Accurate positioning method for detecting turbine blade of aero-engine

Abstract

The invention discloses a precise positioning method for detecting an aero-engine turbine blade, and particularly relates to the technical field of aero-engine part detection. According to the method, a mechanical arm, an electric claw, a shifting clamp, a positioning clamp, a bidirectional linear module and an ultrasonic thickness measuring system are adopted for cooperative operation. The method comprises the core steps that firstly, a blade mortise is pre-clamped by a shifting clamp and moved to a positioning station; the positioning clamp driven by the bidirectional linear module is elastically attached and locked through an area array type elastic ejector pin capable of independently and elastically stretching out and drawing back, so that the blade body is accurately reshaped and fixed; then the shifting clamp is locked to fix the mortise; and finally, the blade is moved to a thickness measuring station to complete ultrasonic detection. According to the method, the blade body with the stable size serves as the positioning reference, the influence of mortise manufacturing errors is effectively eliminated through the cooperative locking strategy of the double flexible clamps, high-precision and high-repeatability positioning of blade measuring points is achieved, and the accuracy and reliability of ultrasonic thickness measuring results are guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine component testing technology, specifically relating to a precise positioning method for testing aero-engine turbine blades. Background Technology

[0002] After manufacturing, the wall thickness of aero-engine turbine blades needs to be tested, and ultrasonic thickness measurement is a commonly used non-destructive testing method. During testing, the blade needs to be positioned so that the preset measurement points can be accurately aligned with the ultrasonic probe.

[0003] Turbine blades feature complex free-form blade surfaces and precision tenons used for assembly. Currently, there are two main types of automated positioning methods. One type involves using a robotic arm to grip the tenons for transport and positioning. This method has the following problems: First, rigid gripping may damage the precision tenon mating surfaces; second, using only the tenon as a reference makes it difficult to compensate for the manufacturing tolerances of the blade itself, resulting in poor repeatability of the blade's position relative to the measuring probe. The other type uses a dedicated fixture that matches the blade profile for positioning. This method requires customized fixtures for different blade models, resulting in higher costs; and rigid clamping may cause elastic deformation of thin-walled blades, affecting the accuracy of thickness measurements. Furthermore, if the inspection process requires switching between the transport fixture and the measuring station fixture, secondary clamping errors will be introduced, affecting the overall positioning accuracy.

[0004] Therefore, a positioning method for aero-engine turbine blades is needed that can avoid damaging the blades during the inspection process, adapt to individual differences in blade profiles, achieve highly repeatable positioning, and reduce or eliminate errors caused by reference conversion. Summary of the Invention

