its dot matrix support force control method designed in this invention feature a separation design for positioning and clamping. Real-time feedback from force sensors on the blade's force allows for smooth adjustment of the positioner's support force and the suction cup's clamping force, reducing blade clamping deformation. Simultaneously, this design facilitates small-range attitude adjustment of the blade using the attitude adjustment push rod, allowing the blade to move on the ball joint push rod and achieving rapid blade clamping.

[0045] 3. The aero-engine composite blade clamping system and its lattice support force control method designed in this invention ensure that the blade body and tenon remain open during the positioning and clamping process. The clamping system does not obstruct the measuring points on the blade, reducing interference between the measuring instrument and the clamp, and thus improving the accuracy and efficiency of measuring the complex curved surfaces of the blade body.

[0046] 4. The aero-engine composite blade clamping system and its lattice support force control method designed in this invention can meet the requirements of multiple processes in aero-engine blade manufacturing, such as blade edge and tenon machining. The auxiliary fixture can be easily installed or removed according to different processes using detachable pivot pins. Installing the auxiliary fixture during tenon machining further stabilizes the blade clamping; removing the auxiliary fixture during blade edge machining provides space for the cutting tool, improving machining efficiency and quality. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the structure of an aero-engine blade;

[0048] Figure 2 This is a schematic diagram of the overall system for clamping composite blades for aero-engines according to the present invention.

[0049] Figure 3 yes Figure 2 Schematic diagram of the distribution of flexible positioning points;

[0050] Figure 4 yes Figure 2 Schematic diagram of the distribution of the vacuum adsorption mechanism;

[0051] Figure 5 yes Figure 2 A schematic diagram of the component distribution inside the positioning unit;

[0052] Figure 6 yes Figure 2 Assembly diagram of components inside the positioning unit;

[0053] Figure 7 yes Figure 2 Schematic diagram of the platform position on the fixed platform;

[0054] Figure 8 yes Figure 2 Schematic diagram of the position distribution of the attitude adjustment push rod;

[0055] Figure 9 yes Figure 2 Schematic diagram of the medium vacuum adsorption mechanism;

[0056] Figure 10 yes Figure 2 Schematic diagram of the auxiliary fixture structure;

[0057] Figure 11 yes Figure 2 Schematic diagram of the base structure of the clamping system;

[0058] Figure 12 yes Figure 2 Schematic diagram of the distribution of the flexible positioning dot matrix and vacuum adsorption mechanism;

[0059] Figure 13 This is a flowchart of the lattice support force control method for the aero-engine composite blade clamping system of the present invention;

[0060] Figure 14 This is a schematic diagram of the coupling relationship of the support forces of two flexible support units, a and b.

[0061] Wherein: 1-Leading edge of blade; 2-Blade body; 3-Leading edge of blade; 4-Tongue root; 5-Ball head push rod; 6-Dust cover; 7-Force sensor; 8-Slide assembly; 9-Ball screw; 10-Screw nut; 11-Screw housing; 12-Motor; 13-Worm gear reducer; 14-Encoder; 15-First plate; 16-Second plate; 17-Third plate; 18-Fourth plate; 19-Fifth plate; 20-Sixth plate; 21-Seventh plate; 22- Eighth mounting plate; 23-Ninth mounting plate; 24-Tenon root adjustment push rod; 25-Blade trailing edge adjustment push rod; 26-Blade tip adjustment push rod; 27-Blade leading edge adjustment push rod; 28-Accordion-type vacuum suction cup; 29-Blade back contouring clamp; 30-Blade base contouring clamp; 31-Fixing pivot pin; 32-Clamp base; 33-Mounting platform; 34-Origin coordinate hole; 35-Transfer insertion hole; 36-Scale line; 37-Vacuum adsorption mechanism; 38-Flexible positioning dot matrix. Detailed Implementation

[0062] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The detailed descriptions provided below are for illustrative purposes only and are not intended to limit the scope of the invention.

