Multi-objective optimization design method for light truck frame

Abstract

The invention discloses a multi-objective optimization design method of a light truck frame, and relates to the technical field of computer simulation design of the light truck frame, and the method comprises the steps: building a finite element model of the light truck frame; determining the static and dynamic working conditions of the light truck frame and the weight coefficient of each sub-working condition; performing multi-working-condition multi-target topological optimization on the finite element model according to the static and dynamic working conditions of the light truck frame and the weight coefficient of each sub-working condition; performing main effect analysis on the light truck frame; carrying out multi-target size optimization calculation on the frame of the light truck; and comparing the performances of the light truck frame before and after optimization. The high-strength lightweight design of the light truck frame is completed through multi-working-condition multi-target topological optimization and multi-target size optimization, and the static and dynamic performance of the frame is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of computer simulation design of light truck frames, and particularly to a multi-objective optimization design method for light truck frames. Background Art

[0002] When optimizing and analyzing a light truck frame, generally, corresponding performance calculations are carried out according to each single discipline, and then optimization is carried out according to each target value. Each performance calculation and optimization direction is independent and incomplete, which is one-sided. It is impossible to comprehensively optimize the optimal performance, and thus it is impossible to obtain the optimal cross-section thickness, minimum frame mass, minimum turning flexibility, and maximum first-order dynamic frequency based on all performances. Summary of the Invention

[0003] The present application provides a multi-objective optimization design method for a light truck frame to solve at least one technical problem existing in the related art.

[0004] According to one aspect of an embodiment of the present application, a multi-objective optimization design method for a light truck frame is provided, including: establishing a finite element model of the light truck frame; determining the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub-working condition; performing multi-condition multi-objective topology optimization on the finite element model according to the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub-working condition; performing a main effect analysis on the light truck frame; performing a multi-objective size optimization calculation on the light truck frame; and comparing the performances of the light truck frame before and after optimization.

[0005] As an optional implementation manner, the establishment of the finite element model of the light truck frame includes: determining the geometric digital models of the longitudinal beam, cross beam, and connecting plate of the light truck frame, the brackets directly connected to the frame, the suspension system, the axle, and the tire; performing pre-processing on the geometric digital models and converting the geometric digital models into discrete finite element models.

[0006] As an optional implementation manner, the determination of the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub-working condition includes: determining the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub-working condition; calculating the weight coefficients of each sub-working condition according to the orthogonal analysis method to obtain the reference ratio of the importance degree between each sub-working condition.

[0007] As an alternative implementation, the determination of the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition further includes: pairwise matching and comparison of the sub - working conditions; judging whether the matrix eigenvalue and eigenvector are consistent in evaluating the importance degree of each working condition; if the matrix eigenvalue and the eigenvector are consistent in evaluating the importance degree of each working condition, determining the maximum matrix eigenvalue and the corresponding eigenvector, and performing normalization processing on the eigenvector to obtain the weight coefficients of each static and dynamic sub - working condition in the multi - working - condition and multi - objective topology optimization of the light truck frame; selecting bending flexibility, torsional flexibility, turning flexibility, braking flexibility, and the first 5 - order dynamic frequencies of the frame to perform multi - working - condition and multi - objective topology optimization on the light truck frame to obtain a judgment matrix of the importance degree of static and dynamic sub - working conditions; determining the maximum eigenvalue and the corresponding eigenvector of the judgment matrix of the importance degree of static and dynamic sub - working conditions, and determining the final static and dynamic working conditions of the frame and the final weight coefficients of each sub - working condition according to the eigenvector.

[0008] As an alternative implementation, the multi - working - condition and multi - objective topology optimization of the finite - element model according to the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition includes: establishing a multi - working - condition and multi - objective topology optimization design space; taking the relative density of the design - area units of the light truck frame as the design variable, the volume fraction of the design area as the constraint, and the minimum static flexibility and the maximum low - order dynamic frequency of the frame under multi - working conditions as the objectives, and defining through the variable - density method combined with the compromise programming method, the average - frequency formula, and the efficacy - coefficient method to obtain the multi - working - condition and multi - objective topology - optimization mathematical model of the light truck frame; determining the maximum - flexibility function and the minimum - flexibility function of the light truck frame under the static sub - working conditions by single - working - condition optimization, and obtaining the maximum and minimum frequency functions of the low - order frequency band under the dynamic sub - working conditions; defining the multi - working - condition and multi - objective topology - optimization function of the frame through the dequtions section in OptiStruct in combination with each response.

