基于拓扑与形状优化的小型化金属天线设计方法

天线小型化设计需要基于先进的设计方法,基于拓扑优化的设计往往存在灰度单元,因此设计结果无法直接应用,需要进一步规整设计。而对于电磁金属结构,粗糙的规整方法会引起结构性能的很大变化以致偏离最优结果。提出一种拓扑优化和形状优化相结合的方法,用于金属天线结构的小型化设计。该方法通过拓扑优化获得金属天线结构的概念构型,进而利用形状优化对概念构型进行边界规整和精细化设计。形状优化方法采用多控制点贝塞尔曲线描述拓扑概念构型,通过贝塞尔曲线控制点的移动实现天线构型的调控。给出了贝塞尔曲线控制点的设置原则,基于拓扑优化得到场量分布结果,利用较少的贝塞尔曲线控制点实现天线拓扑构型结构特征的有效调控。该方法可以获得无灰度单元残留的拓扑结果,同时可有效避免密度阈值规整方法中天线性能改变的问题,并且获得的拓扑构型边界光滑。数值算例表明拓扑优化和形状优化相结合方法的有效性。此外,该方法可拓展到其他类型电磁器件的优化设计中。     

基于IGA-SIMP法的连续体结构应力约束拓扑优化

建立了一种IGA-SIMP框架下的连续体结构应力约束拓扑优化方法。基于常用的SIMP模型,将非均匀有理B样条（NURBS）函数用于几何建模、结构分析和设计参数化,实现了结构分析和优化设计的集成统一。利用高阶连续的NURBS基函数,等几何分析（IGA）提高了结构应力及其灵敏度的计算精度,增加了拓扑优化结果的可信性。为处理大量局部应力约束,提出了基于稳定转换法修正的P-norm应力约束策略,以克服拓扑优化中的迭代振荡和收敛困难。通过几个典型平面应力问题的拓扑优化算例表明了本文方法的有效性和精确性。应力约束下的体积最小化设计以及体积和应力约束下的柔顺度最小化设计的算例表明,基于稳定转换法修正的约束策略可以抑制应力约束体积最小化设计中的迭代振荡现象,获得稳定收敛的优化解;比较而言,体积和应力约束下的柔顺度最小化设计的迭代过程更加稳健,适合采用精确修正的应力约束策略。     

The nominal force method for truss geometry and topology optimization incorporating stability considerations

This paper presents a computationally efficient method for truss layout optimization with stability constraints. Previously proposed approaches that ensure stability of optimal frameworks are first reviewed, showing that existing studies are generally restricted to topology optimization. The present contribution aims to generalize the approach to simultaneous geometry and topology optimization. A lower-bound plastic design formulation under multiple loading will serve as basis for this purpose. The numerical difficulties associated with geometrical variations are identified and the parametrization is adapted accordingly. To avoid nodal instability, the nominal force method is adopted, which introduces artificial loading cases to simulate the effect of geometric imperfections. Hence, the truss systems with unstable nodes are eliminated from the set of optimal solutions. At the same time, the local stability of structural members is ensured via a consistent local buckling criterion. This novel formulation leads to optimal configurations that can be practically used for the preliminary design of structural frameworks. Four applications illustrate the impact of stability constraints on the solution. The importance of geometry optimization is also pointed out by comparing with results that would be unattainable by topology optimization only.     

应用于非凸设计区域桁架拓扑优化的一种基结构生成方法

为了提高桁架拓扑优化设计中非凸区域生成基结构的效率和准确性,介绍了一种基于几何和网格信息生成初始基结构的方法。通过直接将已有几何边界作为碰撞检测的标准,避免对原有边界扩展或构建限制区域,简化了基结构生成过程并可以避免杆件识别不准确的问题;通过减少需要与凹边界碰撞检测的杆件个数来提升整体基结构的生成效率;最后,针对已生成的基结构进行基于塑性准则的桁架拓扑优化。     

新一代大射电望远镜馈源舱索支撑系统的优化设计

基于对馈源舱姿态由40°增加到60°的设计要求,本文首先将原来的等高塔改成两组不等高塔,这对确保馈源舱60°姿态角的实现起到了关键作用。其次,对舱索支撑系统进行了优化设计。设计参数包括索与馈源舱的连接点坐标、索横截面积、塔高等物理量,约束函数为平衡方程、材料强度及边界条件,目标是使索张力差最小。再者,增加平衡重,且平衡重离舱顶端距离可在整个工作空间内实时改变,这不仅有利于舱姿态角的实现,而且可使索张力差进一步减小。最后,通过大量的数值计算和LT5m实验,结果证明了本文所提模型方法和措施的可行性与有效性。     

基于深度学习的跨分辨率结构拓扑优化设计方法

在传统拓扑优化设计中,随着结构单元增加,迭代计算过程消耗了大量的时间.本文提出了一种基于深度学习的方法来加速拓扑优化设计过程,缩短了结构拓扑优化设计的迭代过程,并生成了高分辨率拓扑优化结构.利用深度学习方法,在低分辨率中间构型与高分辨率拓扑构型之间创建高维映射关系,利用独立、连续和映射(ICM)方法建立深度学习网络所需...     