[0063] An embodiment of the present invention provides a clamping system for composite blades in aero-engines, such as... Figures 2 to 12As shown, the aero-engine composite blade clamping system of this embodiment includes a support module, a positioning module, and a clamping module. The support module includes a clamping system base and a fixing table. The upper surface of the clamping system base is a mounting surface 33, on which scale lines and origin coordinate holes 34 are machined to facilitate blade calibration, scanning, and other operations. The transfer insertion hole 35 facilitates the transportation and handling of the clamping system. The fixed platform is fixedly installed on the mounting surface 33, and the upper surface of the fixed platform is provided with positioning holes. The positioning module includes a flexible positioning dot matrix 38 and a flexible attitude adjustment push rod. The flexible positioning dot matrix 38 includes positioning units installed in each positioning hole. Each positioning unit includes a vertically arranged ball-head push rod 5 and a push rod drive mechanism for driving the ball-head push rod to move up and down. The upper end of the ball-head push rod 5 rests on the aero-engine blade. When clamped, the ball-head push rod 5 contacts the curved surface of the composite blade, which plays a role in supporting the blade. The dust cover 6 can prevent the chips generated during the blade processing from entering the positioning unit and damaging the equipment. The force sensor 7 monitors the force of the current positioning point in real time and transmits the force. Force information is fed back to the industrial control computer. The main function of the slide assembly 8 is to guide the positioning unit to perform reciprocating linear motion along the z-axis, and at the same time fix the positioning unit to the box plate of the clamping system. The ball screw 9 is the transmission element of the positioning unit, which converts the rotational motion of the motor 12 into high-precision linear motion of the positioning unit along the z-axis. The worm gear reducer 13 is used to reduce the speed of the motor 12 and increase the output torque. The worm gear reducer 13 not only has reverse self-locking property, which is suitable for the positioning unit that plays a supporting role in the clamping process of composite blades, but also allows the input shaft and output shaft to be on different axes. In the clamping system, the overall height of the positioning unit can be reduced, making full use of the internal space of the clamping system.The ball-head push rod 5 extends from the positioning hole. The flexible attitude adjustment push rod includes a push rod body located circumferentially around the aero-engine blade and a push rod body drive component that drives the push rod body to move toward the aero-engine blade. A chuck is provided at the front end of the push rod body near the leading edge 1, trailing edge 3, and tip of the aero-engine blade. The chuck is used to clamp the edge of the aero-engine blade. A push head is provided near the tenon root 4 of the aero-engine blade for pushing the tenon root 4. An attitude adjustment push rod support frame is fixed on the support module, and the push rod body drive component is fixed on the attitude adjustment push rod support frame. The clamping module includes a vacuum adsorption mechanism and auxiliary clamps. The vacuum adsorption mechanism 37 includes an accordion-style vacuum suction cup 28 and a fixing component. The fixing component is used to fix the connection to the fixed platform. An adjustment component is connected between the fixing component and the accordion-style vacuum suction cup 28 for adjusting the angle and height of the accordion-style vacuum suction cup 28. The vacuum adsorption mechanism is located at the positioning... Outside the unit, there is at least one positioning unit on the periphery of each vacuum adsorption mechanism, and at least one positioning unit between two adjacent vacuum adsorption mechanisms; the auxiliary fixture includes a fixture base 32, a blade back contouring fixture 29, and a blade basin contouring fixture 30. The fixture base 32 is fixed on the clamping system base. The two ends of the blade back contouring fixture 29 are respectively connected to the fixture base 32. The two ends of the blade back contouring fixture 29 are located outside the leading edge 1 and trailing edge 3 of the aero-engine blade, respectively. The two ends of the blade back contouring fixture 29 and the blade basin contouring fixture 30 are respectively connected together by detachable connectors. The blade back contouring fixture 29 has a concave surface that matches the back of the aero-engine blade, and the blade basin contouring fixture 30 has a convex surface that matches the front of the aero-engine blade. The convex surface of the blade back contouring fixture 29 and the concave surface of the blade basin contouring fixture 30 match the back and front of the aero-engine blade, respectively. The blade back contouring fixture 29 and the blade basin contouring fixture 30 are connected together to clamp and position the aero-engine blade. When the blade is being tenoned, an auxiliary fixture is used to assist in clamping the blade and prevent chattering during processing, which could lead to product scrap. This auxiliary fixture can be removed during the machining of the leading and trailing edges of the blade to avoid interference with the machining tools. To protect the blade's surface from damage, a soft rubber protective layer is applied to the blade basin and blade back contouring fixtures.

