A curved surface design method of a fuselage framework

Abstract

This invention belongs to the field of aircraft structural design technology, specifically relating to a surface design method for fuselage frames. The method first divides the cockpit frame components into four basic parts: left / right windshield frames, left / right door frames, and so on. The surface design of any one of these basic parts is implemented using the CATIA program, sequentially generating reference offset surfaces and boundaries; generating contour surfaces; and generating a digital model of the frame surface. The design method provided by this invention can be applied to the surface design of single parts with multiple overlapping surfaces, interfaces, and process separation surfaces, effectively improving design efficiency.

Description

Technical Field

[0001] This invention belongs to the field of aircraft structural design technology, specifically relating to a method for designing curved surfaces of an airframe. Background Technology

[0002] When designing the helicopter cockpit frame, considering that the frame is a rigid structure capable of transmitting loads, it not only connects the front skin, side skin, bottom skin, top skin, cockpit floor, and frame, but also houses the windshield, side windows, top window, doors, system cables, environmental control access, etc., involving complex assembly processes and numerous interface mounting surfaces, making the design relatively complex. However, by utilizing composite material design technology, a composite frame system with fewer parts and fewer assembly mounting surfaces can meet the design requirements. Therefore, based on the integrated approach, the cockpit frame components are designed as four basic parts: left / right windshield frames, left / right door frames, and four other basic parts. Although the number of parts is smaller, the surface design of each individual part is more complex. Summary of the Invention

[0003] The purpose of this invention is to propose a surface design method for the system design of the skeleton based on the curved shape, thereby forming a fixed design concept for the surface design steps of the cockpit skeleton.

[0004] The technical solution of this invention: a method for designing the curved surface of an airframe, wherein the design method first divides the cockpit frame parts into four basic parts: left / right windshield frames, left / right cabin door frames, etc.; the curved surface design of any one of the basic parts is implemented based on the CATIA program, including the following steps:

[0005] Step S1: Generate the reference offset surface and boundary lines;

[0006] Step S2: Generate the contour surface;

[0007] Step S3: Generate the skeleton surface digital model.

[0008] Furthermore, in step S1, the process of generating the reference offset surface and boundary lines is as follows: obtaining the nose, fuselage shape and cockpit interior shape; obtaining the fuselage shape skeleton boundary line and cockpit interior shape skeleton boundary line; obtaining the shape on the skeleton.

[0009] Furthermore, when obtaining the internal shape of the cockpit, based on the external dimensions of the skeleton cavity, the initial internal shape of the cockpit is generated by offsetting inward with the external surface of the nose and fuselage as the reference surface. The offset value is the maximum limiting size of the cavity.

[0010] Furthermore, during the inward offset process, the inward offset can be performed according to the maximum limit size of different skeleton cavities, and the connection can be trimmed and optimized to form the final optimized cabin interior shape.

[0011] Furthermore, when obtaining the boundary lines of the fuselage outer skeleton and the cabin inner skeleton, the method is to cut the fuselage outer skeleton boundary lines based on the skeleton layout and the dimensions of the ducts, using the fuselage nose and body shape as the reference surface. This generates the boundary lines of the fuselage outer skeleton, and the boundary lines of the windshield skeleton and the cabin door skeleton are then obtained. The boundary lines of the windshield skeleton and the cabin door skeleton are projected onto the cabin inner surface, and the projection dimensions are adjusted as needed to obtain the boundary lines of the windshield skeleton and the cabin door skeleton.

[0012] Furthermore, when acquiring the skeletal shape, the lower boundary of the upper viewing glass in the field of view is confirmed by offsetting the upper viewing glass boundary line of the field of view boundary area; from the skeletal boundary lines of the fuselage shape and the cockpit interior shape, the maximum limiting boundary lines of the skeletal shape of the fuselage shape and the cockpit interior shape near the lower boundary of the upper viewing glass are respectively confirmed; through analysis and comparison of the lower boundary of the upper viewing glass, the maximum limiting boundary lines of the skeletal shape of the fuselage shape and the cockpit interior shape are trimmed, connected and optimized to form two optimal skeletal shape boundary lines; finally, the two optimal skeletal shape boundary lines are filled with curved surfaces and trimmed to generate the skeletal shape.

[0013] Furthermore, in step S2, when generating the contour surface, the outer contour surface of the hatch frame, the outer contour surface of the windshield frame, the inner contour surface of the hatch frame, the inner contour surface of the windshield frame, the upper contour surface of the hatch frame, the ring contour surface of the hatch frame, the lower contour surface of the hatch frame, the upper contour surface of the windshield frame, the ring contour surface of the windshield frame, and the lower contour surface of the windshield frame are obtained respectively.