车身结构中焊点布置的分区拓扑优化设计方法研究

焊点布置的设计对于车身结构的强度、刚度、NVH特性和耐撞性等都有重要影响。针对一种紧凑型两厢轿车,分别以车身结构的刚度和低频固有振动特性为设计目标,对车身结构中的焊点布置进行了优化设计。通过对优化设计结果的理论分析和工程评价,对相关的优化设计问题定义的有效性和优化设计方法的适用性进行了分析。基于相关分析结论和车身结构设计经验,提出了一种新的车身结构焊点布置的分区拓扑优化设计方法,通过将车身划分为多个功能设计区域,可以采用分级优化设计的方法综合考虑车身结构的刚度和动态特性、耐撞性以及强度等多方面的性能要求。通过对一个实际轿车车身结构中焊点布置的重新优化设计,验证了提出的优化设计方法的有效性,同时表明该车身的现有焊点布置方案已接近最优设计。     

Using a virtual skeleton to increase printability of topology optimized design for industry-class applications

This article broadens the scheme previously developed to associate topology optimization with additive manufacturing through the use of a virtual skeleton, consisting in solving the same physical problem with a discrete approach and then with a continuum one. This procedure for 3D designs is applied to various domain geometries, to demonstrate its pertinence on high-resolution industrial cases. An algorithm searching for the best printing direction, exploring the solid angle, is also described and validated; the surface-shaped presentation of the result allows immediate understanding of the influence of the discrete problem parameters, while its running time is much lower than a unique continuum optimization simulation, which proves the attractiveness of the method. In the three examples studied, the procedure outputs exhibit greater printability than the ones produced by traditional methods in each of the printing direction tested, albeit responsibility is left to the final user to choose his best trade-off. Furthermore, the unprintable zones are readily displayed to be either reworked or supported. Explanations about increase of convergence likelihood on discrete structures despite the geometry complexity of an industrial application are also provided and demonstrated.     

基于实验设计法的工程结构优化设计

基于实验设计法,提出了一种新的工程结构优化设计方法,这种方法将设计变量的水平值配列于正关表中,按正交表的参数组合条件进行结构解析,通过对设计变量对于目标函数值的方差分析和F检验,改变设计变量的水平值,进而通过迭代计算使设计变量趋地最优解,本文以杵架结构为计算例,验证了本方法的全局收敛性和优化精度,由于无需构建目标函数和约束函数以及微分计算,此方法具有简单而又适应广泛的优点。     

强爆炸冲击波作用下天线结构的离散变量优化设计

首先建立了强爆炸冲击波作用下天线结构受精度和应力约束的连续变量优化设计数学模型 ;其次 ,根据材料特点 ,将设计变量取为离散变量 ,提出了天线结构在强爆炸冲击波作用下受精度和应力约束的离散变量优化设计数学模型。采用离散变量优化算法离散复合形法 ,对强爆炸冲击波作用下的 8m天线进行了优化计算。结果表明 ,经优化设计后 ,天线重量仅为初始重量的 4 0 %。     

An explicit level set approach for generalized shape optimization of fluids with the lattice Boltzmann method

This study is concerned with a generalized shape optimization approach for finding the geometry of fluidic devices and obstacles immersed in flows. Our approach is based on a level set representation of the fluid–solid interface and a hydrodynamic lattice Boltzmann method to predict the flow field. We present an explicit level set method that does not involve the solution of the Hamilton–Jacobi equation and allows using standard nonlinear programming methods. In contrast to previous works, the boundary conditions along the fluid–structure interface are enforced by second‐order accurate interpolation schemes, overcoming shortcomings of flow penalization methods and Brinkman formulations frequently used in topology optimization. To ensure smooth boundaries and mesh‐independent results, we introduce a simple, computationally inexpensive filtering method to regularize the level set field. Furthermore, we define box constraints for the design variables that guarantee a continuous evolution of the boundaries. The features of the proposed method are studied by two numeric examples of two‐dimensional steady‐state flow problems. Copyright © 2009 John Wiley & Sons, Ltd.     

针对注塑成型随形冷却的流热力耦合拓扑优化方法研究

注塑成型在塑料工业生产中占据重要地位,注塑模具的散热能力影响着塑料制品的生产效率以及产品质量.本文基于变密度拓扑优化方法,以最小化结构平均温度为目标,研究了注塑模具冷却管道的拓扑优化问题.由于在注塑成型过程中模具会受到注塑机施加的克服塑件胀模力的巨大锁模力,故本文还将模具结构承载性能作为优化的评价指标.最终基于开源平台...     