[0064] The positioning unit is vertically installed in the positioning hole. The positioning unit consists of the following components from top to bottom: ball head push rod 5, dust cover 6, force sensor 7, slide assembly 8, ball screw 9, screw nut 10, screw box seat 11, worm gear reducer 13, motor 12, encoder 14, and limit switch, etc. The movement of each flexible positioning unit can be controlled independently or in conjunction with other positioning units.

[0065] The ball-end push rod contacts the curved surface of the composite blade during clamping, supporting the blade. A corrugated telescopic dust cover prevents chips generated during blade processing from entering the positioning unit and damaging the equipment. A force sensor monitors the force at the current positioning point in real time and feeds this information back to the industrial computer. The slide assembly guides the positioning unit's reciprocating linear motion along the z-axis while simultaneously securing it to the fixture box. The ball screw is the transmission element of the positioning unit, converting the motor's rotational motion into high-precision linear motion along the z-axis. A reducer lowers the motor's speed and increases output torque. The worm gear reducer not only has reverse self-locking properties, making it suitable for supporting the positioning unit during composite blade clamping, but also allows the input and output shafts to be on different axes. In adaptive clamping fixtures, this reduces the overall height of the positioning unit, fully utilizing the fixture's internal space. The movement of each flexible positioning unit can be controlled independently or in conjunction with other positioning units. Incremental encoders are used to provide feedback control for motor speed, and absolute encoders are used to provide feedback control for ball screw rotation angle, thereby improving the motion accuracy of the positioning unit.

[0066] Flexible attitude adjustment push rods are used to adjust the blade's posture. Their mechanical structure and control method are largely the same as the flexible positioning unit, the difference being that, except for the tenon root push rod, the top of the other attitude adjustment push rods is replaced by a clamping plate instead of a ball joint, facilitating blade posture adjustment. The tooling platform has a total of eight attitude adjustment push rods. By using the tenon root and blade tip attitude adjustment push rods in combination, the blade's posture can be adjusted along the x-axis; the blade leading edge attitude adjustment push rod can adjust the blade's posture along the y-axis; and by using the blade leading edge and trailing edge attitude adjustment push rods in combination, the blade's rotational posture can be adjusted along the z-axis. All attitude adjustment push rods return to their initial positions during tenon root machining and leading / leading edge machining of the blade, providing space for the tool to travel.

[0067] Furthermore, there are three fixing platforms, which are arranged sequentially from the tenon root 4 of the aero-engine blade towards the blade tip as a first fixing platform, a second fixing platform, and a third fixing platform. The first fixing platform has a first platform plate 15, a second platform plate 16, and a third platform plate 17. The first platform plate 15 is parallel to the horizontal plane and close to the leading edge 1 of the blade. The second platform plate 16 and the third platform plate 17 are both inclined surfaces that slope downward from the trailing edge 3 of the blade towards the leading edge 1 of the blade. The second platform plate 16 is lower than the third platform plate 17. The second fixing platform has a fourth platform plate 18, a fifth platform plate 19, a sixth platform plate 20, and a seventh platform plate 21. The fourth platform plate 18 and the fifth platform plate 19 are arranged in a certain order. All plates 19 are parallel to the horizontal plane. The fourth plate 18 is close to the leading edge of the blade. The fifth plate 19 is located in the middle and is higher than the fourth plate 18. The sixth plate 20 and the seventh plate 21 are both inclined surfaces close to the trailing edge 3 of the blade. The sixth plate 20 and the seventh plate 21 are both inclined downward from the trailing edge 3 of the blade to the leading edge 1 of the blade. The seventh plate 21 is lower than the sixth plate 20. The third fixed platform has an eighth plate 22 and a ninth plate 23. The eighth plate 22 and the ninth plate 23 are both parallel to the horizontal plane. The eighth plate 22 is lower than the ninth plate 23. The ninth plate 23 is close to the fifth plate 19 and the seventh plate 21 of the second fixed platform.

