Multi-mesh and adaptivity in 3D shape optimization

The major drawback in three-dimensional shape optimization is the excessive computational time needed in spite of the use of parametric-type design variables. Therefore, in addition to parametrization we suggest the use of several meshing levels to speed up the obtention of the optimal solution and to check the precision of the analysis by an error estimation. The combination of parametrization, multi-mesh and error estimation allows us to deal efficiently with three-dimensional shape optimization problems.     

Optimal shape design for contact problems

A new optimization problem of controlling the contact pressurep is presented. We seek the minimum of the maximum contact pressurep _max under the following conditions: (a) the contact pressure should satisfy the inequalityp 0 as well as the controlling condition = v(x) p _max –p(x) 0, wherev(x) is the controller function; (b) the gapd between two bodies should be positive or zerod 0 after deformation; (c) at any possible contact point the conditionpd = 0 should be satisfied and the body that is capable of rigid body motion should be in equilibrium.If the gapd = d(p, h) is a linear function of both the pressurep and the contour changeh, then the optimization problem is a linear programming problem of restricted basis exchange. Three algorithms are presented for the solution of this problem. Finally, numerical examples will demonstrate the controlling technique for the shape optimization problem of a roller bearing.     

Optimal shape design of a rotary microactuator

Optimal shape designs of electrodes based on parallel-plate configurations are proposed for an electrostatic rotary microactuator to enhance actuating force generation capability. In most conventional electrostatic microactuators associating parallel-plate configurations with rotary mode, the shape of electrodes have not been rigorously evaluated in terms of optimality and straight shapes were simply adopted. As a result, two facing electrodes are spaced in the way of leading to relatively large clearance at the outer region from the center of rotation; hence force generation capability is inherently limited. To overcome the limitation of conventional rotary microactuators and enhance the capability, a tilting configuration is invoked and integrated into the optimal shape, which allows the gap size between two facing electrodes to be as small as the minimum gap size achievable by current fabrication technology. This study demonstrates that the proposed optimal shape integrating tilting configuration increases the force generation capability dramatically over conventional shapes     

基于NURBS方法的气动外形优化设计

采用NURBS曲线曲面,对钝锥弹头和钝双锥弹体建立参数化曲面模型,取NURBS曲线控制点作为设计参数,应用高超声速面元法求解气动力特性,在给定设计约束下,采用遗传算法进行气动外形优化设计,并对优化结果进行了比较分析。结果表明,采用NURBS方法构造参数化外形,并结合优化技术可方便快速地获得所需最优外形;与应用二次曲线构造参数化外形相比,该方法对弹体形状控制更加灵活,并可局部修改弹头曲线形状。因此,基于NURBS方法发展整套的系统优化设计算法很有现实意义和应用价值。     

Optimal shape design as a material distribution problem

Shape optimization in a general setting requires the determination of the optimal spatial material distribution for given loads and boundary conditions. Every point in space is thus a material point or a void and the optimization problem is a discrete variable one. This paper describes various ways of removing this discrete nature of the problem by the introduction of a density function that is a continuous design variable. Domains of high density then define the shape of the mechanical element. For intermediate densities, material parameters given by an artificial material law can be used. Alternatively, the density can arise naturally through the introduction of periodically distributed, microscopic voids, so that effective material parameters for intermediate density values can be computed through homogenization. Several examples in two-dimensional elasticity illustrate that these methods allow a determination of the topology of a mechanical element, as required for a boundary variations shape optimization technique.     

Optimal design of composite structures for strength and stiffness: an inverse homogenization approach

We introduce a rigorously based numerical method for compliance minimization problems in the presence of pointwise stress constraints. The method is based on new multiscale quantities that measure the amplification of the local stress due to the microstructure. The design method is illustrated for two different kinds of problems. The first identifies suitably graded distributions of fibers inside shaft cross sections that impart sufficient overall stiffness while at the same time adequately control the amplitude of the local stress at each point. The second set of problems are carried out in the context of plane strain. In this study, we recover a novel class of designs made from locally layered media for minimum compliance subject to pointwise stress constraints. The stress-constrained designs place the more compliant material in the neighborhood of stress concentrators associated with abrupt changes in boundary loading and reentrant corners.     