[0009] As an alternative implementation, the main - effect analysis of the light truck frame includes: grouping the variables of the frame cross - members according to the structural symmetry of the light truck frame and the cross - section thickness of the cross - members; taking the mass of the light truck frame, turning flexibility, and the first - order dynamic frequency as the design responses, and performing the main - effect analysis of the mass, turning flexibility, and the first - order dynamic frequency on the frame design - variable group through the design of experiments (DOE) in HyperStudy; judging whether the contribution degrees of multiple grouped design variables to the turning flexibility and the first - order dynamic frequency of the frame are higher than a preset value; if there is a group among the multiple grouped design variables whose contribution degrees to the turning flexibility and the first - order dynamic frequency of the frame are higher than the preset value, and the grouped design variables with contribution degrees higher than the preset value are negatively correlated with the turning flexibility, or positively correlated with the first - order dynamic frequency, then performing multi - objective size optimization on the grouped design variables with contribution degrees not higher than the preset value.

[0010] As an alternative implementation, the multi-objective dimensional optimization calculation of the light truck frame includes: setting the cross-section thickness of the design variables grouped with a contribution degree not higher than the preset value as the optimization variables, taking the minimum frame mass, the minimum turning flexibility, and the maximum first-order dynamic frequency as the objectives, and performing multi-objective dimensional optimization on the frame through the global response surface method (GRSM); establishing an optimization mathematical model; obtaining the values of the frame cross-section thickness before optimization, after optimization, and after rounding, substituting the rounded value of the compromise optimal solution into the optimized frame, and analyzing and comparing the static and dynamic performances of the frame before and after optimization.

[0011] As an alternative implementation, the comparison of the performances of the light truck frame before and after optimization includes: performing static analysis, modal analysis, etc. on the original light truck frame and the frame after multi-condition multi-objective topology optimization and multi-objective dimensional optimization to obtain the frame constraints.

[0012] As an alternative implementation, the comparison of the performances of the light truck frame before and after optimization further includes: when calculating the bending flexibility, the xz degrees of freedom of the left front wheel of the whole vehicle are constrained, the xyz degrees of freedom of the right front wheel are constrained, the z-direction degree of freedom of the rear wheels is constrained, the constraint position is at the tire contact point, and a vertical downward dynamic load coefficient of 3.5g is applied to the whole frame; when calculating the turning flexibility, the xz degrees of freedom of the left front wheel of the whole vehicle are constrained, the z-direction degree of freedom of the right front wheel is constrained, the z-direction degree of freedom of the rear wheels is constrained, the end of the frame grounding spring connected to the ground is constrained by 2, and a vertical self-weight acceleration of -1g and a lateral dynamic load coefficient of 0.5g are applied to the whole frame; when calculating the torsional flexibility, the xz degrees of freedom of the left front wheel of the whole vehicle are constrained, the xyz degrees of freedom of the right front wheel are constrained, the z-direction degree of freedom of the rear wheels is constrained, the left front and right rear tires are raised by 150 mm, and a vertical acceleration of -1g is applied to the whole frame; when calculating the braking flexibility, no constraints are applied to the frame. A vertical self-weight of -1g and a dynamic load coefficient of -1g in the x-direction are applied to the whole frame, the reaction forces of each tire are calculated, and then the reaction forces are applied to the tire contact points, and the inertial release method is used for calculation; when calculating the torsional moment of inertia, the z-direction degree of freedom of the center point of the front axle is constrained, the xyz-direction degrees of freedom of the connection between the rear leaf spring and the rear axle are constrained, and a concentrated force load of ±10,000 N in the vertical direction is applied to the connection between the front leaf spring and the front axle, and the maximum displacement L of the loading point is calculated; the calculation method of the torsional moment of inertia is: the product of the front axle torque and the wheelbase, divided by the product of the shear modulus and the torsional angle of the left and right loading points; when performing modal calculation, the Lanzcos method is used and the frequency range is set to 0 - 100 Hz to perform modal analysis on the frame.