[0068] Furthermore, the first plate 15, the second plate 16, and the third plate 17 each have 6 positioning holes, the fourth plate 18 has 12 positioning holes, the fifth plate 19 has 8 positioning holes, the sixth plate 20 and the seventh plate 21 each have 2 positioning holes, the eighth plate 22 has 20 positioning holes, and the ninth plate 23 has 9 positioning holes; the first plate 15, the second plate 16, and the third plate 17 each have 6 vacuum adsorption mechanisms, the fourth plate 18 has 12 vacuum adsorption mechanisms, the fifth plate 19 has 8 vacuum adsorption mechanisms, the sixth plate 20 and the seventh plate 21 each have 2 vacuum adsorption mechanisms, and the third fixed plate has a total of 18 vacuum adsorption mechanisms.

[0069] The vacuum suction cup is an accordion-style vacuum suction cup 28; the vacuum suction cup is made of rubber. The adjustment components include a height adjustment component and an angle adjustment component. The height adjustment component and the angle adjustment component allow the vacuum suction cup to be adjusted in both height and angle, thereby achieving contact between the adsorption array and the blade surface. The accordion-style vacuum suction cup is suitable for workpieces with inclined adsorption surfaces or workpieces requiring cushioning. Vacuum adsorption clamping can achieve low-stress clamping of the blade profile, and the rubber material of the suction cup can reduce damage to the workpiece surface during adsorption or release.

[0070] There are two first fixing platforms, which are spaced apart along the direction from the tenon root to the blade tip; the second fixing platform and the third fixing platform are spaced apart; there are two sets of auxiliary clamps, which are used to clamp the aero-engine blades near the blade tip and the tenon root 4, respectively. The clamp base of the first set of auxiliary clamps is located between the two first fixing platforms, and the clamp base of the second set of auxiliary clamps is located between the second fixing platform and the third fixing platform.

[0071] The attitude adjustment push rod support frame is fixedly connected to the side of the fixed platform.

[0072] The two ends of the leaf back contouring fixture 29 are connected to the fixture base 32 by a fixed pivot pin 31 and a detachable pivot pin, respectively. Both the convex surface of the leaf back contouring fixture 29 and the concave surface of the leaf basin contouring component are provided with flexible protective layers.

[0073] The mounting platform is provided with an origin coordinate hole 34 and a grid-like scale line 36, and the side of the clamping system base is provided with a transfer insertion hole 35. Considering factors such as cutting load during product processing, the base can be welded from 16Mn material, stress-annealed after welding, and finally precision-machined to ensure that the base meets the requirements of strength, rigidity, and accuracy. The scale line and origin coordinate hole are machined on the mounting platform to facilitate blade product calibration, scanning, and other work. The transfer insertion hole facilitates tooling transportation and handling.

[0074] After installing the aero-engine composite blade clamping system designed in this invention, the flexible positioning point array of the positioning unit compares the actual profile data obtained by the measurement system with the theoretical model to obtain the blade's surface deviation and vertical deviation, as well as the maximum contour error of the tenon root. Based on the maximum permissible error of the blade body machining and the maximum permissible contour error of the tenon root, and ensuring that the tenon root meets the theoretical CNC machining pose and the blade surface does not exceed the tolerance, the adjustable pose of the blade body is determined. After adjusting the positions of each positioning push rod, the blade is placed on the aero-engine composite blade clamping system designed in this invention, so that its positioning point array can be aligned with... Figure 1 The curved surfaces of the blades to be processed fit together.

[0075] The actual pose of the blade after manual placement is measured, and the pose error between the blade and the support matrix is ​​measured. Based on this error, the adjustment amount of each axis is calculated, and the flexible attitude adjustment push rod is further finely adjusted to achieve a perfect match between the pose of the blade and the positioning matrix. There is no clamping device between the front end of the flexible push rod and the blade; the contact between the two is in a free state. Adjustment will not cause blade deformation, but only change the blade's pose, as shown in the figure. Figure 2 As shown.