基于77GHz毫米波雷达接收天线的周期性条形阵列解耦结构优化方法

阵列天线是77 GHz毫米波雷达的核心硬件之一,其天线性能决定着雷达的探测能力。由于工作频率的升高以及毫米波雷达小型化、集成化的发展趋势,使得雷达阵列天线阵元间距过密,从而相互干扰出现强互耦效应,严重恶化雷达阵列天线的性能。为了解决上述问题,本文提出了一种基于77 GHz毫米波雷达接收天线的周期性条形阵列解耦结构优化方法。该方法通过优化周期性条形阵列解耦结构单元的条形厚度和间距,在保证阵列天线辐射性能的基础上,来抑制毫米波雷达接收天线阵元间的互耦并提高其阵元间的隔离度。仿真结果表明,相比于无解耦结构的阵列天线,提出的解耦结构能够有效地降低毫米波雷达接收天线间的耦合,尤其在中心频率77.75 GHz处互耦减少了13.29 dB。在施加周期性条形阵列解耦结构前后,阵列天线均在77.5 GHz～78.5 GHz指定频段内正常工作,且合成辐射方向图的最大增益几乎保持不变,从而保证了毫米波雷达阵列天线的辐射性能。典型的数值算例能够很好地验证所提方法的有效性。     

Airfoil design optimization based on lattice Boltzmann method and adjoint approach

We present a new aerodynamic design method based on the lattice Boltzmann method (LBM) and the adjoint approach. The flow field and the adjoint equation are numerically simulated by the GILBM (generalized form of interpolation supplemented LBM) on non-uniform meshes. The first-order approximation for the equilibrium distribution function on the boundary is proposed to diminish the singularity of boundary conditions. Further, a new treatment of the solid boundary in the LBM is described particularly for the airfoil optimization design problem. For a given objective function, the adjoint equation and its boundary conditions are derived analytically. The feasibility and accuracy of the new approach have been perfectly validated by the design optimization of NACA0012 airfoil.     

An sequential optimization and aeroelastic constraint transformation method for strength-aeroelastic comprehensive design

With the development of modern aircraft technology, aeroelasticity plays a more and more crucial role in aircraft structural design. However, low efficiency of present aeroelastic analysis and optimization methods makes it difficult to apply in engineering practice. This paper presents a sequential optimization and aeroelastic constraint transformation method (SOACTM) for comprehensive design of airplane wings with strength and aeroelastic constraints. Optimization with structural strength constraint and aeroelastic constraint is transformed into a serial of cycles of decoupled structural strength sub-optimizations and aeroelastic sub-optimizations based on sequential optimization strategy. In structural strength sub-optimization, structural strength constraint is translated along its normal direction to make optimal design point satisfying aeroelastic constraint. And the goal of aeroelastic sub-optimization is to find the translational distance of structural strength constraint. Aeroelastic constraint is transformed to equivalent structural strength constraint via above approach. In this way, number of aeroelastic analyses in SOACTM is less than that in traditional optimization method and total computational time decreases. SOACTM is verified based on two examples. Traditional optimization method is applied for the sake of validation. The results demonstrated the accuracy and efficiency of SOACTM for wing comprehensive optimization considering both structural strength and aeroelastic constraints.     

基于参数化水平集方法的微结构拓扑优化设计

相比于单一材料,复合材料具有轻质高强等优点,拓扑优化方法是设计复合材料的方法之一.本文采用改进的参数化水平集方法,更新了水平集迭代格式,并应用水平集带方法在优化过程中引入中间密度,使水平集方法与变密度法无缝结合以改善水平集方法的拓扑寻优能力,降低其初始设计依赖性.本文以最大化体积模量、剪切模量和负泊松比作为材料设计目标...     

基于综合非线性优化方法的倒张型悬索桥非线性优化设计

提出随机优化、零阶优化和一阶优化相结合的综合非线性优化方法,并通过对ANSYS程序的二次开发编制全面优化设计和非线性有限元分析的综合辅助程序,从而对倒张型悬索桥进行非线性优化设计,以更合理地确定倒张型悬索桥设计中的关键因素,最终使倒张型悬索桥的受力和变形达到均匀合理的状态,以利于实际工程设计和应用.从优化设计前后的对比可以看出,本文的综合非线性优化方法和综合辅助程序简单有效,优化的效果显著.     

基于CAD平台的周期性材料单胞的参数化形状优化设计方法

对于具有特定材料属性的周期性复合材料设计,提出了一种参数化的形状优化方法。对于带有周期性结构的两相材料,给定细观单胞结构的基本构型,通过参数化的实体造型技术,结合均匀化方法,实现了通用的材料单胞形状参数化设计方法,以获取指定材料性能。在参数化结构形状优化设计CAD/CAE集成平台POSHAPE上完成程序实现。文中算例给出了两相蜂窝型骨架复合材料和空心复合材料周期性单胞的零泊松比和指定参数性质的形状优化设计过程,并验证了本文方法的有效性。