[0014] Furthermore, in step S3, the generation of the skeleton surface digital model includes obtaining the cabin door skeleton surface digital model and obtaining the windshield skeleton surface digital model.

[0015] Furthermore, the process of obtaining the hatch frame surface model involves combining the various contour surfaces of the hatch frame with an initial hatch frame surface model, and then performing detailed processing on the initial hatch frame surface model according to the interface to form the hatch frame surface model.

[0016] Furthermore, the process of obtaining the windshield frame surface model involves combining the various contour surfaces of the windshield frame with an initial surface model of the door frame; then, according to the interface, the initial surface model of the windshield frame is processed in detail to form the windshield frame surface model.

[0017] The beneficial effects of the present invention are: 1) The design method provided can be applied to the surface design of a single part with multiple overlapping surfaces, interfaces and process separation surfaces, which can effectively improve design efficiency;

[0018] 2) This invention belongs to the design concept of an integrated cockpit frame, which can simplify the design process;

[0019] 3) This invention fully utilizes the advantages of curved surface design in composite parts. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the overall shape and boundaries;

[0021] Figure 2 This is a schematic diagram of the skeleton line system layout;

[0022] Figure 3 This is a schematic diagram of the boundary between the inner and outer surfaces of the skeleton.

[0023] Figure 4 A schematic diagram of the outer contour of the hatch frame;

[0024] Figure 5 A schematic diagram illustrating the process of generating the outline of the cockpit door frame.

[0025] Figure 6 This is a schematic diagram of the generated hatch frame surface. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The following describes the invention in detail using the curved surface design of the hatch frame as an example. See appendix. Figure 1-6 The cabin door frame curved surface design method is a CATIA program-based approach to designing the cabin frame shape based on curved surfaces. The steps to solve the above problem are as follows:

[0028] First, generate the reference offset surface and boundary.

[0029] 1. Obtain the nose and fuselage outline and cockpit interior shape: Obtain the following inputs from the overall structure: nose and fuselage outline, field of view boundary area, frame 1 reference plane (main load-bearing frame behind the nose), and cockpit floor reference plane. Based on preliminary strength assessments and the condition of the field of view boundary area, confirm the arrangement and structural form of the frame (including the cross-section, thickness, and external dimensions of the ducts). Based on the external dimensions of the frame ducts, using the nose and fuselage outline as the reference surface, offset inwards to generate the preliminary cockpit interior shape. The offset value is the maximum limiting dimension of the ducts. The cockpit interior shape can be further offset inwards according to different maximum limiting dimensions of the frame ducts, and then trimmed and optimized to form the final optimized cockpit interior shape.

[0030] 2. Obtain the boundary lines of the fuselage outer skeleton and the cabin interior skeleton: Based on the skeleton layout and the dimensions of the ducts, using the fuselage nose as the reference surface, trim the skeleton to generate the boundary lines of the fuselage outer skeleton, and obtain the boundary lines of the windshield skeleton and the cabin door skeleton. Project the boundary lines of the windshield skeleton and the cabin door skeleton onto the cabin interior surface, and adjust the projection dimensions as needed to obtain the boundary lines of the windshield skeleton and the cabin door skeleton.

[0031] 3. Obtaining the Skeleton Upper Shape: By offsetting the upper glass boundary line of the field of view boundary area, confirm the lower boundary (curve or surface) of the upper glass in the field of view boundary area; from the skeleton boundary lines of the fuselage shape and cockpit interior shape, respectively confirm the maximum limiting boundary lines of the skeleton upper shape of the fuselage shape and cockpit interior shape near the lower boundary of the upper glass; through analysis and comparison of the lower boundary of the upper glass, trim, connect and optimize the maximum limiting boundary lines of the skeleton upper shape of the fuselage shape and cockpit interior shape to form two optimal skeleton upper shape boundary lines (one on the fuselage shape and the other on the cockpit interior shape). The lines should have a smooth transition, and the line ends should extend to the first frame reference plane (in the direction of flight). Perform surface filling processing on the two optimal skeleton upper shape boundary lines and trim them to generate the skeleton upper shape.

[0032] Second, generate the contour surface.