[0076] The system determines whether to fine-tune the blades by controlling the positioning array based on the support force feedback from the force sensors. This ensures uniform force distribution and rigid support contact with the blades, preventing excessive force at any single point. The specific method is as follows:

[0077] Step S1: Based on the data such as support force collected from the positioning point array, there are flexible support units a and b. The schematic diagram of the support force coupling relationship between a and b is shown below. Figure 14 As shown, when a is controlled to perform an axial extension motion of a certain distance, the force dataset collected for a and b is X = {X1, X2, ..., Xb}. n} and Y = {Y1,Y2,...,Y} n Sort X and Y simultaneously in ascending or descending order to obtain two sorted sets of elements x = {x1, x2, ..., xy}. n} and y = {y1, y2, ..., y n}, for each element X in set X i Let the position of the element in set x be denoted as a. i To set each element Y in set Y i Let b be the position of the element in set y. i This yields the ranking sets a and b corresponding to X and Y. Subtracting each element in sets a and b yields the ranking difference set d, where d... i =a i -b i .

[0078] Step S2: The Spearman correlation coefficient between X and Y can be obtained from d, and the calculation formula is shown in equation (1).

[0079]

[0080] r s The value range of r is [-1, 1]. s The closer the absolute value of r is to 1, the closer the data sample sets X and Y are to being perfectly monotonically correlated. s When r = 0, it indicates that X and Y are negatively correlated; that is, when r = 0, it indicates that X and Y are negatively correlated. s When r > 0, it indicates that X and Y are positively correlated; when r s When the value is 0, it indicates that X and Y are completely uncorrelated. When the support force of a certain positioning unit is too large, a positioning unit that is negatively correlated with its force (i.e., the Spearman correlation coefficient is less than zero) is selected for adjustment to reduce the support force of that positioning unit.

[0081] The least squares method is a common approach for solving curve fitting problems. It aims to minimize the sum of squared errors and calculates the polynomial regression model that best fits the sample data.

[0082] Suppose there exists a sample dataset (x) i ,y i (i = 0, 1, ..., m), let its fitting function be Equation (2).

[0083]

[0084] n is the maximum order of the fitted function; θ j (j=0,1,…,n) are the coefficients of the polynomial. Then the sum of squared errors of the fitted function can be obtained as equation (3).

[0085]

[0086] Due to the coefficients θ j To minimize the sum of squared errors S, S modulo the coefficients θ of each polynomial. j The partial derivatives should satisfy equations (4) and (5).

[0087]

[0088] The coefficients θ of the fitted function f can be obtained from equation (5). j The fitting calculation is complete.

[0089] During the fine-tuning of the positioning matrix, there is a nonlinear relationship between the supporting force of a positioning unit and the displacement of its coupled positioning unit, which can be expressed as in equation (6).

[0090]

[0091] In the formula, F1 represents the supporting force of the target positioning unit that needs to be adjusted; x0 represents the displacement of the target positioning unit coupled with the positioning unit. This invention uses the least squares method to establish a mathematical model of force coupling between positioning units, with the displacement of the coupled positioning unit as input and the force on the target positioning unit as output.

[0092] The pose influence coefficient is calculated based on the workpiece's center of mass motion data. Finally, the least squares method is used to establish a force coupling mathematical model between the positioning unit's support force and the negatively correlated force-coupled axial displacement. The calculation method for the positioning unit's pose influence coefficient on the workpiece is defined as shown in equation (7).

[0093]

[0094] In the formula, Δx is the displacement of the workpiece on the x-axis (mm); Δy is the displacement of the workpiece on the y-axis (mm); Δz is the displacement of the workpiece on the z-axis (mm); and Δd represents the fine-tuning distance of the positioning unit (mm).

[0095] Step S3: Obtain the force conditions of each positioning unit during the actual positioning process using force sensors, and determine the positioning units that require force compliance control (hereinafter referred to as overload axes) and the positioning units approaching the maximum force threshold (hereinafter referred to as overload warning axes).

[0096] Step S4: Support Force Coordination Control; First, the optimal adjustment axis is determined through three rounds of screening. Round 1: Overload warning axes in the coupled axis array are searched and eliminated. Round 2: Positioning units in the coupled axis array with a positive correlation coefficient to the overload warning axes are searched and eliminated to prevent the addition of new overload axes during adjustment. Round 3: The required displacement of the positioning units in the coupled axis array is calculated based on the force coupling mathematical model established in Step 2. To minimize the impact on the workpiece pose, the positioning unit with the smallest product of displacement and pose influence coefficients is selected as the optimal adjustment axis. Then, the optimal adjustment axis is controlled to move axially according to the displacement calculated by the mathematical model. After each force coordination control, the overload axis status of the positioning point array is checked. If the overload axis is not cleared, the overload axis and warning axis are updated according to the current force state of the positioning point array, and a new force coordination control is performed.

