Special-shaped curved surface weight reduction processing method based on binocular structured light 3D measurement

Abstract

The invention discloses a special-shaped curved surface weight reduction processing method based on binocular structured light 3D measurement, relates to the technical field of 3D image data processing, is used for weight reduction processing of an external curved surface of a bent pipe, breaks through the limitation of a traditional weight reduction technology based on a binocular structured light 3D measurement technology in combination with a double-high-pressure water jet cutter, realizes a non-contact processing mode, and improves the processing efficiency. The dependence on the geometrical shape of a workpiece is reduced, and a new weight reduction solution is provided for aerospace parts with complex shapes; through high-precision 3D measurement and modeling, on the basis of scanning identification blocks, an ICP registration algorithm is adopted, complex parts are accurately reconstructed, and in combination with performance parameters of the double-high-pressure water jet cutter, accurate data support is provided for subsequent weight reduction path planning, so that the weight reduction process is more accurate; by means of the method that the inner half pipe and the outer half pipe are welded into the whole bent pipe and then the whole bent pipe is subjected to weight reduction, deformation possibly generated in the weight reduction process is effectively avoided, and the dimensional stability and precision of a part obtained after weight reduction are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D image data processing, and in particular to a method for weight reduction processing of a special-shaped curved surface based on binocular structured light 3D measurement. Background Art

[0002] The rocket engine elbow is a bent pipe that is shaped like a teapot spout, with one end small and the other end large. It is made of super-hard alloy, which has significantly greater hardness and density than steel, and is difficult to process. Due to the requirements of flow diversion, the inner wall of the elbow needs to be high-precision, smooth and flawless. Therefore, during manufacturing, a mold-forging process is used. Specifically, the calcined alloy plate is attached to the inner mold, and the alloy plate is gradually completely covered with the inner mold through forging. After demolding, a special-shaped half-tube is obtained. On the one hand, the forging process strengthens the structural strength of the half-tube, and on the other hand, the inner mold can make the half-tube obtain a precise inner wall curved surface morphology. The expected elbow is divided into two half-tubes, and the two half-tubes are processed according to the above process respectively, and then the two half-tubes are welded together to obtain the expected elbow.

[0003] However, since forging cannot guarantee the shape accuracy, the outer surface of the elbow has a finishing allowance compared with the outer surface expected by the design, and its shape is inconsistent in thickness. Therefore, it is necessary to perform weight reduction processing on the outer surface of the elbow, that is, finishing processing, to make it close to the design expectation. The existing technology usually uses a five-axis CNC machining center to directly cut the outer surface of the elbow, which is time-consuming and labor-intensive. It usually takes 7 days to complete a set of elbows, and the processing cost is high. Since the elbow is made of super-hard alloy, it is particularly time-consuming to use tools. The tool loss cost of processing a elbow can usually reach 20,000 yuan.

[0004] Based on the above background, the use of dual high-pressure water jets to replace machining centers will avoid high tool wear costs, while improving machining efficiency and reducing total machining costs. However, as a new method of weight reduction processing for pipe bending, supporting processing methods need to be developed to give full play to the advantages of dual high-pressure water jet weight reduction processing.

[0005] Through binocular structured light 3D measurement, the morphology of the special-shaped surface on the outer surface of the bent pipe can be accurately mapped. The morphology data of the special-shaped surface can be aligned with the design expectations by combining the ICP algorithm, and the processing allowance of each area on the special-shaped surface can be obtained. This can be used as a reference, combined with the processing parameters of the dual high-pressure water jet, combined with robot offline programming and simulation processing simulation, to obtain a new weight reduction processing method. Summary of the invention

[0006] The purpose of the present invention is to provide a method for weight reduction processing of rocket engine bent pipe special-shaped surfaces based on binocular structured light 3D measurement, combined with ICP registration algorithm, and applied dual high-pressure water jet processing.