[0013] In an embodiment of the present application, a multi-objective optimization design method for a light truck frame is provided, which is characterized by including: establishing a finite element model of the light truck frame; determining the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub-working condition; performing multi-condition and multi-objective topology optimization on the finite element model according to the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub-working condition; performing a main effect analysis on the light truck frame; performing multi-objective size optimization calculation on the light truck frame; and comparing the performance of the light truck frame before and after optimization. Through multi-condition and multi-objective topology optimization and multi-objective size optimization, the high-strength lightweight design of the light truck frame is completed, effectively improving the static and dynamic performance of the frame; through multi-objective structural optimization, the comprehensive average stiffness and the first-order average dynamic frequency performance of the frame are improved on the original basis, while the frame mass is reduced. Under the condition of improving the frame performance, the multi-objective structural optimization and lightweight of the frame are finally completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present invention and, together with the specification, are used to explain the principles of the present invention.

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings required for describing the embodiments or the prior art will be briefly introduced below. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a schematic flow chart of a multi-objective optimization design method for a light truck frame provided according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0018] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of this application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of this application described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily limit to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0019] As described in the background art, when optimizing and analyzing a light truck frame, generally corresponding performance calculations are carried out according to each single discipline, and then optimization is carried out according to each target value. Each performance calculation and optimization direction is independent and incomplete, and one-sided, and it is impossible to comprehensively optimize the optimal performance, so it is impossible to obtain the optimal cross-sectional thickness, minimum frame mass, minimum turning flexibility, maximum first-order dynamic frequency, etc. based on all performances.

[0020] The lightweight optimization of a light truck frame mainly includes three categories. One is to use lightweight materials, the second is to use advanced manufacturing processes, and the third is to improve its structure to reduce the frame mass. In order to improve the frame safety, generally, structural optimization research will be carried out on the improved frame to improve the frame stiffness, dynamic frequency and other performances. Frame structure optimization methods include topology optimization, size optimization, single-objective optimization, multi-objective optimization, etc.

[0021] For the multi-disciplinary and multi-objective category mainly involving the finite element static analysis, modal and structural optimization design of the frame, the overall design process of the light truck frame becomes very complicated, and the multi-objective optimization design method will bring a very convenient solution to the design of the light truck frame, which is of great significance in improving the frame performance, solving key technologies, lightweight, cost reduction and reducing the project development cycle.

[0022] In order to improve the safety and driving range of the light truck frame and reduce the energy consumption of the whole vehicle, aiming at improving the frame stiffness and low-order dynamic frequency of the light truck, the optimal stress structure of the frame is determined through multi-condition and multi-objective topology optimization. In order to minimize the frame mass as much as possible while improving the performance, multi-objective size optimization is carried out on the frame after multi-condition and multi-objective topology optimization, and finally the high-strength and lightweight design of the light truck frame is completed.

[0023] As Figure 1 shown, the embodiments of this application provide a multi-objective optimization design method for a light truck frame, including:

[0024] S1 Establish a finite element model of the light truck frame;

[0025] S3 Determine the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - condition;

[0026] S6 Perform multi - condition and multi - objective topology optimization on the finite element model according to the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - condition;

[0027] S9 Conduct the main effect analysis of the light truck frame;

[0028] S12 Perform multi - objective size optimization calculation on the light truck frame;

[0029] S15 Compare the performance of the light truck frame before and after optimization.

[0030] Through multi - condition and multi - objective topology optimization and multi - objective size optimization, the high - strength lightweight design of the light truck frame is completed, effectively improving the static and dynamic performance of the frame; through multi - objective structural optimization, the comprehensive average stiffness and the first - order average dynamic frequency performance of the frame are improved on the original basis, while the frame mass is reduced. Under the condition of improving the frame performance, the multi - objective structural optimization and lightweight of the frame are finally completed.

[0031] Establishing a finite element model of the light truck frame includes: determining the geometric digital models of the longitudinal beam, cross beam and their connecting plates of the light truck frame, the brackets directly connected to the frame, the suspension system, the axle and the tires, performing pre - processing on the model, and converting the geometric model into a discrete finite element model.