[0097] Step S5: Detect the overload axis of the positioning matrix and determine whether the overload axis has been cleared. If the overload axis has not been cleared, return to S3 according to the current force state of the positioning matrix. If the overload axis has been cleared, the matrix support force coordination control method has been completed.

[0098] At this point, the blade's position and support force are maintained in an ideal state. The vacuum adsorption mechanism holds the blade tightly, and the blade processing begins. Through the clamping system and lattice support force control method in this invention, blades of the same model maintain the same clamping state. Therefore, existing CNC machining toolpaths are applicable to blades of the same model, thereby avoiding the complex operation of re-scanning, recalculating, modeling, and planning CNC machining toolpaths due to position changes. At the same time, it can meet multiple processes in the manufacturing of composite blades, such as blade edge and tenon root processing, simplifying the processing process of aero-engine composite blades and improving the processing efficiency and quality of composite blades.

Claims

1. An aircraft engine composite blade clamping system, comprising: It includes support module, positioning module and clamping module, the support module includes clamping system base and fixed table, the upper surface of the clamping system base is the installation platform, the fixed table is fixedly installed on the installation platform, and the upper surface of the fixed table is provided with a positioning hole;The positioning module includes a flexible positioning point array and a flexible posture adjusting push rod, the flexible positioning point array includes a positioning unit installed in each positioning hole respectively, each positioning unit includes a vertically arranged ball head push rod and a push rod driving mechanism for driving the ball head push rod to move up and down, the upper end of the ball head push rod has a spherical end for abutting against the aero-engine blade, and the spherical end is used to extend out of the positioning hole, the flexible posture adjusting push rod includes a push rod body located in the circumferential direction of the aero-engine blade and a push rod body driving member for driving the push rod body to move towards the aero-engine blade, the front end of the push rod body close to the leading edge, trailing edge and tip of the aero-engine blade is provided with a chuck, and the chuck is used for clamping the edge of the aero-engine blade, the push rod body close to the tenon of the aero-engine blade is provided with a pushing head for pushing the tenon, the support module is fixed with a posture adjusting push rod support frame, and the push rod body driving member is fixed on the posture adjusting push rod support frame;The clamping module includes a vacuum suction mechanism and an auxiliary clamp, the vacuum suction mechanism includes a vacuum chuck and a fixing member, the fixing member is used for fixedly connecting to the fixed table, and an adjusting assembly for adjusting the height and angle of the vacuum chuck is connected between the fixing member and the vacuum chuck;The vacuum suction mechanism is arranged outside the positioning unit, and there is at least one positioning unit outside the periphery of one vacuum suction mechanism, and there is at least one positioning unit between adjacent two vacuum suction mechanisms;The auxiliary clamp includes a clamp base, a blade back profiling member and a blade basin profiling member, the clamp base is fixed on the clamping system base, the two ends of the blade back profiling member are connected to the clamp base respectively, the two ends of the blade back profiling member are located outside the leading edge and trailing edge of the aero-engine blade respectively, the two ends of the blade back profiling member and the blade basin profiling member are connected together through detachable connecting members, the blade back profiling member has a concave surface matching the back surface of the aero-engine blade, the blade basin profiling member has a convex surface matching the front surface of the aero-engine blade, the convex surface of the blade back profiling member and the concave surface of the blade basin profiling member match the back surface and front surface of the aero-engine blade respectively, and the blade back profiling member and the blade basin profiling member are connected together to clamp and position the aero-engine blade.

2. The aircraft engine composite blade clamping system of claim 1, wherein, The positioning unit is vertically installed in the positioning hole, and the positioning unit is sequentially provided with the following components from top to bottom: ball head push rod, dust cover, force sensor, sliding table assembly, ball screw, screw nut, screw box seat, worm and gear reducer, servo motor, encoder and limit switch, the movement of each positioning unit is independently controlled or linked control with other positioning units.