[0007] In view of the above technical problems, the technical solution adopted by the present invention is: a method for weight reduction processing of special-shaped curved surfaces based on binocular structured light 3D measurement, which is used for weight reduction processing of the outer curved surface of a bent pipe, wherein the bent pipe is composed of two half pipes, and comprises the following steps: Step S1: The half-tube is clamped and fixed based on the inner surface of the half-tube, and a convex hemispherical scanning and recognition block is provided on the fixture; the equidistant surface of the inner surface of the half-tube is a track surface, and a binocular structured light 3D measurement camera is driven by a six-degree-of-freedom robotic arm to move along the track surface to scan and obtain global point cloud data of the outer surface of the half-tube and the scanning and recognition block; Step S2: Establish a standard three-dimensional model of the half-tube and its fixture, obtain the target point cloud data of the half-tube external surface and the scanning recognition block, perform point cloud registration on the global point cloud data of the scanning recognition block and the target point cloud data by using the ICP algorithm, and calculate the difference between the global point cloud data of the half-tube external surface and the target point cloud data based on the point cloud registration result, that is, the thinning amount of the half-tube weight reduction processing; Step S3: performing double high-pressure water jet cutting operations on two side surfaces of the current half pipe that are in contact with the other half pipe, and obtaining a welding groove by driving a six-degree-of-freedom robot arm; Step S4: performing the operations of steps S1 to S3 on the two half pipes respectively, and then welding the two half pipes into one bent pipe; Step S5: Set i =1,2; i The inner curved surface of the first half pipe is used as the reference to clamp and fix the bent pipe. i After the thinning amount of the first half pipe is simulated by robot offline programming and simulation, the six-degree-of-freedom robot arm drives the dual high-pressure water jet along the first half pipe. i The trajectory surface movement of the half pipe gradually completes the i The outer curvature of the half-pipe reduces weight; Step S6: inspect the processed outer surface of the elbow and perform local trimming on abnormal parts until the outer surface morphology of the elbow fully meets the target requirements.

[0008] Furthermore, the binocular structured light 3D measurement camera adopts fringe coded structured light or speckle structured light.

[0009] Furthermore, the first half-tube is the outer half-tube, and the trajectory surface of the outer half-tube is the outer virtual surface; the second half-tube is the inner half-tube, and the trajectory surface of the inner half-tube is the inner virtual surface; the global point cloud data of the outer surface of the outer half-tube obtained through the outer virtual surface is analyzed and processed, and discretized into m points to be processed; the global point cloud data of the outer surface of the inner half pipe obtained through the inner virtual surface is analyzed and processed, and discretized into npoints to be processed; the areas of all the points to be processed are the same, and the area values ​​of the points to be processed are smaller than the jet cross-sectional area of ​​the double high-pressure water jet.

[0010] Further, m + n The value of is between 12000 and 30000.

[0011] Furthermore, the average thinning amount in each area of ​​the to-be-processed point is calculated, and the processing parameters of the dual high-pressure water jet are determined based on the average thinning amount.

[0012] Furthermore, the dual high-pressure water jet is a water-gas-solid mixed water jet driven by high-pressure water and high-pressure gas, and abrasive particles are doped in the high-pressure water; the jet cross-section of the dual high-pressure water jet is circular, and the diameter of the circle is between 25 mm and 27 mm.

[0013] Furthermore, the weight loss removal per unit time of the dual high-pressure water jet is assumed to be Q , in mm³ / s, then: ; In the formula, K It is a comprehensive coefficient, which is calibrated through trial processing experiments according to the material of the bent pipe; is the volume fraction of high-pressure water, that is, the volume proportion of high-pressure water in the unit volume of the water jet; is the volume fraction of abrasive particles, that is, the volume proportion of abrasive particles in a unit volume of water jet; is the density of high-pressure water, in kg / m³; is the density of abrasive particles, in kg / m³; d is the jet cross-sectional diameter of the dual high-pressure water jet, in m; is the pressure of high-pressure water, in MPa; is the pressure of high pressure gas, in MPa; is the impact angle, which is the angle between the jet of the double high-pressure water jet and the surface normal vector of the jet action point, and the unit is rad; n is the impact angle sensitivity coefficient, which is calibrated through trial processing experiments based on the material of the bent pipe; H is the hardness of the bent pipe material, in HV; the average thinning amount and weight reduction removal amount in any area to be processed Q , the residence time of the dual high-pressure water jets in the current processing point area can be calculated, and the processing parameters can be determined by combining the robot offline programming and simulation processing.

[0014] Furthermore, the pressure of the high-pressure water is 1-50 MPa.

[0015] Furthermore, the pressure of the high-pressure gas is 0.6-1.2 MPa.

[0016] Furthermore, the solid-liquid ratio of the abrasive particles to the high-pressure water is in the range of 1:0.5 to 1:10.