[0033] 1. Obtaining the Outer Contour Surface of the Door Frame: Based on the boundary lines of the fuselage frame related to the door section, the initial outer contour surface of the door frame is generated through optimization processes such as offsetting, rounding, transitioning, connecting, and trimming on the fuselage shape. According to the overlaps of the roof, upper viewing glass, side skin, and panels, the corresponding overlap areas are obtained. The corresponding curved surfaces are then subjected to appropriate inward offset processing based on the overlap depth and thickness to form overlap surfaces. The outer contour surface and multiple overlap surfaces are bridged and combined to generate a smoothly transitioned curved surface.

[0034] 2. Obtaining the outer contour surface of the windshield frame: Based on the boundary lines of the fuselage frame related to the windshield, the initial outer contour surface of the windshield frame is generated through optimization processes such as offsetting, rounding, transitioning, connecting, and trimming on the fuselage shape. According to the overlaps of the roof, upper viewing glass, nose skin, door frame, and panels, the corresponding overlap areas are obtained. The corresponding curved surfaces are then subjected to appropriate inward offset processing based on the overlap depth and thickness to form overlap surfaces. The outer contour surface and multiple overlap surfaces are bridged and combined to generate a smoothly transitioned curved surface.

[0035] 3. Obtain the inner contour surface of the cabin door frame: Based on the boundary line of the cabin interior frame related to the cabin door, the inner shape of the cabin is generated through optimization processes such as offsetting, rounding, transitioning, connecting and trimming.

[0036] 4. Obtain the inner contour surface of the windshield frame: Based on the boundary line of the cabin inner shape frame related to the windshield, the inner shape of the cabin is generated through optimization processes such as offset, rounding, transition, connection and trimming.

[0037] 5. Obtain the outline surface of the cabin frame: Generate a curved surface by bridging and trimming the upper boundary line between the outer shape of the frame and the inner shape of the cabin.

[0038] 6. Obtain the hatch frame ring contour surface: Extract the inner edge curves of the inner contour surface and the outer contour surface of the hatch frame respectively, and generate a surface by bridging the two closed curves.

[0039] 7. Obtain the lower skin contour surface of the hatch frame: Extract the lower edge curves of the inner contour surface and the outer contour surface of the hatch frame respectively, and generate a single surface from the two curves through bridging processing.

[0040] 8. Obtain the contour surface of the windshield frame: Generate a curved surface by bridging and trimming the upper boundary line between the outer shape of the frame and the inner shape of the cabin.

[0041] 9. Obtain the windshield frame ring contour surface: Extract the inner edge curves of the inner contour surface and the outer contour surface of the windshield frame respectively, and generate a single surface by bridging the two closed curves.

[0042] 10. Obtain the lower contour surface of the windshield frame: Extract the lower edge curves of the inner contour surface and the outer contour surface of the windshield frame respectively, and generate a single surface from the two curves through bridging processing.

[0043] Third, generate the skeleton surface digital model.

[0044] 1. Obtain the hatch frame surface model: Combine the various contour surfaces of the hatch frame into an initial hatch frame surface model. Perform detailed processing on the initial hatch frame surface model according to the interface to form the hatch frame surface model.

[0045] 2. Obtain the windshield frame surface model: Combine the various contour surfaces of the windshield frame with an initial surface model of the door frame. Perform detailed processing on the initial surface model of the windshield frame according to the interface to form the windshield frame surface model.

[0046] See appendix Figure 5 Taking the generation process of the cabin door frame outline as an example, the specific generation process is as follows:

[0047] The outer contour surface Q1 of the hatch frame: Based on the boundary lines of the fuselage frame related to the hatch section, the initial outer contour surface of the hatch frame is generated through optimization processes such as offsetting, rounding, transitioning, connecting, and trimming on the fuselage shape. According to the overlaps of the roof, upper viewing glass, side skin, and panels, the corresponding overlap areas are obtained, and their corresponding curved surfaces are subjected to appropriate inward offset processing based on the overlap depth and thickness to form overlap surfaces. The outer contour surface and multiple overlap surfaces are bridged and combined to generate a smoothly transitioned curved surface.

[0048] The inner contour surface Q2 of the cabin door frame: Based on the boundary line of the cabin interior frame related to the cabin door, a smooth curved surface is generated on the cabin interior shape through optimization processes such as offset, rounding, transition, connection and trimming.

[0049] Door frame ring contour surface Q3: Extract the inner edge curves L1 and L2 of the outer contour surface Q1 and the inner contour surface Q2 of the door frame respectively, and generate a surface by bridging the two closed curves.