3. The aircraft engine composite blade clamping system of claim 1, wherein, The fixing table has three, three fixing tables are first fixing table, second fixing table and third fixing table from the direction of the tenon root of the aero-engine blade to the blade tip, the first fixing table has first table plate, second table plate and third table plate, the first table plate is parallel to the horizontal plane and close to the blade leading edge, the second table plate and the third table plate are both inclined surfaces inclined downward from the blade trailing edge to the leading edge, and the second table plate is lower than the third table plate; the second fixing table is provided with fourth table plate, fifth table plate, sixth table plate and seventh table plate, the fourth table plate and the fifth table plate are both parallel to the horizontal plane, the fourth table plate is close to the blade leading edge, the fifth table plate is located in the middle and is higher than the fourth table plate, the sixth table plate and the seventh table plate are both inclined surfaces close to the blade trailing edge, the sixth table plate and the seventh table plate are both inclined downward from the blade trailing edge to the leading edge, and the seventh table plate is lower than the sixth table plate; the third fixing table has eighth table plate and ninth table plate, the eighth table plate and the ninth table plate are both parallel to the horizontal plane, the eighth table plate is lower than the ninth table plate, and the ninth table plate is close to the fifth table plate and the seventh table plate of the second fixing table.

4. The aircraft engine composite blade clamping system of claim 3, wherein, The positioning holes on the first table plate, the second table plate and the third table plate are all 6, the positioning holes on the fourth table plate are 12, the positioning holes on the fifth table plate are 8, the positioning holes on the sixth table plate and the seventh table plate are both 2, the positioning holes on the eighth table plate are 20, and the positioning holes on the ninth table plate are 9; the vacuum suction mechanisms on the first table plate, the second table plate and the third table plate are all 6, the vacuum suction mechanisms on the fourth table plate are 12, the vacuum suction mechanisms on the fifth table plate are 8, the vacuum suction mechanisms on the sixth table plate and the seventh table plate are both 2, and the vacuum suction mechanisms on the third fixing table are 18 in total; the vacuum chuck adopts an organ type vacuum chuck; the vacuum chuck is made of rubber.

5. The aircraft engine composite blade clamping system of claim 3, wherein, The first fixing table has two, two first fixing tables are arranged at intervals along the direction from the tenon root to the blade tip; the second fixing table and the third fixing table are arranged at intervals; the auxiliary clamp has two groups, two groups of auxiliary clamps are used for clamping the aero-engine blade close to the blade tip and the tenon root, respectively, the clamp base of the first group of auxiliary clamps is located between the two first fixing tables, and the clamp base of the second group of auxiliary clamps is located between the second fixing table and the third fixing table; the posture adjusting push rod support frame is fixedly connected to the side surface of the fixing table.

6. The aircraft engine composite blade clamping system of claim 1, wherein, Both ends of the blade back profiling part are connected to the clamp base through a fixed rotating pin and a detachable rotating pin, respectively, and a flexible protective layer is arranged on the convex surface of the blade back profiling part and the concave surface of the blade basin profiling part.

7. The aircraft engine composite blade clamping system of claim 1, wherein, The installation table surface is provided with an original point coordinate hole and grid-shaped scale graduation lines, and the side surface of the clamping system base is provided with a transfer insertion hole.

