基于变复杂度近似模型的汽车安全性和轻量化优化

针对汽车安全性优化过程中考虑冲压效应的计算复杂性特点,采用最优拉丁方实验设计,利用较少样本点数据在传统模型和高精度模型间建立一个差值补偿响应面模型,再通过传统模型和差值补偿响应面模型构造新的实验样本点,在此基础上建立Kriging响应面模型,应用多目标粒子群优化算法对此响应面模型进行优化求解,进行了整车正面碰撞和轻量化多目标优化设计。结果表明,该方法能够在保证响应面精度的前提下,快速收敛于优化解。     

碳纤维增强复合材料加固中心孔钢板综合优化

采用多级优化方法对碳纤维增强复合材料加固中心孔钢板进行优化设计,首先,采用拉丁超立方方法选取试验样本点,利用移动最小二乘法拟合近似代理模型,在代理模型基础上采用自适应响应面优化方法优化基本铺层厚度;然后,结合复合材料制造约束条件,利用Optistruct对铺层顺序进行优化,得到最佳铺层设计方案。经过多级优化设计后,钢板中心孔处应力分布更合理,最大Mises应力减小了56.6%。     

剐齿机床立柱动力学模型修正技术研究

针对机床立柱与床身接触刚度复杂,在有限元建模时边界条件难以确定,会导致机床立柱有限元模态分析结果与模态试验结果存在偏差的问题,通过响应面法与粒子群优化算法组合的方法修正机床立柱的动力学模型。以SKGC-500剐齿机床立柱为研究对象,将立柱与床身之间的导轨连接处理成弹簧阻尼单元,设计变量选择法向刚度和切向刚度。用正交试验设计方法选择有限元分析样本点并拟合二阶多项式响应面模型,建立以固有频率最小二乘法为目标函数,以接触刚度为约束条件的优化模型,用粒子群优化算法对固有频率最小二乘进行优化。结果表明,修正后的立柱动力学模型与实际固有频率有更好的一致性。     

一种径向基代理模型在汽车轮辐翻孔成形中的应用

在材料参数以及模具结构一定的条件下,以汽车轮辐翻孔成形为研究对象,利用Dynaform板料成形软件对轮辐翻孔成形进行数值模拟。通过正交实验设计,建立了一种正交最小二乘法学习的径向基代理模型,对汽车轮辐翻孔成形减薄进行了预测。利用遗传算法对代理模型进行优化,得到了一组翻孔成形最佳工艺参数,从而验证了代理模型的合理性。     

细化Kriging模型在轻轨车轴优化设计中的应用

基于仿真试验,根据低地板轻轨车轴的结构特点和性能指标,将Kriging插值和拉丁超立方抽样试验相结合来构造车轴多目标优化的代理数学模型,并通过多目标遗传算法寻找该代理模型的最优解作为车轴参数的设计依据。为了使所构造的Kriging响应面能准确高效地代表稳健优化目标和约束函数,将Kriging模型在响应面精度检验时的样本点和多目标遗传算法所产生的最优解检验点进行更新,直到达到精度要求为止,从而保证所建立的响应面模型具有较高的全局拟合精度和最优解拟合精度。     

基于加速度频响函数的改进响应面模型修正

为提高模型修正精度,将加速度频响函数引入到改进的响应面模型修正当中.首先分别采用模态参与度准则和有效独立法确定试验最佳激励点和测量点,然后根据待修正参数选取样本点,计算其对应的加速度频响函数,构造初始响应面模型;其次利用三倍方差准则,对预测值进行检验,剔除远离响应面的离群点;再优化初始响应面模型得到最优解作为新的样本点,利用比值型加权方法进行加权,构造加权响应面模型;之后使用改进的响应面模型代替有限元模型,再以频率响应差最小构造目标函数,利用布谷鸟算法求解参数修正值.使用典型的桁架结构模型进行验证,结果表明,改进后的响应面模型计算精度和计算效率都有所提高.     