[0005] The purpose of this invention is to provide a precise positioning method for detecting turbine blades of aero-engines.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A precise positioning method for detecting turbine blades of aero-engines is implemented using the following apparatus: The device includes a robotic arm at the end of a robotic arm; an electric gripper fixedly mounted at the end of the robotic arm; and two shifting grippers arranged in pairs and driven to open and close by the electric grippers. Each shifting gripper is a flexible gripper with an array of elastic pins at its front end that can be independently extended and retracted. Each array of elastic pins can be independently extended and retracted, and the shifting gripper is provided with a locking mechanism for simultaneously locking all the array of elastic pins. Two positioning clamps are arranged in pairs and driven to open and close by a bidirectional linear module. The positioning clamps are flexible clamps with independently elastic retractable array-type elastic pins at the front end. Each array-type elastic pin can independently elastically retract. The positioning clamps are equipped with a locking mechanism for simultaneously locking all array-type elastic pins. An ultrasonic thickness measurement system is also provided. The locking mechanism of the displacement fixture and the locking mechanism of the positioning fixture are controlled independently of each other; The method includes the following steps in sequence: S1. Material handling and pre-clamping steps: After the two displacement clamps are opened by the electric gripper, they move to the top of the blade to be inspected supported on the blade rack and move downward, so that the array of elastic pins of the displacement clamps contacts both sides of the tenon groove of the blade; in the state where the locking mechanism is not locked and the array of elastic pins can extend and retract freely, the electric gripper drives the displacement clamps to apply an initial clamping force of 5-15N to the tenon groove, and while maintaining this clamping force, the blade is moved to the positioning station; S2. Precise positioning and coordinated locking steps of the blade: At the positioning station, the two positioning fixtures are first opened by the bidirectional linear module; then, the shifting fixture carrying the blade is moved down to place the blade between the two opened positioning fixtures; then, the two positioning fixtures are moved towards each other by the bidirectional linear module, so that the array of elastic pins of the positioning fixtures contacts the surface of the blade. Each pin passively conforms to the curved surface of the blade through its own elastic extension and contraction. Then, the locking mechanism of the positioning fixture is triggered to lock all its array of elastic pins, thereby restoring and fixing the blade; subsequently, the locking mechanism of the shifting fixture is triggered to lock all its array of elastic pins, thereby fixing the tenon. S3. Transfer and thickness measurement steps: The two positioning fixtures are driven by the bidirectional linear module to move in opposite directions to detach from the blade body; the robotic arm moves the blade, which is fixed by the locked displacement fixture, to the thickness measurement station; at the thickness measurement station, the robotic arm moves each preset measurement point on the blade to below the probe of the ultrasonic thickness measurement system in sequence according to the pre-taught motion trajectory for ultrasonic thickness measurement.

[0007] Furthermore, in step S2, from the moment the array of elastic pins of the positioning fixture begins to contact the blade surface until the locking mechanism of the displacement fixture is triggered to complete the locking, the position and posture of the end of the robotic arm and the electric gripper in space remain unchanged.

[0008] Furthermore, the electric gripper is fixed to the end of the robotic arm via a robotic arm-electric gripper connector.

[0009] Furthermore, the displacement clamp is fixed to the slider of the electric gripper via an electric gripper connector.

[0010] Furthermore, the positioning fixture is fixed to the slider of the bidirectional linear module via the positioning fixture and the module connector.

[0011] Furthermore, the bidirectional linear module includes a module drive motor, which drives a forward and reverse screw to rotate, thereby causing the two sliders to move synchronously in opposite directions or in opposite directions in a linear motion.

[0012] Furthermore, in step S2, the locking mechanism of the positioning clamp is triggered during the process of the bidirectional linear module driving it to continuously clamp the blade. Specifically, the triggering condition is that the contact pressure of the positioning clamp on the blade reaches 20-30N.

[0013] Furthermore, in step S3, by controlling the robotic arm to change the posture of the blade, the measurement points located in different spatial directions of the blade are sequentially aligned with the probe of the ultrasonic thickness measurement system, ensuring that the angle between the measured surface of the measurement point and the ultrasonic probe is 90°±2°.

[0014] Furthermore, the method is used to perform cyclic operations on multiple blades in the same batch.

[0015] Beneficial effects of this invention: 1. The flexible array of elastic pins at the front end of the shifting fixture and positioning fixture of this invention can extend and retract independently before locking, adaptively conforming to the complex curved surface of the blade tenon or blade body. After conforming, the pin array is simultaneously locked by the locking mechanism, thereby fixing the blade without applying excessive concentrated stress to the local area, thus protecting the blade surface and obtaining a stable clamping posture.

[0016] 2. The method of this invention first uses a positioning clamp to adaptively fit and lock the blade, completing precise reshaping and fixation based on the blade. During this process, the shifting clamp remains in a pre-clamping state but is not locked. Subsequently, the shifting clamp is locked, holding the blade together with the positioning clamp. Afterward, the positioning clamp can be released and removed, and the blade is carried by the locked shifting clamp for subsequent operations. This process of prioritizing precise blade positioning and using tenon and groove joints for fixation ensures the consistency of the blade's positioning posture as the main measured area, avoiding secondary clamping errors caused by reference conversion.