[0032] The calculation of static and dynamic working conditions and the weight coefficients of each sub - condition can include: determining the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - condition, calculating the weight coefficients of each sub - condition through the orthogonal analysis method, and obtaining the reference ratio of the importance degree between each working condition. Combining with the matching of each sub - condition, the general form of the importance degree judgment matrix of static and dynamic sub - conditions is obtained. When comparing each sub - condition pairwise, if the judgment matrix eigenvalues and eigenvectors are inconsistent with the importance degree evaluation of each working condition, generally, the modified consistency index is used to judge its consistency. For the judgment matrix that meets the consistency requirement, the maximum eigenvalue and the corresponding eigenvector are obtained, and the eigenvector is normalized to obtain the weight coefficients of each static and dynamic sub - condition in the multi - condition and multi - objective topology optimization of the light truck frame. In order to improve the frame stiffness and low - order dynamic frequency performance, the bending flexibility, torsional flexibility, turning flexibility, braking flexibility and the first 5 - order dynamic frequencies of the frame are selected for multi - condition and multi - objective topology optimization. Obtain the importance degree judgment matrix of static and dynamic sub - conditions. Calculate the maximum eigenvalue of the matrix, and obtain the static and dynamic working conditions of the frame and the weight coefficients of each sub - condition according to the eigenvector and the national standard.

[0033] Multi - condition and multi - objective topology optimization includes: determining the installation positions of some assemblies, mainly optimizing the positions of the frame cross - members and the punching positions of the longitudinal beams. The frame material mainly uses 610L with a yield strength of 500 MPa, and the members are connected by welding or node coupling. Based on the frame, 10 - mm quadrilateral shell elements are used for mesh division, and local complex structures are refined by triangular elements to establish a multi - condition and multi - objective topology optimization design space. Taking the relative density of the frame design area unit as the design variable, the volume fraction of the design area as the constraint, and the minimum static compliance and the maximum low - order dynamic frequency of the frame under multiple conditions as the objectives, a multi - condition and multi - objective topology optimization mathematical model of the light - truck frame is obtained through the variable density method combined with the compromise programming method, the average frequency formula, and the efficacy coefficient method. Among them, the static and dynamic conditions and the weight coefficients of each sub - condition have been calculated by the orthogonal analysis method. The maximum and minimum compliance functions of the light - truck frame under the static sub - condition and the maximum and minimum frequency functions of the low - order frequency band under the dynamic sub - condition are obtained by single - condition optimization. The multi - condition and multi - objective topology optimization function of the frame is defined through the dequtions module in OptiStruct combined with each response. In order to obtain clearer results, manufacturing process constraints are added during the optimization process. The objective function converges after 58 iterations, obtaining the iteration process of the frame compliance sub - condition, the iteration process of the frame frequency sub - condition, the iteration process of the frame objective function, and the multi - condition and multi - objective topology optimization result of the frame. To further improve the static and dynamic performance of the light - truck frame and minimize the frame mass as much as possible, multi - objective size optimization is carried out on the frame with improved structure based on the main - effect analysis and the global response surface method (GRSM).

[0034] The main - effect analysis calculation of the frame includes:

[0035] According to the structural symmetry of the light - truck frame and the cross - section thickness of the cross - members, the cross - members of the frame are grouped into variables, a total of 20 groups, denoted as T1, T2, …, T20 respectively. Taking the mass, turning compliance, and first - order dynamic frequency of the light - truck frame as the design responses, the main - effect analysis of the mass, turning compliance, and first - order dynamic frequency of the frame design variable group is carried out through the design of experiments (DOE) in HyperStudy. Design variables such as T1, T2, T4, T5, T19, etc. contribute more than 70% to the turning compliance and the first - order dynamic frequency of the frame, with a greater impact, and each design variable is negatively correlated with the turning compliance or positively correlated with the first - order dynamic frequency. Optimizing them will reduce the frame performance, so they are not optimized. In order to reduce the frame mass while improving the performance, the remaining design variables are selected for multi - objective size optimization.

[0036] The multi - objective size optimization calculation of the frame includes:

[0037] Taking the cross-sectional thickness of each group of design variables selected after the main effect analysis as the optimization variables, with the goals of minimizing the frame mass, minimizing the turning flexibility, and maximizing the first-order dynamic frequency, the multi-objective size optimization of the frame is carried out by the global response surface method (GRSM). An optimization mathematical model is established. When performing multi-objective optimization, the improvement of one objective will cause the decline of another objective. It is necessary to make a trade-off between feasible solutions according to the design requirements to obtain a compromise solution for each objective. The interval of all feasible solutions is the Pareto front. In the Pareto front, the solution that can improve the static and dynamic performance of the frame and has the smallest possible mass is used as the optimal solution for the multi-objective size optimization of the final frame. The frame is set and solved through HyperStudy and OptiStruct to obtain the Pareto front. The trade-off optimal solution is obtained, and the sizes and rounded values of each optimization variable before and after optimization are obtained. The values of the frame cross-sectional thickness before optimization, after optimization, and after rounding are obtained. Substitute the rounded value of the trade-off optimal solution into the optimized frame, and analyze and compare the static and dynamic performance of the frame before and after optimization.