数控成形磨齿机床身导轨温升与齿面误差补偿

为减小大型数控成形磨齿机床身导轨的热误差、提升齿轮加工精度,研究了导轨温升与齿面加工误差之间的关系及误差补偿方法。以某大型数控成形磨齿机为分析对象,采用多元线性回归—最小二乘法原理,建立了床身导轨温升与砂轮位置偏差的数学补偿模型;结合成形磨削基本原理,建立了砂轮与齿面的接触线方程以及成形磨削斜齿轮的齿面修形模型,最终得到导轨温升与齿面误差的补偿模型,并进行了成形磨齿加工热误差补偿实验。结果表明,该误差模型补偿精度高、实用性强、可靠性好,能够提高齿面加工精度三级以上。所提出的误差补偿模型和方法对促进成形磨齿机加工精度的进一步提升具有重要的指导意义和参考价值。     

基于响应面方法的材料参数反求

板料在冲压过程中处于复杂的各向异性三维弹塑性变形状态,若采用基于传统的单向拉伸试验得到的材料参数进行计算,必然会引入较大的计算误差。提出一种直接从冲压成形过程反求材料参数的方法。该方法将参数反求的问题转换为求试验测量值与仿真计算值之差最小二乘最小的优化问题。试验测量值为冲头的力–位移曲线,而待求的参数包括材料的特性参数和本构参数。采用移动最小二乘响应面法作为优化方法以减少调用正问题计算的次数。由于对冲压成形过程的模拟耗时较多,减少优化迭代的次数意义重大。     

基于并行加点kriging模型的拉延筋优化

为提高kriging代理模型预测精度,基于最大期望提高加点准则,提出一种改进的自适应加点准则和一种并行加点策略。基于kriging模型的预测响应和预测方差,并行加点方法在建模过程中利用粒子群算法并行求解多个加点准则获取多个新样本点更新代理模型,极大提高建模效率。将该方法应用到低维和高维经典非线性函数中,并与单点加点结果相比较,结果表明该方法在保证全局精度情况下,加点次数减少50%以上,并且建模所需总样本数更少。最后以NUMISHEET2002标准考题翼子板成形为研究对象,将该方法应用到板料成形上,建立等效拉延筋阻力和减薄率之间的kriging代理模型,利用并行加点策略快速获取了拉延筋阻力的最优解,消除了翼子板成形中的拉裂缺陷,提高了板料的成形质量。研究表明,改进的自适应加点准则以及提出的并行加点策略可以有效地提高kriging模型的建模效率和建模精度。     

基于智能布点技术的近似模型优化研究及其在冲压成形中的应用

针对基于统计学原理试验设计方法的缺陷,采用一种基于设计变量边界条件以及最优样本信息的智能布点方法,并结合移动最小二乘的响应面近似模型优化方法对非线性问题进行求优。为了验证该方法的有效性,采用该方法对非线性测试函数进行了极值求解。同目前主流的试验设计方法相比,其求解精度以及响应面拟合精度都有一定的提高。将该方法应用于薄板冲压成形体系中拉延筋的优化,得到预期的结果,并成功地用于实际产品成形。     

一种基于增量元模型方法的全局优化算法

针对复杂仿真模型的全局优化问题,提出一种基于增量元模型方法的全局优化算法。首先,分析了现有增量拉丁超立方采样方法新增点数量难以控制以及其数值必须为原采样点数量的整数倍的缺陷,在此基础上利用减法规则思想改进了增量拉丁超立方采样;其次,将改进后的增量拉丁超立方采样与径向基函数的增量更新方法相结合,提出了一种全新的高效全局优化算法;最后,将该算法应用于压力容器的优化设计,计算结果证明了该方法的实用性与工程有效性。     

Optimization of drawbead restraining forces and drawbead design in sheet metal forming process

This paper presents an optimization procedure of drawbead restraining forces in order to improve the sheet metal formability in deep drawing process. A simplified finite element method called inverse approach (IA) has been developed for sheet forming analysis with the consideration of the drawbead restraining forces. This IA is combined with a mathematical programming algorithm to optimize the restraining forces and then to design the drawbeads. The obtained optimization procedure is very efficient due to the simplified assumptions of the IA and the analytical sensitivity analysis. The Square cup of Numisheet’93 and the Renault Twingo dashpot cup are presented to demonstrate the usefulness of the proposed optimization procedure for industrial applications. Verifications of the obtained results have been carried out using a precise incremental commercial code OPTRIS^TM based on explicit dynamic approach to show the effectiveness of our approach.     

Study on one-step simulation for the bending process of extruded profiles

Traditional one-step approaches are either based on the membrane element in which bending effects cannot be considered or based on the simplified shell element in which the initial blank is flat and the curvatures are kept unchanged in the one-step iterative computation. They are not suitable for the bending process of extruded profiles. In order to inspect the formability and possible forming defects in profile bending for preliminary designs quickly and to provide an efficient finite element computation for process analysis, a new one-step approach is presented. In this approach, instead of the traditional simplified shell element, the rotation-free basic shell triangular element is introduced to consider bending effects and make the new one-step approach suited to the simulation of profile bending. On the basis of the presented one-step approach, an in-house program named profile bending simulation-one step (PBS-ONESTEP) has been developed to simulate stretch bending of aluminum extrusions and three-point bending of stainless steel extrusions. The algorithm for initial guess solution of extruded profiles is described. Sliding constraint and the penalty method are adopted to treat contacts for the two numerical examples, respectively. The numerical results of PBS-ONESTEP simulation are compared with those of ABAQUS/EXPLICIT incremental analyses and experiments.     

