Customized catheter shape design method

Abstract

The invention discloses a customized guide pipe shape optimization design method which is used for solving the problem that a guide pipe needs to be subjected to cold calibration, filing repair or field sampling during engine assembly due to poor size consistency of a liquid rocket engine. The method comprises the following steps: firstly, measuring an engine conduit interface, then assembling a conduit sample piece and the interface as an initial state of an optimization model, taking coordinate values of each node of the conduit as variables, taking conduit similarity as a target function, taking distance, position requirements and the like between the conduit and an engine and other parts as constraint conditions, and solving by using a genetic algorithm; and obtaining coordinate values of each node of the conduit so as to obtain a complete pipe shape. According to the method, the engine conduit pipe shape meeting the requirements can be rapidly designed, the processes of shape correction, filing, field sampling and the like during engine assembly are avoided, and the conduit production precision and efficiency are improved.

Description

Technical Field

[0001] The invention relates to a customized duct tube shape optimization design, and more specifically to a customized duct tube shape optimization design method for a liquid rocket engine. Background Art

[0002] The piping system is an important component of liquid rocket engines. However, due to poor product size consistency and other reasons, a large number of batch-bent pipes cannot be matched properly. Assemblers need to use their experience to calibrate and repair the direction of the pipes and the pipe interfaces according to the actual situation of the engine, and some pipes need to be sampled on-site for bending production. The process of manual calibration and repair and on-site sampling is extremely dependent on personnel experience, labor-intensive and inefficient; secondly, manual repair or sampling will cause the direction of each pipe to be different, which is not conducive to improving the overall consistency of the engine. Therefore, the assembly of the piping system has become a bottleneck in improving the final assembly capacity of liquid rocket engines. Summary of the invention

[0003] In view of the defects and deficiencies in the above-mentioned prior art, the purpose of the present invention is to overcome the technical difficulties that the liquid rocket engine duct needs to be manually repaired or sampled. The present invention provides a duct shape optimization design method. The method first measures the engine duct interface and constraint characteristics, and then assembles the duct sample and the interface in the CAD software as the initial state of the optimization model, takes the coordinate value of each node of the duct as a variable, takes the duct similarity as the objective function, takes the distance and position requirements between the duct and the engine and other components as constraints, and uses a genetic algorithm to solve, obtains the coordinate value of each node of the duct, and thus obtains the optimal duct shape.

[0004] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0005] A customized catheter tube shape optimization design method includes the following steps:

[0006] Measurement phase: Use measurement equipment to measure the interface of the customized duct of the liquid rocket engine, the position constraint characteristics of the duct and the pre-installed components on the engine, and extract the measured data of the interface at both ends of the duct and its position constraint characteristics;

[0007] Design phase: Based on the measured data of the customized catheter interface and its position constraint features, the catheter sample is assembled and its shape is optimized to avoid interference with prefabricated components and obtain the optimal tube shape of the customized catheter.

[0008] The method of extracting measured data of the interfaces and position constraint features at both ends of the catheter comprises the following steps:

[0009] Fit the center and normal data of the cross-section circle of the interface at both ends of the catheter;

[0010] The prefabricated component is abstracted as a cylinder or a sphere, and the axis data of the cylinder and / or the center data of the sphere are extracted according to its position constraint features.

[0011] The design phase includes the following steps:

[0012] Step 1: Establish model instances of the catheter sample, the measured interface, and the position constraint feature respectively; assemble the catheter and the interface so that the straight segments at the beginning and the end of the catheter pass through the interfaces on both sides respectively; the catheter sample is the initial theoretical form of the catheter design;

[0013] Step 2: Initialize the shape of the catheter, drive the key points on the axis of the two ends of the catheter, and adjust the direction of the straight segments at both ends of the catheter so that the straight segments at both ends of the catheter are collinear with the normals of the two interfaces respectively;

[0014] Step 3: Establish a mathematical optimization model. Under the condition of satisfying spatial constraints, adjust the coordinates of the key points of the catheter to change the shape and posture of the catheter, find the optimal solution that makes the designed catheter model infinitely close to the shape of the catheter sample, and obtain the optimal tube shape;

[0015] Step 4: Output the optimal tube shape of the catheter, convert the straight tube segment angle including the tube segment extension line into a curved angle again, and establish a conventional solid model of the catheter.