[0017] Compared with the prior art, the present invention has the following advantages: (1) Based on binocular structured light 3D measurement technology and combined with dual high-pressure water jets, it breaks through the limitations of traditional weight reduction technology, realizes non-contact processing, reduces the dependence on the geometric shape of the workpiece, and provides a new weight reduction solution for complex-shaped aerospace components; (2) Through high-precision 3D measurement and modeling, based on scanning recognition blocks, and using ICP registration algorithm, complex components are accurately reconstructed, and combined with the performance parameters of dual high-pressure water jets, accurate data support is provided for subsequent weight reduction path planning, making the weight reduction process more accurate; (3) By first welding the inner half pipe and the outer half pipe into a whole, the inner half pipe and the outer half pipe are welded together to form a whole. The method of bending the tube and then reducing the weight of the whole tube effectively avoids the deformation that may occur during the weight reduction process and improves the dimensional stability and precision of the parts after weight reduction; (4) The dual high-pressure water jet uses a dual power mode of high-pressure water and high-pressure gas coupling to improve the abrasive utilization rate, introduce the influencing factor of the cavitation effect, significantly improve the peeling force, and reduce dust pollution by 95% while improving processing efficiency, thus realizing a green and environmentally friendly weight reduction processing method; (5) It eliminates the tool loss cost in traditional weight reduction technology and greatly shortens the weight reduction processing period. Compared with the 7-day processing period of traditional weight reduction technology, the processing period of the technology of the present invention is only 1.5 to 2 days. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the weight reduction processing method of the present invention.

[0019] Figure 2 It is a schematic diagram of the elbow structure of the present invention.

[0020] Figure 3 It is a schematic diagram of the outer half-tube structure of the present invention.

[0021] Figure 4 It is a schematic diagram of the inner half-tube structure of the present invention.

[0022] Figure 5 Schematic diagram of the measurement principle of the binocular structured light 3D measurement camera of the present invention.

[0023] In the figure: 1-bend pipe; 2-virtual surface; 101-outer half pipe; 102-inner half pipe; 201-outer virtual surface; 202-inner virtual surface. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods, wherein the accompanying drawings are only used for exemplary descriptions and represent only schematic diagrams rather than actual drawings, and should not be understood as limiting the present invention; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0025] like Figure 1 As shown, a method for weight reduction processing of a special-shaped curved surface based on binocular structured light 3D measurement is used for weight reduction processing of the outer curved surface of a curved pipe 1, where the curved pipe 1 consists of two half pipes, and includes the following steps: Step S1: The half-tube is clamped and fixed based on the inner surface of the half-tube, and a convex hemispherical scanning and recognition block is provided on the fixture; the equidistant surface of the inner surface of the half-tube is a track surface, and a binocular structured light 3D measurement camera is driven by a six-degree-of-freedom robotic arm to move along the track surface to scan and obtain global point cloud data of the outer surface of the half-tube and the scanning and recognition block; Step S2: Establish a standard three-dimensional model of the half-tube and its fixture, obtain the target point cloud data of the half-tube external surface and the scanning recognition block, perform point cloud registration on the global point cloud data of the scanning recognition block and the target point cloud data by using the ICP algorithm, and calculate the difference between the global point cloud data of the half-tube external surface and the target point cloud data based on the point cloud registration result, that is, the thinning amount of the half-tube weight reduction processing; Step S3: performing double high-pressure water jet cutting operations on two side surfaces of the current half pipe that are in contact with the other half pipe, and obtaining a welding groove by driving a six-degree-of-freedom robot arm; Step S4: performing the operations of steps S1 to S3 on the two half pipes respectively, and then welding the two half pipes into a bent pipe 1; Step S5: Set i =1,2; i The inner curved surface of the first half pipe is used as the reference to clamp and fix the elbow 1. i After the thinning amount of the first half pipe is simulated by robot offline programming and simulation, the six-degree-of-freedom robot arm drives the dual high-pressure water jet along the first half pipe. i The trajectory surface movement of the half pipe gradually completes the i The outer curvature of the half-pipe reduces weight; Step S6: inspect the processed outer surface of the elbow 1 and perform local trimming on abnormal parts until the outer surface morphology of the elbow 1 fully meets the target requirements.

[0026] The binocular structured light 3D measurement camera uses fringe coded structured light or speckle structured light. In this embodiment, fringe coded structured light is used, and its principle schematic diagram is as follows: Figure 5 shown.