[0017] 3. The method of this invention integrates the positioning process with the ultrasonic thickness measurement system. After the blade is precisely fixed, the robotic arm can sequentially move each measurement point to the probe according to the taught trajectory. Since the blade's positioning posture is consistent each time, the spatial position of the measurement points in batch testing has high repeatability, ensuring the comparability and stability of the test data, and is suitable for continuous testing of batch blades.

[0018] 4. By setting up a shifting gripper driven by an electric gripper at the end of the robotic arm and a positioning gripper driven by an independent linear module, and making their locking mechanisms independently controllable, a feasible hardware foundation is provided for realizing the above-mentioned collaborative operation process of pre-clamping-precision positioning-coordinated locking-positioning and removal. Each execution unit has a clear division of labor and orderly control. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the material handling station in an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the positioning station in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the thickness measurement station in an embodiment of the present invention.

[0022] In the figure: 1. End of robotic arm, 2. Connector between robotic arm and electric gripper, 3. Electric gripper, 4. Connector between electric gripper and shifting fixture, 5. Shifting fixture, 6. Blade, 7. Blade holder, 8. Positioning fixture, 9. Connector between positioning fixture and module, 10. Bidirectional linear module, 11. Module drive motor, 12. Thickness measurement system. Detailed Implementation

[0023] The preparation method of the present invention will be described in detail below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0024] Example 1 The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, but the scope of protection of the present invention is not limited thereto.

[0025] This embodiment provides a method for precisely positioning turbine blades in an aero-engine, which is executed by a specific device. The specific configuration of this device is as follows: Figures 1 to 3 As shown.

[0026] See Figure 1 The device includes a robotic arm and its end effector 1. An electric gripper 3 is fixedly mounted on the end effector 1 via a robotic arm-to-electric gripper connector 2. Two paired displacement grippers 5 are fixedly mounted on the slider of the electric gripper 3 via a displacement gripper connector 4. The displacement gripper 5 is a flexible gripper, with a set of independently elastically extendable array-type elastic pins (arranged in a matrix with a density of 4 pins / cm²) at its front end. 2 Each array of elastic ejector pins can extend and retract independently. The shifting fixture 5 is also equipped with a locking mechanism, which is a pneumatic locking pin assembly that can simultaneously lock all array of elastic ejector pins in the current position.

[0027] See also Figure 1 The device also includes a bidirectional linear module 10. Each slider of the bidirectional linear module 10 is fixedly mounted with a positioning clamp 8 via a positioning clamp and module connector 9; therefore, the positioning clamps 8 are also arranged in pairs. The bidirectional linear module 10 includes a module drive motor 11. The module drive motor 11 drives a forward and reverse screw to rotate, thereby causing the two sliders on it to move synchronously in opposite directions or in a straight line. The structure of the positioning clamp 8 is similar to that of the displacement clamp 5; its front end is also equipped with an independently elastic array of retractable elastic pins (arranged in a matrix with a density of 4 pins / cm²). 2 It is equipped with an independent locking mechanism (electromagnetic locking assembly) to simultaneously lock all its array of elastic pins. The locking mechanism of the shifting fixture 5 and the locking mechanism of the positioning fixture 8 can be independently controlled by the control system.

[0028] The device also includes an ultrasonic thickness measurement system 12, whose probe is fixedly installed at the thickness measurement station.

[0029] Based on the above device, the precise positioning method of this embodiment is executed in the following steps in sequence: The first step is material handling and pre-clamping.

[0030] like Figure 1 As shown, the robotic arm moves to the material handling station. The electric gripper 3 actuates, driving the two shifting clamps 5 to open. The robotic arm controls the shifting clamps 5 to move above the blade holder 7, and then moves them downwards, so that the array of elastic pins of the two shifting clamps 5 contact the two sides of the tenon groove of the blade 6 to be inspected. At this time, the locking mechanism of the shifting clamps 5 is in an unlocked state, and each array of elastic pins can freely extend and retract to adapt to the curved surface of the tenon groove. The electric gripper 3 then drives the two shifting clamps 5 to move towards each other, applying an initial clamping force of 8N to both sides of the tenon groove. While maintaining this clamping force, the robotic arm lifts the blade 6 from the holder 7 and moves it to the positioning station.

