A system for assisting in the design of a tensile-torsional strip

Abstract

The application belongs to the technical field of helicopter rotor design, and discloses a tensile-torsional strip auxiliary design system, which comprises a guidance module, a calculation module and an optimization module, and the guidance module is internally provided with design documents of typical tensile-torsional strips; according to the input of a user, the guidance module pushes the corresponding design documents of typical tensile-torsional strips to the user; the calculation module is internally provided with a design parameter input port of the tensile-torsional strip, and after the user inputs the corresponding design parameters into the input port, the calculation module automatically calculates and outputs the torsional stiffness, maximum stress and safe life of the tensile-torsional strip; the optimization module calculates the tensile-torsional strip according to the calculation module, adopts an optimization algorithm to optimize the scheme according to the correlation between various input and output parameters, and pushes the scheme to the user. The application can obtain the parameters and structural scheme of the tensile-torsional strip, plays a role of replacing a tutor, sets a separate optimization target according to the calculation result, and automatically generates a tensile-torsional strip scheme with material information and specific structural parameter details.

Description

Technical Field

[0001] This invention belongs to the field of helicopter rotor design technology, and relates to a design system for helicopter torsion bars, specifically an auxiliary design system for torsion bars. Background Technology

[0002] In helicopter rotors, there is a type of structural component that requires deformation to achieve blade torsion. These components typically exhibit high flapping and yaw stiffness but low torsional stiffness, requiring torsional deformation under high tensile forces. The loading pattern for these structures is generally one end fixed and constrained, while the other end is torsion-capable, exhibiting constrained torsional deformation at both connection points. Examples include the torsional deformation section of a flexible beam in a bearingless rotor and tension-torsion strips replacing pitch hinges. These components require static and dynamic torsional deformation under large centrifugal forces. Currently, in the domestic helicopter engineering industry, the treatment of torsional problems in beams typically employs free torsion calculations from materials mechanics to determine the torsional stiffness, shear stress, and normal stress generated by torque. This approach is acceptable for components with high torsional stiffness, but for components with very low torsional stiffness, especially those with a large ratio of flapping and yaw stiffness to torsional stiffness, this calculation becomes inaccurate, potentially leading to design failures.

[0003] In the 2020s, the development of domestic helicopter models placed more stringent demands on the design of tension-torsion strips. Lighter weight requirements necessitated composite material structures for the strips. Large centrifugal forces, high-frequency, high-amplitude torsional motion, and the unidirectional reinforcing characteristics of composite materials made tension-torsion coupling a serious constraint on the lifespan of the strips. Referring to foreign methods using finite element analysis (FEM), selecting the optimal solution from different designs based on FEM analysis results, this method is time-consuming for composite parts. It requires a significant amount of time to find the key stress parameters for optimization, and there is also the risk of design failure due to inappropriate constraint settings in the FEM calculations leading to incorrect results. There is an urgent engineering need for technical analysis software that, starting from the fundamental principles, can qualitatively and quantitatively calculate the coupling between tension and torsion. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes an auxiliary design system for tension-torsion bars, which has been applied to a domestic helicopter model. This system solves the problems of tension-torsion bar calculation and design guidance. The system concept of this invention can be extended to all structural components that undergo torsional deformation under high tension and can replace some thrust bearings.

[0005] The technical solution of the present invention: An auxiliary design system for tension / torsion bars includes a guidance module, a calculation module, and an optimization module. The guidance module contains design documents for typical tension / torsion bars. Based on user input, the guidance module pushes the corresponding typical tension / torsion bar design documents to the user. The calculation module has input ports for design parameters of the tension / torsion bar. After the user inputs the corresponding design parameters, the calculation module automatically calculates and outputs the torsional stiffness, maximum stress, and safe life of the tension / torsion bar. The optimization module calculates the tension / torsion bar based on the calculation module, and uses an optimization algorithm to calculate an optimized solution based on the correlation between various input and output parameters, and then pushes it to the user.

[0006] Furthermore, it also includes a computer, and the guidance module, calculation module, and optimization module are all tension bar design software modules, which are installed in the computer's memory.

[0007] Furthermore, in the guidance module, users can select two operating conditions: the first is non-cyclic control input, and the second is cyclic control input. When the first operating condition is selected, the guidance module pushes typical pull-torsion bar design documents for the tail rotor and thrust rotor. When the second operating condition is selected, the guidance module pushes typical pull-torsion bar design documents for the main rotor. The typical pull-torsion bar design documents include the shape of the typical pull-torsion bar, the detailed structure of the typical torsion section and the connecting section, and an interpretation of the design points for material selection.