[0016] The mathematical optimization model for customized catheter tube shape design includes the following steps:

[0017] 1) Design variables

[0018] The catheter shape is abstracted as a curve segment formed by connecting multiple straight line segments. If the catheter has n key points, there are n-1 straight line segments and n-2 bends.

[0019] 2) Objective Function

[0020] In order to avoid interference between the designed catheter and surrounding parts and make the designed catheter and the catheter sample as similar as possible, the catheter sample model and the optimized model are translated and rotated to make the two optimally aligned, and the mean of the position deviation of each corresponding point is taken as the similarity index and the objective function;

[0021] 3) Constraints

[0022] The length variation of each section of the catheter should be within the control range;

[0023] The spacing requirements between the duct and other prefabricated component features on the engine; the spacing requirements include two types: the distance between the duct straight segment and the point constraint feature on the engine and the distance between the duct straight segment and the axis of the prefabricated component on the engine;

[0024] The spatial constraint range of each key point coordinate.

[0025] The customized catheter tube shape design model is the following mathematical model:

[0026] Find x=(x1,x2,...,x 3(n-4)+2 )

[0027]

[0028] In the formula, x=(x1,x2,…,x 3(n-4)+2 ) is 3(n-4)+2 design variables, x 3(n-4)+2 Represents the length of the last line segment l n-1 ; The coordinates of the key point i of the catheter model after optimization, is the coordinate set P ORT The coordinates of the i-th point, P ORT is the original point coordinate set P of the catheter O The coordinate set P after adjustment with the catheter shape G Align the transformed coordinate set; where d j represents the distance between the catheter and the jth feature, d jmin Indicates the minimum required value of the distance value; d lk represents the distance between the conduit and the axis of the kth component, d ljmin Indicates the minimum required value of the spacing; x kmin and x kmax The coordinate values ​​are x k The upper and lower limits of .

[0029] The point set P after the alignment transformation ORT and the original point coordinate set P of the catheter O The transformation relationship is:

[0030] P ORT =R*P O +T

[0031] Where R represents the rotation matrix, T represents the translation matrix, and the original point coordinate set P of the catheter is O The coordinate set P after adjusting the catheter shape G Singular value decomposition (SVD) was performed to achieve the best alignment, thereby obtaining the best rigid transformation of the catheter sample and the optimized model.

[0032] The mathematical model is solved by a genetic algorithm to obtain an optimal catheter model.

[0033] The present invention has the following beneficial effects and advantages:

[0034] 1. Realize the coordinated production of liquid rocket engine ducts and improve duct production efficiency. Traditional customized duct production requires cold calibration, filing or on-site sampling, which takes a lot of time. The present invention can quickly obtain relevant parameters of the engine and automatically generate duct design solutions based on preset algorithms and models, greatly shortening the time cycle from demand to design completion.

[0035] 2. Improve the production accuracy of the duct. The present invention can perform accurate duct design based on the precise parameters of the engine, such as interface data, constraint component position, etc. It ensures that the duct is accurately matched with other components of the engine, improving the overall performance and reliability of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of measuring point cloud and feature extraction;

[0037] Figure 2 Modeling schematics for interface and constraint features;

[0038] Figure 3 It is a schematic diagram of the assembly model of the catheter sample and the interface;

[0039] Figure 4 Initialize the schematic diagram for the shape of the catheter sample;

[0040] Figure 5 Schematic diagram of the optimal catheter model;

[0041] Figure 6 This is a schematic diagram of the rounded corners of the catheter;

[0042] Figure 7 A three-dimensional schematic diagram of the catheter. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the accompanying drawings and implementation examples.