[0038] The performance comparison of the frame before and after optimization includes:

[0039] Static analysis, modal analysis, etc. are carried out on the original light truck frame and the frame after multi-condition and multi-objective topology optimization and multi-objective size optimization to obtain the frame constraints. Among them, for the calculation of bending flexibility, the xz degrees of freedom of the left front wheel of the whole vehicle are constrained, the xyz degrees of freedom of the right front wheel are constrained, and the z-direction degree of freedom of the rear wheels is constrained. The constraint position is at the tire contact point. The overall frame is applied with a vertical downward dynamic load coefficient of 3.5g to achieve this. Among them, for the calculation of turning flexibility, the xz degrees of freedom of the left front wheel of the whole vehicle are constrained, the z-direction degree of freedom of the right front wheel is constrained, and the z-direction degree of freedom of the rear wheels is constrained. One end of the frame grounding spring connected to the ground is constrained by 2. The overall frame is applied with a self-weight acceleration of -1g in the vertical direction and a dynamic load coefficient of 0.5g in the lateral direction. Among them, for the calculation of torsional flexibility, the xz degrees of freedom of the left front wheel of the whole vehicle are constrained, the xyz degrees of freedom of the right front wheel are constrained, and the z-direction degree of freedom of the rear wheels is constrained. The left front and right rear tires are raised by 150 mm. The overall frame is achieved by applying an acceleration of -1g in the vertical direction. Among them, when calculating the braking flexibility, no constraints are applied to the frame. The overall frame is applied with a vertical self-weight of -1g and a dynamic load coefficient of -1g in the x-direction. The reaction forces of each tire are calculated, and then the reaction forces are applied to the tire contact points, and the inertial release method is used for calculation. When calculating the torsional moment of inertia, the z-direction degree of freedom of the center point of the front axle is constrained, and the xyz-direction degrees of freedom of the connection between the rear leaf spring and the rear axle are constrained. A concentrated force load of ±10,000 N in the vertical direction is applied to the connection between the front leaf spring and the front axle. The maximum displacement L of the loading point is calculated. The calculation method of the torsional moment of inertia is: the product of the front axle torque and the wheelbase, divided by the product of the shear modulus and the torsional angles of the left and right loading points. When performing modal calculation, the Lanzcos method is used and the frequency range is set to 0 - 100 Hz to perform modal analysis on the frame; the static and dynamic performance analysis results before and after the frame optimization are converted into a comparison of the static and dynamic performance and mass before and after the frame optimization. It is obtained that the deformation displacement and stress of the frame are the largest in the turning condition, and the maximum deformation and maximum stress do not exceed the material usage range. After the frame undergoes multi-condition and multi-objective topology optimization and multi-objective size optimization, the maximum deformation, maximum stress, displacement, and stress of the frame are all reduced, and the performance is improved to a certain extent. Compared with the original frame, the new frame has better structural performance and meets the design requirements. After optimization, the comprehensive average stiffness of the frame in typical conditions is improved, the 1st-order comprehensive average dynamic frequency is improved, and the frame mass is reduced, completing the high-strength lightweight design of the light truck frame.

[0040] This application establishes a finite element model of a light truck frame, constructs a multi-condition and multi-objective topology optimization space based on the original vehicle frame, determines the static and dynamic conditions and the weight coefficients of each sub-condition through the orthogonal analysis method, takes the relative density of the design space unit as the design variable, and aims at minimizing the static compliance and maximizing the low-order dynamic frequency of the frame under multiple conditions, and conducts multi-condition and multi-objective topology optimization on the frame. The frame structure is improved according to the topology optimization results, variable grouping and main effect analysis are carried out on the improved frame, and the design variables that are negatively correlated with the turning compliance of the frame, positively correlated with the first-order dynamic frequency and have a large value are removed. Taking the cross-sectional thickness of the remaining design variables as the optimization variables, and aiming at minimizing the frame mass, minimizing the turning compliance and maximizing the first-order dynamic frequency, multi-objective size optimization is carried out on the improved frame. Static analysis and modal analysis are carried out on the frame before and after optimization. After optimization, the comprehensive average stiffness of the frame is improved, the first-order average dynamic frequency is increased, and the frame weight is reduced, completing the high-strength lightweight design of the light truck frame. It provides a reliable analysis method for the comprehensive performance and lightweight design of the frame, thereby improving the product development efficiency, reducing the development cost, shortening the project cycle, and is of great significance to the performance optimization design and lightweight in the development of light trucks.