[0008] Furthermore, in the guidance module, the user inputs a fixed tensile force, and the guidance module pushes typical tension bar design documents that conform to the range of that fixed tensile force.

[0009] Furthermore, in the calculation module, the user input parameters include angular displacement spectrum, tensile force, tension bar shape, and material parameters used. The calculation module displays simplified formulas in the calculation results for the parameters being calculated, and shows which input parameters control the parameters in the calculation results.

[0010] Furthermore, the calculation module takes the number of input parameters as follows: first, it calculates the typical torsion segment, then it calculates multiple connected components of the typical torsion segment, and then it calculates the results of each connected component separately and then superimposes them to realize the structural calculation of the entire tension-torsion bar. Finally, it calculates the stress of the connection part based on the overall torsional stiffness of the tension-torsion bar and outputs the stress results.

[0011] Furthermore, the specific calculation modules and formulas are as follows:

[0012] in,

[0013] Furthermore, the optimization module includes the following steps to obtain the optimization solution: Step 1: Obtain the transfer relationship between input parameters and design results; Step two: Linearize the real control system using transitive relational expressions; Step 3: Based on the measurement and system model, perform data correction using the Kalman filter model on the linearized transfer relationship; Step four: Solve for the minimum performance parameters to obtain the optimal control input.

[0014] The beneficial effects of this invention are: 1. This invention proposes a software solution for designing tension / torsion bars. This software can obtain the parameters and structural schemes of tension / torsion bars. It can replace tutors and partially replace designers, categorizing structural component designs into relevant fields based on working conditions, allowing users to immediately obtain design explanations and case studies of similar domestic and international structures.

[0015] 2. The method of this invention can be used as a calculator to perform calculations on the input parameters. Individual optimization targets can be set based on the calculation results, such as reducing torsional stiffness by 50%, and the software will generate multiple modification suggestions. Simultaneously, the software can automatically generate tension-torsion bar design schemes, which can automatically generate a tension-torsion bar scheme with material information and specific structural parameters based on operating conditions, size limitations, elongation limitations, overall torsional stiffness limitations, and lifespan requirements.

[0016] 3. It can be directly applied to the design of all tension bars and flexible beam torsional deformation sections in all helicopter rotor systems.

[0017] 4. At the same time, it can also be further promoted to the market. Companies with corresponding advantages in the market can use this software to develop bearing structures with tension bars based on similar application scenarios, replacing existing thrust bearings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the segmented tension bar; Figure 2 This is a top view of the torsion center of the tension bar; Among them, 1—typical twisting segment, 2—connecting segment. Detailed Implementation

[0019] This section describes embodiments of the present invention, used to explain and illustrate the technical solutions of the present invention. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating directions or positional relationships, are given in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or device referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include more than one of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integrated connections; they can refer to mechanical connections or point connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] This invention proposes a software solution for designing tension-to-torsion strips. This software can obtain the parameters and structural schemes of tension-to-torsion strips. It can replace tutors and partially replace designers, categorizing structural component designs into relevant areas based on operating conditions, and providing users with immediate access to design explanations and case studies of similar domestic and international structures. The software can also function as a calculator, performing calculations on the input parameters. Individual optimization targets can be set for the calculation results; for example, if a 50% reduction in torsional stiffness is required, the software will generate multiple modification suggestions. Simultaneously, the software can automatically generate tension-to-torsion strip design schemes, automatically generating a scheme with material information and detailed structural parameters based on operating conditions, size limitations, elongation limitations, overall torsional stiffness limitations, and lifespan requirements.

[0023] The software for designing tension bars is divided into three modules: guidance, calculation, and optimization.

[0024] 1. The first module of the software identifies the user's design requirements based on the input working conditions, including two working conditions: Operating condition 1. Constant tension, no periodic control input; Operating condition 2. Constant tension, with periodic control input; Selecting Operation Condition 1 will take you to the design guidance interface for the tail rotor and thrust rotor torsion bar. This interface includes an explanation of the shape of existing tail rotor torsion bars from both domestic and international sources, the detailed structure of typical torsion section 2 and connecting section 1, and key design considerations for material selection. Selecting Operation Condition 2 will take you to the rotor torsion bar design guidance interface. This interface includes an explanation of the shape of existing main rotor torsion bars from both domestic and international sources, the detailed structure of typical torsion section 2 and connecting section 1, and key design considerations for material selection. The software also includes design examples of similar torsion bar structures. This part of the software was developed specifically to implement the design guidance function, helping users design new torsion bar solutions from principles to examples.