[0027] like Figure 2 , Figure 3 and Figure 4 As shown, the first half-tube is the outer half-tube 101, and the trajectory surface of the outer half-tube 101 is the outer virtual surface 201; the second half-tube is the inner half-tube 102, and the trajectory surface of the inner half-tube 102 is the inner virtual surface 202; the outer virtual surface 201 and the inner virtual surface 202 together constitute the virtual surface 2; the global point cloud data of the outer surface of the outer half-tube 101 obtained through the outer virtual surface 201 is analyzed and processed, and discretized into m The global point cloud data of the outer surface of the inner half pipe 102 obtained by the inner virtual surface 202 is analyzed and processed, and discretized into n points to be processed; the areas of all the points to be processed are the same, and the area values ​​of the points to be processed are smaller than the jet cross-sectional area of ​​the double high-pressure water jet; m + n The value of is between 12000 and 30000. In this embodiment, m The value is 8800. n The value is 4600; further, by calculating the average thinning amount in each area of ​​the processing point, the processing parameters of the double high-pressure water jet are determined according to the average thinning amount; specifically, the double high-pressure water jet is a water-gas-solid mixed water jet driven by high-pressure water and high-pressure gas, and abrasive particles are doped in the high-pressure water; the jet cross section of the double high-pressure water jet is a circle, and the diameter of the circle is d Between 25mm and 27mm; Assume that the weight reduction removal per unit time of the double high-pressure water jet is Q , in mm³ / s, then: ; In the formula, K It is a comprehensive coefficient, which is calibrated through trial processing experiments based on the material of the elbow 1; is the volume fraction of high-pressure water, that is, the volume proportion of high-pressure water in the unit volume of the water jet; is the volume fraction of abrasive particles, that is, the volume proportion of abrasive particles in a unit volume of water jet; is the density of high-pressure water, in kg / m³; is the density of abrasive particles, in kg / m³; is the pressure of high-pressure water, in MPa; is the pressure of high pressure gas, in MPa; is the impact angle, which is the angle between the jet of the double high-pressure water jet and the surface normal vector of the jet action point, and the unit is rad; n is the impact angle sensitivity coefficient, which is calibrated through trial processing experiments according to the material of the elbow 1 and is usually between 1 and 2; His the hardness of the material of the bend 1, in HV; the average thinning amount and weight reduction removal amount in any area to be processed Q , the residence time of the dual high-pressure water jet in the current processing point area can be calculated. Specifically, assuming that the average thinning amount of a certain point is 1mm and the jet cross-sectional area of ​​the dual high-pressure water jet is 507mm², the total volume of material to be removed at this point is 507mm³. Assuming that it is 90°, Q The calculated value is 507 mm³ / s, so the residence time of the double high-pressure water jet at this point is 1 s, which can remove 507 mm³ of material. Based on the above method, combined with robot offline programming and simulation processing, Q In the value calculation formula, when other parameters except the impact angle have been set, the weight loss processing parameters are determined, including path planning, the impact angle at any point on the path, and the jet residence time at any point on the path.

[0028] Based on the different materials, in this embodiment, the pressure of high-pressure water is usually set in the range of 1-50MPa, the pressure of high-pressure gas is usually set in the range of 0.6-1.2MPa, and the solid-liquid ratio of abrasive particles to high-pressure water is usually set in the range of 1:0.5 to 1:10; in particular, assuming that the solid-liquid ratio of abrasive particles to high-pressure water is 1:4, then The value of is 0.8. The value of is 0.2.