[0031] The second step is precise positioning and coordinated locking of the blade.

[0032] like Figure 2As shown, blade 6 is moved to the positioning station. First, the module drive motor 11 of the bidirectional linear module 10 starts, driving the two positioning clamps 8 to move in opposite directions to the open state. Then, the robotic arm carries the blade 6 held by the shifting clamp 5 downward, placing the blade body between the two open positioning clamps 8. Next, the module drive motor 11 drives in the opposite direction, causing the two positioning clamps 8 to move towards each other until the array of elastic pins at their front ends contact the blade surface. During the contact process, each array of elastic pins of the positioning clamp 8 independently elastically expands and contracts according to the shape of the blade surface, thus passively and stress-free conforming to the entire contact area. When the array of elastic pins of the positioning clamp 8 is fully conforming to the blade and the conforming pressure on the blade reaches 25N, the control system triggers the locking mechanism of the positioning clamp 8 (the electromagnetic locking assembly is electromagnetically attracted and locked), locking all the array of elastic pins simultaneously, thereby restoring and fixing the spatial shape of the blade.

[0033] It should be noted that from the moment the array of elastic pins of the positioning fixture 8 begins to contact the blade surface until the subsequent shifting fixture 5 completes locking, the position and orientation of the robotic arm end effector 1 and the electric gripper 3 remain unchanged in space. The locking action of the positioning fixture 8 can be triggered during the process of the bidirectional linear module 10 continuously applying a contact force to the blade.

[0034] After the positioning fixture 8 is locked, the control system immediately triggers the locking mechanism of the shift fixture 5, simultaneously locking all its array of elastic pins. At this point, the blade 6 is fixed to the tenon part by the shift fixture 5 and to the blade body part by the positioning fixture 8, completing the coordinated and precise fixing at the positioning station.

[0035] The third step is the transfer and thickness measurement.

[0036] like Figure 3 As shown, after the blade 6 completes precise positioning, the bidirectional linear module 10 drives the two positioning clamps 8 to move in opposite directions, causing its array-type elastic pins to detach from the blade surface. At this time, the blade 6 is completely held by the locked shift clamp 5. The robotic arm then moves the shift clamp 5 and the fixed blade 6 to the thickness measurement station. At the thickness measurement station, the robotic arm controls the movement of the blade 6 according to the pre-taught motion trajectory, sequentially moving each preset measurement point on its blade surface directly below the probe of the ultrasonic thickness measurement system 12 for ultrasonic thickness measurement. For measurement points located in different spatial directions on the blade 6, the robotic arm is controlled to change the posture of the blade 6, so that the measured surface of each measurement point maintains an optimal measurement angle of 90°±2° with the ultrasonic probe.

[0037] This method is applicable to the continuous automated inspection of multiple blades 6 in the same batch. After the inspection of one blade is completed, the device is reset, and the above steps are repeated to start the operation cycle for the next blade.

[0038] The above embodiments describe in detail the implementation process of the present invention. Those skilled in the art will understand that, without departing from the principles of the present invention, several adjustments can be made to the specific structure, control logic, or sequence of steps of the above-described device, and these adjustments should also be considered within the scope of protection of the present invention.