[0041] The serial numbers of the above embodiments of this application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0042] If the integrated unit in the above embodiments is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in the above computer-readable storage medium. Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in the storage medium and includes several instructions for causing one or more electronic devices (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0043] In the above embodiments of this application, the descriptions of the various embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0044] In several embodiments provided by this application, it should be understood that the disclosed client can be implemented in other ways. Among them, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling, direct coupling or communication connection to each other can be through some interfaces. The indirect coupling or communication connection of units or modules can be in electrical or other forms.

[0045] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution provided in this embodiment.

[0046] In addition, in each embodiment of this application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0047] In the above embodiments of this application, the descriptions of each embodiment have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0048] The above are only the preferred embodiments of this application. It should be noted that for those of ordinary skill in the art, without departing from the principle of this application, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of this application.

Claims

1. A multi-objective optimization design method for a light truck frame, characterized in that, Including: Establishing a finite element model of a light truck frame; Determining the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition; Performing multi - condition and multi - objective topology optimization on the finite element model according to the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition; Conducting a main effect analysis of the light truck frame; Performing multi - objective dimension optimization calculation of the light truck frame; Comparing the performance of the light truck frame before and after optimization.

2. The multi-objective optimization design method of the light truck frame according to claim 1, characterized in that The establishment of the finite element model of the light truck frame includes: Determining the geometric digital models of the longitudinal beams, cross beams and connecting plates of the light truck frame, brackets directly connected to the frame, suspension systems, axles and tires; Performing pre - processing on the geometric digital models and converting them into discrete finite element models.

3. The multi-objective optimization design method for the light truck frame according to claim 1, characterized in that The determination of the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition includes: Determining the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition; Calculating the weight coefficients of each sub - working condition according to the orthogonal analysis method to obtain the reference ratio of the importance degree between each sub - working condition.

4. The multi-objective optimization design method of the light truck frame according to claim 3, characterized in that, The determination of the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition also includes: Performing pairwise matching comparison on each sub - working condition; Judging whether the eigenvalue and eigenvector of the judgment matrix are consistent in evaluating the importance degree of each working condition; If the eigenvalue of the matrix and the eigenvector are consistent in evaluating the importance degree of each working condition, determining the maximum eigenvalue of the matrix and the corresponding eigenvector, and performing normalization processing on the eigenvector to obtain the weight coefficients of each static and dynamic sub - working condition in the multi - condition and multi - objective topology optimization of the light truck frame; Selecting bending flexibility, torsional flexibility, turning flexibility, braking flexibility and the first 5 - order dynamic frequencies of the frame to perform multi - condition and multi - objective topology optimization on the light truck frame to obtain a judgment matrix of the importance degree of static and dynamic sub - working conditions; Determining the maximum eigenvalue and the corresponding eigenvector of the judgment matrix of the importance degree of the static and dynamic sub - working conditions, and determining the final static and dynamic working conditions of the frame and the final weight coefficients of each sub - working condition according to the eigenvector.

5. The multi-objective optimization design method of the light truck frame according to claim 1, characterized in that, The multi - condition and multi - objective topology optimization of the finite element model according to the static and dynamic working conditions of the light truck frame and the weight coefficients of each sub - working condition includes: Establishing a multi - condition and multi - objective topology optimization design space; Taking the relative density of the design area units of the light truck frame as the design variable, the volume fraction of the design area as the constraint, and the minimum static flexibility and the maximum low - order dynamic frequency of the frame multi - condition as the objectives, and defining through the variable density method combined with the compromise programming method, the average frequency formula and the efficacy coefficient method to obtain the multi - condition and multi - objective topology optimization mathematical model of the light truck frame; Determining the maximum flexibility function and the minimum flexibility function under the static sub - working conditions of the light truck frame by single - condition optimization, and obtaining the maximum and minimum frequency functions of the low - order frequency band under the dynamic sub - working conditions; Defining the multi - condition and multi - objective topology optimization function of the frame through the dequti ons module in Opti Struct combined with each response.