Claims

1. A method for weight reduction processing of a special-shaped curved surface based on binocular structured light 3D measurement, which is used for weight reduction processing of the outer curved surface of a curved pipe (1), wherein the curved pipe (1) consists of two half pipes and is characterized in that: The following steps are involved: Step S1: The half-tube is clamped and fixed based on the inner surface of the half-tube, and a convex hemispherical scanning and recognition block is provided on the fixture; the equidistant surface of the inner surface of the half-tube is a track surface, and a binocular structured light 3D measurement camera is driven by a six-degree-of-freedom robotic arm to move along the track surface to scan and obtain global point cloud data of the outer surface of the half-tube and the scanning and recognition block; Step S2: Establish a standard three-dimensional model of the half-tube and its fixture, obtain the target point cloud data of the half-tube external surface and the scanning recognition block, perform point cloud registration on the global point cloud data of the scanning recognition block and the target point cloud data by using the ICP algorithm, and calculate the difference between the global point cloud data of the half-tube external surface and the target point cloud data based on the point cloud registration result, that is, the thinning amount of the half-tube weight reduction processing; Step S3: performing double high-pressure water jet cutting operations on two side surfaces of the current half pipe that are in contact with the other half pipe, and obtaining a welding groove by driving a six-degree-of-freedom robot arm; Step S4: performing the operations of steps S1 to S3 on the two half pipes respectively, and then welding the two half pipes into a bent pipe (1); Step S5: Set i =1,2; i The inner curved surface of the first half pipe is used as a reference to clamp and fix the bent pipe (1). i After the thinning amount of the first half pipe is simulated by robot offline programming and simulation, the six-degree-of-freedom robot arm drives the dual high-pressure water jet along the first half pipe. i The trajectory surface movement of the half pipe gradually completes the i The outer curvature of the half-pipe reduces weight; Step S6: inspecting the outer surface of the processed curved pipe (1) and performing local trimming on abnormal parts until the outer surface morphology of the curved pipe (1) completely meets the target requirements.

2. The method for weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 1, characterized in that: The binocular structured light 3D measurement camera adopts fringe coded structured light or speckle structured light.

3. The method for weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 2, characterized in that: The first half-tube is the outer half-tube (101), and the trajectory surface of the outer half-tube (101) is the outer virtual surface (201); the second half-tube is the inner half-tube (102), and the trajectory surface of the inner half-tube (102) is the inner virtual surface (202); the global point cloud data of the outer surface of the outer half-tube (101) obtained through the outer virtual surface (201) is analyzed and processed, and discretized into m points to be processed; the global point cloud data of the outer surface of the inner half pipe (102) obtained through the inner virtual surface (202) is analyzed and processed, and discretized into n points to be processed; the areas of all the points to be processed are the same, and the area values ​​of the points to be processed are smaller than the jet cross-sectional area of ​​the double high-pressure water jet.

4. The method for weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 3, characterized in that: m + n The value of is between 12000 and 30000.

5. The method for weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to any one of claims 3 or 4, characterized in that: Calculate the average thinning amount in each area of ​​the processing point, and determine the processing parameters of the double high-pressure water jet according to the average thinning amount.

6. The method for weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 5, characterized in that: The double high-pressure water jet is a water-gas-solid mixed water jet driven by high-pressure water and high-pressure gas, with abrasive particles doped in the high-pressure water; the jet cross section of the double high-pressure water jet is circular, and the diameter of the circle is between 25mm and 27mm.

7. The method for weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 6, characterized in that: Assume that the weight reduction removal per unit time of the double high-pressure water jet is Q , in mm³ / s, then: ； In the formula, K is a comprehensive coefficient, which is calibrated through trial processing experiments based on the material of the bent pipe (1); is the volume fraction of high-pressure water, that is, the volume proportion of high-pressure water in the unit volume of the water jet; is the volume fraction of abrasive particles, that is, the volume proportion of abrasive particles in a unit volume of water jet; is the density of high-pressure water, in kg / m³; is the density of abrasive particles, in kg / m³; d is the jet cross-sectional diameter of the dual high-pressure water jet, in m; is the pressure of high-pressure water, in MPa; is the pressure of high pressure gas, in MPa; The impact angle is the angle between the jet of the double high-pressure water jet and the surface normal vector of the jet action point, and the unit is rad; n is the impact angle sensitivity coefficient, which is calibrated through trial processing experiments based on the material of the elbow (1); H is the hardness of the material of the bent tube (1), in HV; the average thinning amount and weight reduction removal amount in any area to be processed Q , the residence time of the dual high-pressure water jets in the current processing point area can be calculated, and the processing parameters can be determined by combining the robot offline programming and simulation processing.

8. The method for weight reduction of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 7, characterized in that: The pressure of high-pressure water is 1-50MPa.

9. The method for weight reduction processing of a special-shaped curved surface based on binocular structured light 3D measurement according to claim 8, characterized in that: The pressure of high-pressure gas is 0.6-1.2MPa.

10. The method for weight reduction processing of special-shaped curved surfaces based on binocular structured light 3D measurement according to claim 9, characterized in that: The solid-liquid ratio of abrasive particles to high-pressure water ranges from 1:0.5 to 1:10.

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