[0044] The customized duct tube shape design includes two stages: the engine feature measurement stage and the duct tube shape design stage. In the measurement stage, the liquid rocket engine duct interface features and constraint features are actually measured by measuring equipment, and feature data is provided as input data for the customized duct tube shape design system. The measuring equipment used in this method is a three-dimensional laser scanner to obtain the point cloud of the feature parts and then extract the feature data. In the design stage, the actual data of the on-site measurement is accepted, and the twin model of the duct interface and constraints is established through the secondary development of CAD software, and then the customized duct tube shape is optimized to obtain the optimal tube shape of the customized duct.

[0045] A customized catheter tube shape design method includes the following steps:

[0046] Measurement phase: Figure 1As shown, a laser scanning device is used to scan the interface, constraint features, etc. of the customized duct of a liquid rocket engine and obtain a point cloud, and the measured data of the customized duct interface and constraint features are extracted through the point cloud.

[0047] Design stage: Figure 2-7 As shown, the measured data of the customized catheter interface and constraint features are used to assemble the catheter sample and perform shape optimization to obtain the optimal tube shape of the customized catheter.

[0048] The measurement phase includes the following steps:

[0049] Use measurement equipment to measure the duct interfaces, constraint features, etc. on the engine and obtain point clouds.

[0050] Extract the center data and normal data of the catheter interface, the axis data and center data of the constraint features, etc.

[0051] The first interface coordinate of the catheter is (x S ,y S ,z S ), the direction vector is The second interface coordinates are (x E ,y E ,z E ), the direction vector is

[0052] The coordinates of the point (or sphere) feature on the engine are:

[0053]

[0054] Where P j represents the coordinates of the jth point feature, Represents the coordinate component of the jth constraint feature.

[0055] The cylindrical feature on the engine, the axis is extracted as:

[0056]

[0057] Where P lk is the vector representation of a point on the axis of the engine component, is the axis direction vector.

[0058] The design phase includes the following steps:

[0059] Step 1: Establish the assembly model of the duct sample and the interface. The duct sample is the initial form of the duct, which is generally the theoretical form during engine design. Figure 2 , Figure 3As shown, the model of the catheter sample and the models of the measured interface, constraint, etc. are respectively established through secondary development of CAD software; the catheter and the interface are assembled in the assembly so that the first and last straight line segments of the catheter pass through the interfaces on both sides respectively.

[0060] Step 2: Initialize the shape of the catheter sample. Figure 4 As shown, the key points at both ends of the catheter sample are driven to adjust the shapes of the straight segments at both ends of the catheter sample so that the straight segments at both ends of the catheter sample are collinear with the directions of the two interfaces respectively.

[0061] Step 3: Adjust the shape of the catheter and find the optimal solution. In the computer-aided design system, adjust the coordinates of the key points of the catheter, change the shape and posture of the catheter, make the designed catheter model as similar to the catheter sample as possible while satisfying the spatial constraints, and obtain the optimal tube shape by establishing a mathematical optimization model.

[0062] The mathematical optimization model for customized catheter tube shape design includes the following four parts:

[0063] (I) Design variables

[0064] Assuming that the catheter has n key points, there are n-1 straight line segments and n-2 bends. Set 3(n-4)+2 design variables x=(x1,x2,…,x 3(n-4)+2 ).

[0065] where x1, x2, ...x 3(n-4) Represents the component coordinates of key point 3 to key point n-2 in sequence x 3(n-4)+1 Represents the length of the first line segment of the catheter l1, x 3(n-4)+2 Represents the length of the last line segment l n-1 .

[0066] Since the interface position and direction vector are known, the first and last line segments of the catheter pass through the catheter interface point, and their directions are consistent with the interface direction. Point 2 and point (n-1) are connected by line segment lengths l1 and l n-1 The length of is determined, and the coordinates of key point 2 and key point (n-1) can be expressed by the coordinates of key point 1 and key point n respectively.