6. The multi-objective optimization design method for the light truck frame according to claim 1, characterized in that, The main effect analysis of the light truck frame includes: Grouping variables of the frame cross beams according to the structural symmetry of the light truck frame and the cross - section thickness of the cross beams; Taking the frame mass, turning flexibility, and first-order dynamic frequency of a light truck as design responses, perform a main effect analysis of the frame design variable groups for mass, turning flexibility, and first-order dynamic frequency through Design of Experiments (DOE) in HyperStudy; Judge whether the contribution degrees of multiple grouped design variables to the turning flexibility and first-order dynamic frequency of the frame are higher than a preset value; If there are groups among the multiple grouped design variables whose contribution degrees to the turning flexibility and first-order dynamic frequency of the frame are higher than the preset value, and the grouped design variables with contribution degrees higher than the preset value are negatively correlated with the turning flexibility, or positively correlated with the first-order dynamic frequency, then perform multi-objective size optimization on the grouped design variables with contribution degrees not higher than the preset value.

7. The multi-objective optimization design method for the light truck frame according to claim 6, characterized in that, Performing the multi-objective size optimization calculation of the light truck frame includes: Set the cross-sectional thickness of the grouped design variables with contribution degrees not higher than the preset value as the optimization variables, and perform multi-objective size optimization on the frame through the Global Response Surface Method (GRSM) with the goals of minimizing the frame mass, minimizing the turning flexibility, and maximizing the first-order dynamic frequency; Establish an optimization mathematical model; Obtain the values of the frame cross-sectional thickness before optimization, after optimization, and after rounding. Substitute the rounded value of the compromise optimal solution into the optimized frame, and analyze and compare the static and dynamic performances of the frame before and after optimization.

8. The multi-objective optimization design method for the light truck frame according to claim 1, characterized in that Comparing the performances of the light truck frame before and after optimization includes: Perform static analysis, modal analysis, etc. on the original light truck frame and the frame after multi-condition multi-objective topology optimization and multi-objective size optimization to obtain the frame constraints.

9. The multi-objective optimization design method of the light truck frame according to claim 8, characterized in that, Comparing the performances of the light truck frame before and after optimization also includes: When calculating the bending flexibility, constrain the xz degrees of freedom of the left front wheel of the whole vehicle, the xyz degrees of freedom of the right front wheel, and the z-direction degree of freedom of the rear wheels. The constraint position is at the tire contact point, and apply a vertical downward dynamic load coefficient of 3.5g to the whole frame; When calculating the turning flexibility, constrain the xz degrees of freedom of the left front wheel of the whole vehicle, the z-direction degree of freedom of the right front wheel, and the z-direction degree of freedom of the rear wheels. Constrain 2 at one end of the frame grounding spring connected to the ground, and apply a vertical self-weight acceleration of -1g and a lateral dynamic load coefficient of 0.5g to the whole frame; When calculating the torsional flexibility, constrain the xz degrees of freedom of the left front wheel of the whole vehicle, the xyz degrees of freedom of the right front wheel, and the z-direction degree of freedom of the rear wheels. Raise the left front and right rear tires by 150 mm, and apply an acceleration of -1g in the vertical direction to the whole frame; When calculating the braking flexibility, no constraints are applied to the frame. Apply a vertical self-weight of -1g and a dynamic load coefficient of -1g in the x-direction to the whole frame, calculate the reaction forces of each tire, and then apply the reaction forces to the tire contact points and calculate using the inertial release method; When calculating the torsional moment of inertia, constrain the z-direction degree of freedom of the center point of the front axle, and constrain the xyz directions of freedom at the connection between the rear leaf spring and the rear axle. Apply a concentrated force load of ±10000 N in the vertical direction at the connection between the front leaf spring and the front axle, and calculate the maximum displacement L of the loading point; The calculation method of the torsional moment of inertia is: the product of the front axle torque and the wheelbase, divided by the product of the shear modulus and the torsional angle of the left and right loading points; When performing modal calculations, the Lanzcos method is used and the frequency range is set to 0 - 100 Hz to perform modal analysis on the vehicle frame.

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