[0025] 2. The second module of the software is the calculation section, which calculates torsional stiffness, maximum stress, and safe life based on the input parameters. Input parameters include angular displacement spectrum, tensile force, tension bar shape, and material parameters. Parameters related to the shape are illustrated with diagrams, such as... Figure 2 As shown, the calculated parameters, with simplified formulas near the calculation results, indicate which input parameters control that parameter. This section serves both calculation and design guidance functions.

[0026] The software first calculates the stress on typical torsional segment 2. The calculation method for multiple connected components in typical torsional segment 2 is achieved by calculating the results of each connected component separately and then superimposing them. Then, based on the overall torsional stiffness, the stress at the connection points is calculated.

[0027] The load-bearing characteristic of a tension-torsion strip is that its torsional load is generated by its own torsional deformation, the amount of deformation being the angle of the pitch change, given a fixed angle requirement. The load of the tension-torsion strip is proportional to its stiffness, so the key to tension-torsion strip design is stiffness design. Not all parts of the tension-torsion strip have their centroids passing through the torsion center. When the centroid deviates from the torsion center, this part will bend during torsion. The torsion of the tension-torsion strip also needs to overcome the torque generated by this bending. The introduction of tension force changes the bending stiffness of various parts of the tension-torsion strip, thus affecting the torsional stiffness and stress distribution. These three parts of torsional stiffness constitute the total torsional stiffness of the tension-torsion strip. In the calculation of each simply connected domain, based on the characteristics of the torsional structure under tension, the torsional stiffness is divided into three parts: free torsion, bending-constrained torsion, and additional torsional stiffness caused by tension. The software visually presents the influence of each part on the stress in different areas of the tension-torsion strip, and what structural parameters cause these influences.

[0028]

[0029] in,

[0030] 3. The third module is for design optimization schemes given for single and multiple objectives.

[0031] By establishing the relationships between the various input and output parameters in the second module, an optimization algorithm is used to obtain an optimal solution. For example, an adaptive optimization algorithm.

[0032] First, you need to obtain the input parameters. With design results The transitive relationship between inputs and design results can be described as follows:

[0033] The above process is a local model, that is, a local linearization process. Although the response of the real system to various parameters is nonlinear, the increments are not too large, so the above expression can be used to linearize the real control system. You can specify it yourself, for example F0 is the design result vector under zero input. It is an adjustable design vector. Then T can be represented as: The typical input parameter is... The relationship between F and the input parameters.

[0034] The T-matrix is ​​identified through input. △F is obtained by △F / △δ.

[0035] To make it easier to understand, the expression above will be transformed as follows: To make it easier to understand, the expression above will be transformed as follows:

[0036] At any iteration step n, it can be expressed as:

[0037] Here It is a measurement vector. It is the state vector that needs to be calculated. It is a measurement matrix. The mean of the simulated measurement process is zero, and the covariance is... White noise.

[0038]

[0039] here The simulation is of process noise, with a mean of zero and a covariance of... Based on the measurement and system model, the data correction process of the Kalman filter model can be described as follows: Kalman gain matrix:

[0040] Update of the covariance of the error:

[0041] Status correction:

[0042] Note that the gain vector is the same for all rows, so the unknown parameters... It can be identified in one step:

[0043] The process of finding the optimal control input is essentially an optimization problem, specifically minimizing the performance parameter J. In this paper, the performance parameter represents:

[0044]

[0045]

[0046] here To simplify the notation, the subscript n representing the iteration number is omitted here. , and These represent the weighted matrices for the output response, control input amplitude, and control state, respectively. They are all diagonal matrices, chosen to maintain consistency with the uncontrolled output portion. Some diagonal elements can be set to zero.

[0047] The optimal control input is to minimize the objective function J, that is, to find time :

[0048] This is how the optimal control input is obtained.