[0067]

[0068]

[0069] (II) Objective Function

[0070] The catheter sample model and the optimized model are translated and rotated to achieve optimal alignment, and then the mean of the sum of the position deviations of the corresponding points is calculated as the similarity index.

[0071] represents the initial coordinates of the key point i of the catheter sample model, P O It is the matrix representation of the key point set of the catheter sample model. The coordinates of the key point i of the catheter model after optimization, P G is the matrix representation of the key point set of the catheter optimized model. P O is the parameter of the catheter sample and is a known quantity.

[0072]

[0073] The optimal rigid transformation of the catheter sample and the optimization model is obtained by singular value decomposition (SVD).

[0074]

[0075] [U,S,V]=SVD(H)

[0076] R=VU T

[0077] T=-R*centroid O +centroid G

[0078] Among them centroid O and centroid G It is the point set P O and point set P G The mean center of ; H is the covariance matrix.

[0079] P ORT =R*P O +T

[0080] Where P ORT is the original point coordinate set P of the catheter O The coordinate set P after adjustment with the catheter shape G The aligned coordinate set. The similarity is defined as the point set P ORT With point set P G The mean of the distances between corresponding points:

[0081]

[0082] in It is the point set P ORT The i-th point in The coordinate value of .

[0083] The objective function is set as:

[0084] f(x)=φ(x)

[0085] (III) Constraints

[0086] Constraint 1: The length variation range of each catheter section should be within the control range.

[0087]

[0088] Its i represents the nominal length of the ith section of the conduit, Indicates the floating range of the i-th section of the catheter.

[0089] Constraint 2: Spacing requirements between the duct and other engine features.

[0090] Spacing requirements between the duct and point features on the engine:

[0091] d jmin ≤d j

[0092] where d j represents the distance between the catheter and the jth feature, d jmin Indicates the minimum required value of the distance value.

[0093] The vector distance formula from a point to a line is d j It can be expressed as:

[0094]

[0095] Where P j is the vector representation of the point feature on the engine, A j is the vector representation of any point on the catheter segment, is the direction vector of the jth segment of the catheter. × represents the cross product of the vectors, and || represents the modulus of the vector.

[0096] The distance constraint between the straight section of the duct and the axis of the engine upper component is:

[0097] d lkmin ≤d lk

[0098] Where d lk represents the distance between the conduit and the axis of the kth component, d ljmin Indicates the minimum required value of the spacing.

[0099] The distance between two straight lines can be calculated using the following formula:

[0100]

[0101] Where P lk and A lkare the vector representations of any point on the axis of the engine component and the corresponding straight line segment of the duct, respectively; |·| represents the modulus of the vector.

[0102] In the formula are the direction vectors of the two lines The cross product of:

[0103]

[0104] Constraint three: represents the spatial constraint range of each key point coordinate:

[0105]

[0106] where x kmin and x kmax The coordinate values ​​are x k The upper and lower limits of .

[0107] (IV) Mathematical Optimization Model

[0108] The customized catheter tube shape design model can be simplified into the following mathematical model:

[0109] Find x=(x1,x2,...,x 3(n-4)+2 )

[0110]

[0111] The above mathematical model is solved by genetic algorithm to obtain the optimal catheter model.

[0112] Step 4: Output the catheter CAD model. For the designed catheter model, the straight pipe segment angle including the pipe segment extension line is converted into a curved angle again, and a conventional catheter solid model is established.

[0113] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A customized catheter tube shape optimization design method, characterized in that: The following steps are involved: Measurement phase: Use measurement equipment to measure the interface of the customized duct of the liquid rocket engine, the position constraint characteristics of the duct and the pre-installed components on the engine, and extract the measured data of the interface at both ends of the duct and its position constraint characteristics; Design phase: Based on the measured data of the customized catheter interface and its position constraint features, the catheter sample is assembled and its shape is optimized to avoid interference with prefabricated components and obtain the optimal tube shape of the customized catheter.