Claims

1. A method for precisely positioning turbine blades of an aero-engine, characterized in that, The following device is used to perform this action: The robotic arm includes a robotic arm end (1); an electric gripper (3) fixedly installed at the robotic arm end (1); and two shifting clamps (5) arranged in pairs and driven to open and close by the electric gripper (3). The shifting clamps (5) are flexible clamps with independently elastic retractable array-type elastic pins at the front end. Each array-type elastic pin can be independently elastically retracted, and the shifting clamps (5) are provided with a locking mechanism for simultaneously locking all array-type elastic pins. Two positioning clamps (8) are arranged in pairs and driven to open and close by a bidirectional linear module (10). The positioning clamps (8) are flexible clamps with independently elastic retractable array-type elastic pins at the front end. Each array-type elastic pin can be independently elastically retracted. The positioning clamps (8) are provided with a locking mechanism for simultaneously locking all array-type elastic pins. An ultrasonic thickness measurement system (12) is also provided. The locking mechanism of the shifting fixture (5) and the locking mechanism of the positioning fixture (8) are controlled independently of each other; The method includes the following steps in sequence: S1. Material picking and pre-clamping steps: After the electric claw (3) drives the two displacement clamps (5) to open, they move to the top of the blade (6) to be inspected, which is supported on the blade material rack (7) and move down, so that the array of elastic pins of the displacement clamp (5) contacts the two sides of the tenon groove of the blade (6); in the state where the locking mechanism is not locked and the array of elastic pins can extend and retract freely, the electric claw (3) drives the displacement clamp (5) to apply an initial clamping force to the tenon groove, and while maintaining the clamping force, the blade (6) is moved to the positioning station; S2, Precise positioning and coordinated locking steps of the blade: At the positioning station, the two positioning clamps (8) are first opened by the bidirectional linear module (10); then the shift clamp (5) carrying the blade (6) is driven to move down, placing the blade (6) between the two opened positioning clamps (8); then the two positioning clamps (8) are driven to move towards each other by the bidirectional linear module (10), so that the array of elastic pins of the positioning clamp (8) contacts the surface of the blade, and each pin passively fits the curved surface of the blade through its own elastic extension and contraction. Then the locking mechanism of the positioning clamp (8) is triggered to lock all its array of elastic pins, thereby restoring and fixing the blade; after that, the locking mechanism of the shift clamp (5) is triggered to lock all its array of elastic pins, thereby fixing the tenon. S3. Transfer and thickness measurement steps: The two positioning clamps (8) are driven by the bidirectional linear module (10) to move in opposite directions to detach from the blade body; the blade (6) fixed by the locked displacement clamp (5) is moved by the robotic arm to the thickness measurement station; at the thickness measurement station, the robotic arm moves each preset measurement point on the blade (6) to the probe of the ultrasonic thickness measurement system (12) in sequence according to the pre-taught motion trajectory to perform ultrasonic thickness measurement.

2. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, In step S2, from the moment the array of elastic pins of the positioning fixture (8) begins to contact the blade surface until the locking mechanism of the shift fixture (5) is triggered to complete the locking, the position and posture of the end of the robotic arm (1) and the electric gripper (3) in space remain unchanged.

3. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, The electric gripper (3) is fixed to the end of the robotic arm (1) via the robotic arm and the electric gripper connector (2).

4. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, The displacement clamp (5) is fixed to the slider of the electric gripper (3) by the electric gripper and the displacement clamp connector (4).

5. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, The positioning fixture (8) is fixed to the slider of the bidirectional linear module (10) via the positioning fixture and the module connector (9).

6. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, The bidirectional linear module (10) includes a module drive motor (11), which drives a forward and reverse screw to rotate, thereby causing the two sliders to move synchronously in opposite directions or in opposite directions in a linear motion.

7. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, In step S2, the locking mechanism of the positioning clamp (8) is triggered during the process of the bidirectional linear module (10) driving it to continuously clamp the blade.

8. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, In step S3, the posture of the blade (6) is changed by controlling the robotic arm so that the measurement points located in different spatial directions of the blade (6) are aligned with the probe of the ultrasonic thickness measurement system (12) in sequence.

9. The precise positioning method for detecting turbine blades of an aero-engine according to claim 1, characterized in that, The method is used to perform cyclic operations on multiple blades (6) in the same batch.

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