[0049] 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 system for assisting in the design of a tensile-torsional strip, characterized in that It includes a guidance module, a calculation module, and an optimization module. The guidance module contains design documents for typical tension and torsion bars. Based on the user's input, the guidance module pushes the corresponding typical tension and torsion bar design documents to the user. The calculation module has a design parameter input port for the tension bar. After the user inputs the corresponding design parameters into the input port, the calculation module automatically calculates and outputs the torsional stiffness, maximum stress and safe life of the tension bar. The optimization module calculates the tension bar based on the calculation module, and uses an optimization algorithm to calculate the optimization scheme based on the correlation between various input and output parameters, and pushes it to the user; In the calculation module, the user input parameters include angular displacement spectrum, tensile force, tension bar shape and material parameters. The calculation module displays simplified formulas in the calculation results for the calculated parameters and shows which input parameters control the parameters of the calculation results. The calculation module takes the number of input parameters as its core. First, it calculates the typical torsion segment, then it calculates multiple connected domains of the typical torsion segment. Then, it calculates the results of each connected domain separately and then superimposes them to realize the structural calculation of the entire tension-torsion bar. Finally, it calculates the stress of the connection part based on the overall torsional stiffness of the tension-torsion bar and outputs the stress results. The specific calculation modules and formulas are as follows: Sectional free torsional stiffness: ； Additional cross-sectional torsional stiffness under tension: ； Elongation under tension: ； Distribution of torsion angles with tension centroid deviating from torsion center and constrained at both ends: ； in, ; The distribution of torsion angles at both ends of the centroid without tension and constrained by the torsion center is obtained by setting Fc=0. ... get; Shear stress calculation: ； ； in ; Normal stress calculation: ； in ; Overall torsional stiffness: ； Overall torsional stiffness of N connected domains: ； Equivalent dynamic load: ； Lifespan of the torsion bar: ； in, ; In the above formula, It is the total free torsional stiffness of the cross section. It is tension. It is the distance from the connecting end face in the direction of the tensile force. It is the chordal distance from the direction of the tension to the center of rotation. It is the distance in the direction of the pulling force from the center of rotation in the vertical direction. It is the chordal distance from the centroid of the connected domain to the center of rotation. It is the distance in the height direction from the centroid of the connected domain to the center of rotation. It refers to the overall torsional stiffness of the tension bar. It is the sum of the areas of all connected regions in a typical twisted section profile. It is the torque applied to the rod. The angle of twist of the rod is related to The second derivative, It is the normal stress in the direction of tension. It is the centrifugal force that adds torsional stiffness in the cross section. It is the moment of inertia of the cross-section about the y-axis. It is the distribution of the twist angle of the rod. is the moment of inertia of the cross-section about the z-axis, and 'a' is the thickness of the rectangular cross-section. This represents the warping of the cross-section when the rectangular bar is torsioned, where h is the length of the rectangular cross-section, K is the moment decay frequency on the beam, and E is the Young's modulus of the material used in the rectangular cross-section structure. Let L represent the overall torsional stiffness of the connected domain, L be the typical length of the torsional segment of the tension bar, and G be the shear modulus of the material used in the rectangular cross-section structure. These are the shape parameters of the composite material SN. Let i be the alternating load for the i-th operating condition. For equivalent dynamic load, To allow the number of loops, Elongation under tension Let n be the lifespan of the torsion bar, and n be the number of blocks. This represents the fatigue limit of the material.

2. The auxiliary design system for a tension / torsion bar according to claim 1, characterized in that, It also includes a computer, and the guidance module, calculation module and optimization module are all tension bar design software modules, which are installed in the computer's memory.

3. The auxiliary design system for a tension / torsion bar according to claim 1, characterized in that, In the guidance module, users can select two operating conditions: the first is non-cyclic control input, and the second is cyclic control input. When the first operating condition is selected, the guidance module pushes typical pull-torsion bar design documents for the tail rotor and thrust rotor. When the second operating condition is selected, the guidance module pushes typical pull-torsion bar design documents for the main rotor. The typical pull-torsion bar design documents include the shape of the typical pull-torsion bar, the detailed structure of the typical torsion section and the connecting section, and an interpretation of the design points for material selection.

4. The auxiliary design system for a tension / torsion bar according to claim 1, characterized in that, In the guidance module, the user inputs a fixed tensile force, and the guidance module pushes typical tension bar design documents that conform to the range of the fixed tensile force.

5. The auxiliary design system for a tension / torsion bar according to claim 1, characterized in that, The optimization module includes the following steps to obtain the optimization solution: Step 1: Obtain the transfer relationship between input parameters and design results; Step two: Linearize the real control system using transitive relational expressions; Step 3: Based on the measurement and system model, perform data correction using the Kalman filter model on the linearized transfer relationship; Step four: Solve for the minimum performance parameters to obtain the optimal control input.

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