2. A customized catheter tube shape optimization design method according to claim 1, characterized in that: The method of extracting measured data of the interfaces and position constraint features at both ends of the catheter comprises the following steps: Fit the center and normal data of the cross-section circle of the interface at both ends of the catheter; The prefabricated component is abstracted as a cylinder or a sphere, and the axis data of the cylinder and / or the center data of the sphere are extracted according to its position constraint features.

3. A customized catheter tube shape optimization design method according to claim 1, characterized in that: The design phase includes the following steps: Step 1: Establish model instances of the catheter sample, the measured interface, and the position constraint feature respectively; assemble the catheter and the interface so that the straight segments at the beginning and the end of the catheter pass through the interfaces on both sides respectively; the catheter sample is the initial theoretical form of the catheter design; Step 2: Initialize the shape of the catheter, drive the key points on the axis of the two ends of the catheter, and adjust the direction of the straight segments at both ends of the catheter so that the straight segments at both ends of the catheter are collinear with the normals of the two interfaces respectively; Step 3: Establish a mathematical optimization model. Under the condition of satisfying spatial constraints, adjust the coordinates of the key points of the catheter to change the shape and posture of the catheter, and find the optimal solution that makes the designed catheter model infinitely close to the shape of the catheter sample to obtain the optimal tube shape; Step 4: Output the optimal tube shape of the catheter, convert the straight tube segment angle including the tube segment extension line into a curved angle again, and establish a conventional solid model of the catheter.

4. A customized catheter tube shape optimization design method according to claim 4, characterized in that: The mathematical optimization model for customized catheter tube shape design includes the following steps: 1) Design variables The catheter shape is abstracted as a curve segment formed by connecting multiple straight line segments. If the catheter has n key points, there are n-1 straight line segments and n-2 bends. 2) Objective Function In order to avoid interference between the designed catheter and surrounding parts and make the designed catheter and the catheter sample as similar as possible, the catheter sample model and the optimized model are translated and rotated to align them optimally, and the mean of the position deviation of each corresponding point is taken as the similarity index and the objective function; 3) Constraints The length variation of each section of the catheter should be within the control range; The spacing requirements between the duct and other prefabricated component features on the engine; the spacing requirements include two types: the distance between the duct straight segment and the point constraint feature on the engine and the distance between the duct straight segment and the axis of the prefabricated component on the engine; The spatial constraint range of each key point coordinate.

5. A customized catheter tube shape optimization design method according to claim 4, characterized in that: The customized catheter tube shape design model is the following mathematical model: Find x=(x1,x2,...,x 3(n-4)+2 ) In the formula, x=(x1,x2,…,x 3(n-4)+2 ) is 3(n-4)+2 design variables, x 3(n-4)+2 Represents the length of the last line segment l n-1 ; The coordinates of the key point i of the catheter model after optimization, is the coordinate set P ORT The coordinates of the i-th point, P ORT is the original point coordinate set P of the catheter O The coordinate set P after adjustment with the catheter shape G Align the transformed coordinate set; where d j represents the distance between the catheter and the jth feature, d jmin Indicates the minimum required value of the distance value; d lk represents the distance between the conduit and the axis of the kth component, d ljmin Indicates the minimum required value of the spacing; x kmin and x kmax The coordinate values ​​are x k The upper and lower limits of .

6. A customized catheter tube shape optimization design method according to claim 5, characterized in that: The point set P after the alignment transformation ORT and the catheter original point coordinate set P O The transformation relationship is: P ORT =R*P O +T Where R represents the rotation matrix, T represents the translation matrix, and the original point coordinate set P of the catheter is O The coordinate set P after adjusting the catheter shape G Singular value decomposition (SVD) was performed to achieve the best alignment, thereby obtaining the best rigid transformation of the catheter sample and the optimized model.

7. A customized catheter tube shape optimization design method according to claim 5, characterized in that: The mathematical model is solved by a genetic algorithm to obtain an optimal catheter model.

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