Optimal plastic shape design via the boundary perturbation method

The paper presents the boundary perturbation method as applied to optimal plastic shape design. Perfect plasticity is assumed. The procedure consists of two steps: determination of a class of fully plastic solutions in the limit state (if possible), and then the choice of the optimal shape from among those solutions. Governing equations and boundary conditions for general perturbations of a circular cylinder under internal pressure are derived. Two examples of optimization concern non-circular shapes under plane strain conditions (heads of tension members) and pipes of variable diameter (transition zones). In both cases the minimal volume is the design objective under the constraint of given limit load-carrying capacity.     

Optimal shape design of an electrostatic comb drive inmicroelectromechanical systems

Polynomial driving-force comb drives are synthesized using numerical simulation. The electrode shapes are obtained using the indirect boundary element method. Variable-gap comb drives that produce combinations of linear, quadratic, and cubic driving-force profiles are synthesized. This inverse problem is solved by an optimization procedure. Sensitivity analysis is carried out by the direct differentiation approach (DDA) in order to compute design sensitivity coefficients (DSCs) of force profiles with respect to parameters that define the shapes of the fingers of a comb drive. The DSCs are then used to drive iterative optimization procedures. Designs of variable-gap comb drives with linear, quadratic, and cubic driving force profiles are presented in this paper     

Optimum shape design of truss structures based on reliability

A procedure is presented for the shape optimization of truss structures based on the reliability concept. Nodal coordinates are taken as the shape design variables together with the sizing design variables such as the cross-sectional areas of the members. These variables are determined to minimize the structural volume under the constraint on the structural failure probability.     

基于SS序列集成电路不规则模块布图算法

针对Single-Sequence的集成电路布图,在SS编解码应用对芯片中各单元的摆放进行优化,从而达到芯片面积利用率最大化.重点介绍了利用SS序列解决不规则模块摆放问题,使得SS布图功能更灵活多变.     

基于激光雷达传感器的RBPF-SLAM系统优化设计

针对传统Rao-Blackwellized粒子滤波(RBPF)方法的同步定位和建图(SLAM)问题,提出了一种基于激光雷达的RBPF-SLAM系统优化方法,利用高精度激光雷达数据,修正了基于里程计读数的建议分布函数,减少了滤波过程所需的粒子数目;引入了自适应重采样机制,缓解由于重采样带来的粒子消耗问题.为验证改进算法性能,在搭建的差速型移动机器人平台上,进行了验证试验,结果表明:改进后的RBPF-SLAM方法,能够实时构建栅格地图,在建图效率和精度上均有明显的提升.     

基于遗传算法的城市公交骨架线网优化设计

针对现有城市公交线网设计时普遍存在缺乏层次性规划的问题,提出了城市公交骨架网络的布局方法,构建了以线网直达客流密度与线网可达性最大为双目标的公交骨架线网优化模型,设计了一种改进的遗传算法。该算法通过引入动态惩罚系数确定适应度,以调整收敛速度;通过自适应机制确定交叉概率和变异概率,以调整搜索空间。算例分析的结果表明本算法比传统遗传算法具有更好的寻优性能。     

基于I-PSO算法和Simulink的湿式离合器优化设计

为提高湿式离合器的轻便性和可靠性,提出了一种I-PSO算法与MATLAB/Simulink相结合的湿式离合器优化设计新方法。对湿式离合器进行动力学分析,并基于MATLAB/Simulink搭建湿式离合器动力传递的仿真模型。引入模拟退火算法中对粒子进行扰动的思想对改进的粒子群算法再度进行改进,并基于某测试函数验证了算法改进的效果,选择离合器的滑磨功与体积为优化目标。最终联合改进粒子群算法与MATLAB/Simulink中建立的湿式离合器仿真模型对某具体型号湿式离合器进行多目标优化设计。结果表明,改进后的粒子群算法在寻优的速率和精度上有一定效果;优化后的湿式离合器与原设计相比,总目标函数缩小约40.12%,滑磨功减小了约61.8%,优化效果明显。     