8. The method of claim 1, wherein the method further comprises: determining a target support force for each of the plurality of support members; and adjusting the support force of each of the plurality of support members to the target support force. The dot array support force control method of the aero-engine composite blade clamping system comprises the following steps: S1: multi-dot array positioning motion data acquisition; first, control each positioning unit to perform axial fine adjustment in sequence, without damaging the relative stable state of the workpiece, and other positioning units remain stationary during the fine adjustment; then, record the displacement of the positioning unit, the support force and the spatial motion of the mass center of the workpiece during the fine adjustment; S2: motion data processing; the motion data processing comprises the following steps: S201: calculating Spearman correlation coefficients of each positioning unit with other positioning units according to the support force data recorded in S1; S202: calculating a pose influence coefficient according to the centroid motion data of the workpiece; S203: establishing a force coupling mathematical model between the support force of the positioning unit and the displacement of the negative correlation force coupling axis by using the least square method; S3: obtaining current force information of the positioning array; the force sensor is used to obtain the force of each positioning unit in the actual positioning process, and the positioning units that need to be subjected to force compliance control and the positioning units close to the maximum force critical value are determined; S4: support force coordination control; the support force coordination control comprises the following steps: S401: finding overload warning axes in the coupling axis array and excluding these units; S402: finding positioning units with positive correlation coefficients with the overload warning axes in the coupling axis array and excluding these units to prevent new overload axes from being added in the adjustment process; S403: calculating the displacement of the positioning units in the coupling axis array that need to move according to the force coupling mathematical model established in S2, and selecting the positioning unit with the smallest product of the displacement and the pose influence coefficient as the optimal adjustment axis in order to minimize the influence on the pose of the workpiece, and then controlling the optimal adjustment axis to move axially according to the calculated displacement; S5: detecting the overload axis condition of the positioning array, judging whether the overload axis is cleared or not, if the overload axis is not cleared, returning to S3 according to the current force state of the positioning array, and if the overload axis is cleared, the support force coordination control method of the positioning array is executed.

9. The method of claim 8, wherein the method further comprises: determining a target support force for each of the plurality of lattice supports; and adjusting the support force of each of the plurality of lattice supports to the target support force. S2 uses Spearman correlation coefficient to calculate and evaluate the correlation of support force between positioning units; when the control a performs a certain distance of axial stretching movement, the force data set collected for a and b is X={X1, X2,..., X n} and Y={Y1, Y2,..., Y n}, X and Y are sorted in ascending order or descending order, and two sorted element sets x={x1, x2,..., x n} and y={y1, y2,..., y n} are obtained, the position of each element X i in set X is recorded as a i , and the position of each element Y i in set Y is recorded as b i , and the ranking sets a and b corresponding to X and Y are obtained; the ranking difference set d is obtained by subtracting each element in set a from set b, where d i =a i -b i , and the Spearman correlation coefficient between X and Y can be obtained from d, and the calculation formula is as follows: wherein r s r s The absolute value of r s The closer the absolute value of r s to 1, the closer the data sample sets X and Y are to being perfectly monotonic. When r s < 0, X and Y are negatively correlated. When r s > 0, X and Y are positively correlated. When r s = 0, X and Y are completely uncorrelated. When the support force of a positioning unit is too large, the positioning unit with negative correlation with the force, i.e., the Spearman correlation coefficient is less than zero, is selected for adjustment to reduce the support force of the positioning unit.

10. The method of claim 8, wherein the method further comprises: determining a force of the plurality of dots; and adjusting the force of the plurality of dots based on the determined force. The method for establishing the force coupling mathematical model between the support force of the positioning unit and the displacement of the force coupling axis according to step S203 is as follows: assuming that there is a sample data set (x i ,y i )(i=0,1,…,m), and assuming that the fitting function is as follows: wherein n is the maximum order of the fitting function; θ j (j = 0, 1, …, n) are the coefficients of each term of the polynomial; and the error sum of squares of the fitting function is obtained as follows: Since the coefficients θ j The partial derivatives of S with respect to the polynomial coefficients θ j should satisfy the following two equations: From the above equation, the coefficients θ of the fitting function f can be solved j , the fitting calculation is completed; In the fine adjustment process of the positioning array, the support force of a positioning unit and the displacement of the coupled positioning unit have a nonlinear relationship, which can be expressed as the following formula In the formula, F1 is the support force of the target positioning unit that needs to be adjusted; x0 is the displacement of the coupled positioning unit of the target positioning unit, so the input quantity of the force coupling mathematical model between the support force of the positioning unit and the displacement of the negative correlation force coupling axis described in step S203 is the displacement of the positioning unit, and the output quantity is the force of the target positioning unit; The calculation method of the pose influence coefficient of the positioning unit on the workpiece is defined as the following formula: In the formula, Δx is the displacement of the workpiece in the x-axis; Δy is the displacement of the workpiece in the y-axis; Δz is the displacement of the workpiece in the z-axis; and Δd represents the fine adjustment distance of the positioning unit.

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