[0050] Lower skin contour surface Q4 of the hatch frame: Extract the lower edge curves L3 and L4 of the outer contour surface Q1 and the inner contour surface Q2 of the hatch frame respectively, and close the two curves to generate a surface through bridging processing.

[0051] The upper skin contour surface Q5 of the hatch frame is a curved surface generated by bridging, trimming and closing the upper boundary line between the outer shape of the frame and the inner shape of the cabin, based on the outer contour surface Q1 and the inner contour surface Q2 of the hatch frame.

[0052] Finally, the contour surfaces Q1, Q2, Q3, Q4, and Q5 are merged to form the complete cockpit door frame contour surface. After detailed processing such as interface addition and smooth transition, this contour surface finally becomes the digital model of the cockpit door frame surface.

[0053] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for designing the curved surface of a fuselage frame, characterized in that, The design method first divides the cockpit frame parts into four basic parts: left and right windshield frames and left and right cabin door frames. The surface design of any basic part is implemented using the CATIA program, including the following steps: Step S1: Generate the reference offset surface and boundary lines; Step S2: Generate the contour surface; Step S3: Generate the skeleton surface digital model; In step S1, the process of generating the reference offset surface and boundary lines is as follows: obtain the nose, fuselage shape and cockpit interior shape; obtain the fuselage shape skeleton boundary line and cockpit interior shape skeleton boundary line; obtain the shape on the skeleton. When obtaining the internal shape of the cockpit, the initial internal shape of the cockpit is generated by offsetting inward based on the external dimensions of the skeleton cavity and the external surface of the nose and fuselage, with the offset value being the maximum limit size of the cavity. When obtaining the boundary lines of the fuselage outer skeleton and the cabin inner skeleton, the method is to cut the fuselage outer skeleton based on the skeleton layout and the dimensions of the cavity, using the fuselage nose as the reference surface, to generate the boundary lines of the fuselage outer skeleton, and obtain the boundary lines of the windshield skeleton and the cabin door skeleton. The boundary lines of the windshield skeleton and the cabin door skeleton are then projected onto the cabin inner surface, and the position and size of the projection are adjusted as needed to obtain the boundary lines of the windshield skeleton and the cabin door skeleton. When obtaining the skeletal shape, the lower boundary of the upper viewing glass in the field of view is identified by offsetting the upper viewing glass boundary line of the field of view boundary area. From the skeletal boundary lines of the fuselage shape and the cockpit interior shape, the maximum limiting boundary lines of the skeletal shape of the fuselage shape and the cockpit interior shape near the lower boundary of the upper viewing glass are identified respectively. Through analysis and comparison of the lower boundary of the upper viewing glass, the maximum limiting boundary lines of the skeletal shape of the fuselage shape and the cockpit interior shape are trimmed, connected and optimized to form two optimal skeletal shape boundary lines. Finally, the two optimal skeletal shape boundary lines are filled with curved surfaces and trimmed to generate the skeletal shape.

2. The method for designing the curved surface of the fuselage frame as described in claim 1, characterized in that, During the inward offset process, the inward offset is performed according to the maximum limit size of different skeleton cavities, and the connection is trimmed and optimized to form the final optimized cabin interior shape.

3. The method for designing the curved surface of the fuselage frame as described in claim 1, characterized in that, In step S2, when generating the contour surface, the outer contour surface of the hatch frame, the outer contour surface of the windshield frame, the inner contour surface of the hatch frame, the inner contour surface of the windshield frame, the upper contour surface of the hatch frame, the ring contour surface of the hatch frame, the lower contour surface of the hatch frame, the upper contour surface of the windshield frame, the ring contour surface of the windshield frame, and the lower contour surface of the windshield frame are obtained respectively.

4. The method for designing the curved surface of the fuselage frame as described in claim 1, characterized in that, In step S3, the generation of the skeleton surface digital model includes obtaining the cabin door skeleton surface digital model and obtaining the windshield skeleton surface digital model.

5. The method for designing the curved surface of the fuselage frame as described in claim 4, characterized in that, The process of obtaining the hatch frame surface model involves combining the various contour surfaces of the hatch frame with an initial hatch frame surface model, and then performing detailed processing on the initial hatch frame surface model according to the interface to form the hatch frame surface model.

6. The method for designing the curved surface of the fuselage frame as described in claim 4, characterized in that, The process of obtaining the windshield frame surface model involves combining the various contour surfaces of the windshield frame into an initial windshield frame surface model; then, according to the interface, the initial windshield frame surface model is processed in detail to form the windshield frame surface model.

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