基于Memcached的日历搜索引擎系统优化设计与实现

研究基于航信的日历搜索引擎（CS）系统,针对日历搜索引擎系统计算量大、响应速度慢、重复计算的问题,提出了一种利用Memcached对计算单元结果进行缓存的方法,基于此方法对系统架构进行重新设计,并对日历搜索引擎系统进行性能优化。实验结果显示该优化方案减少了系统响应时间,使系统性能得到了大幅度的提升,为民航运价领域中日历搜索引擎系统的优化提供了方法和理论支持。     

Robust aerodynamic shape design based on an adaptive stochastic optimization framework

Optimization techniques combined with uncertainty quantification are computationally expensive for robust aerodynamic optimization due to expensive CFD costs. Surrogate model technology can be used to improve the efficiency of robust optimization. In this paper, non-intrusive polynomial chaos method and Kriging model are used to construct a surrogate model that associate stochastic aerodynamic statistics with airfoil shapes. Then, global search algorithm is used to optimize the model to obtain optimal airfoil fast. However, optimization results always depend on the approximation accuracy of the surrogate model. Actually, it is difficult to achieve a high accuracy of the model in the whole design space. Therefore, we introduce the idea of adaptive strategy to robust aerodynamic optimization and propose an adaptive stochastic optimization framework. The surrogate model is updated adaptively by increasing training airfoils according to historical optimization results to guarantee the accuracy near the optimal design point, which can greatly reduce the number of training airfoils. The proposed method is applied to a robust aerodynamic shape optimization for drag minimization considering uncertainty of Mach number in transonic region. It can be concluded that the proposed method can obtain better optimal results more efficiently than the traditional robust optimization method and global surrogate model method.     

基于相关滤波的颜色及尺度自适应运动目标跟踪算法

针对相关滤波目标跟踪算法难以适应目标形变、遮挡等复杂场景变化的问题,提出一种颜色及尺度自适应的目标跟踪算法,将颜色空间和尺度自适应运用到跟踪框架中,对视频序列的颜色空间进行分析,然后选取最优跟踪算法通过尺度自适应的方式对目标进行跟踪。选取公开测试集中13段挑战性视频序列与多个前沿运动目标跟踪算法进行对比实验,结果表明:相对于次优的尺度空间跟踪(DSST)算法,平均跟踪精度提高8. 48%,平均重叠精度提高14. 46%,平均中心位置误差减少13. 31像素。在目标发生尺度变化和遮挡等情况下,该算法仍然能够高效地准确跟踪。     

基于梯度有限元的异质材料实体优化设计

针对具有空间分布梯度的异质材料实体的优化设计,建立了两相材料梯度 有限元的概念,利用拉格朗日单元的形函数对体积分数进行插值,在节点邻域内引入设计变 量自适应下界进行梯度控制,利用移动渐近线算法求解优化设计数学模型以使结构满足特定 的功能和目标,以金属夹钳为算例验证了该方法的可行性和鲁棒性。     

Optimal design of planar frames based on structural performance criteria

The aim of this study is to present a new approach, nearer to engineer's point of view, for optimizing the structures, in particular for the planar frames. As a means of improving the overall stability of the structure the objective function chosen to be maximized is the eigenvalues of the buckling modes. The optimization process involves two stages: a preliminary design when a prescribed value for the natural fundamental vibration period is the main constraint and a second stage in which the usual stress, displacement, and side constraints are taken into account. The algorithm used for optimization is based on a classical optimality criteria approach. The steps of the algorithm are illustrated by some examples which demonstrate the effectiveness of the proposed procedure in improving design.     

CAD based shape optimization for gas turbine component design

In order to improve product characteristics, engineering design makes increasing use of Robust Design and Multidisciplinary Design Optimisation. Common to both methodologies is the need to vary the object’s shape and to assess the resulting change in performance, both executed within an automatic loop. This shape change can be realised by modifying the parameter values of a suitably parameterised Computer Aided Design (CAD) model. This paper presents the adopted methodology and the achieved results when performing optimisation of a gas turbine disk. Our approach to hierarchical modelling employing design tables is presented, with methods to ensure satisfactory geometry variation by commercial CAD systems. The conducted studies included stochastic and probabilistic design optimisation. To solve the multi-objective optimisation problem, a Pareto optimum criterion was used. The results demonstrate that CAD centric approach enables significant progress towards automating the entire process while achieving a higher quality product with the reduced susceptibility to manufacturing imperfections.