无线传感网络APIT定位算法的改进

通过对无线传感网络APIT定位算法的研究,知道该算法在定位精确度、定位覆盖率等方面存在较严重的问题。利用移动锚节点在异构传感器网络中的优势,结合TDOA测距算法,并综合考虑整个网络的锚节点部署及优化方法,提出一种APIT定位算法的改进算法。通过仿真实验对改进后的定位算法的性能进行定性分析。改进后的算法在定位精确度、定位覆盖率等方面要明显优于传统定位算法。     

Mould correction for sheet-metal multi-step incremental air-bending forming based on close-loop control and FEM simulation

There exist errors between the manufactured workpieces and the CAD models due to the springback of sheet-metal incremental air-bending forming. To reduce these errors, an off-line closed-loop control iterative algorithm, combined by fast Fourier and wavelet transform, is developed from the displacement adjustment method (DAM), smooth displacement adjustment method (SDAM) and deformation transfer function method (DTFM) for die surface. With this algorithm, the mould surface of sheet-metal incremental air-bending forming could be properly corrected, and the springback errors of the formed workpieces could be effectively reduced. In order to reduce mould cost and labor cost, the springback tests of workpieces forming, needed in the iterative process of closed-loop control system, are substituted by finite element model (FEM) simulation. The above correction algorithm was used in a semiellipse-shape workpiece incremental air-bending forming. Its average errors are +0.74/−0.39 mm. The results show that the mould correction algorithm with Fourier and wavelet transform is reasonable and the means of FEM simulation are effective. It can be taken as a new approach for sheet-metal multi-step incremental air-bending forming and mould design.     

基于遗传算法的非线性控制系统参数优化方法

本文针对非线性控制系统参数优化问题,结合非线性控制系统理论、最优化理论及遗传算法,提出了一种新的仿真优化方法,该方法利用遗传算法来求解非线性控制系统参数优化问题,由于遗传算法是在解空间的多个区域内进行搜索,能以较大的概率跳出局部最优,因此可技巧以整体最优解。仿真结果表明,该方法是一种有效的非线性控制系统参数优化方法。     

Optimization of slider air bearing contours using the combined genetic algorithm-subregion approach

A hybrid optimization approach, the combined genetic algorithm-subregion method, which combines the advantage of the genetic algorithm and the subregion approach, is presented. Using a binary string to represent a selected design space, the combined genetic algorithm-subregion method adopts the genetic algorithm to perform the optimization process. Starting from a pico slider design originally flying at 14 nm, optimized designs were obtained for sliders with target flying heights of 7, 5 and 3.5 nm, respectively. The results show that the combined genetic algorithm-subregion method has good convergence with a substantial reduction of computation time.     

基于微遗传算法的低比转速泵叶轮的优化

提出一种解决加大流量设计对低比转速泵叶轮进行水力设计易出现驼峰,轴功率易产生过载现象的直接优化设计方法,得到综合性能较好的叶轮。其优化设计方法:通过加大流量设计理论设计初始叶轮,将得到的初始叶轮个体与随机个体作为微遗传算法的初始群体中的染色体,并以效率、消除驼峰、气蚀余量最小为分目标函数建立多目标规划作为适应度,进行微遗传操作。最后,结合设计实例进行验证。研究结果表明,将微遗传算法和加大流量设计理论相结合,直接对叶轮进行优化的方法,提升了低比转速泵的综合性能。     

非独立区间变量和随机变量下的单步可靠性计算方法

随机变量和非独立区间变量往往共存,两种变量共存不仅导致出现双层优化问题,而且会降低可靠性的计算效率。为解决双层优化问题和提高可靠性计算效率,基于椭球模型描述的非独立区间变量,利用高维模型表示方法（HDMR）解耦随机变量和非独立区间变量,转换双层优化问题为简单的单步求解问题,基于提出的采样方法,利用二次多项式近似HDMR展式,将隐式的单步求解问题转化为显式问题,提出了一种混合型单步可靠性计算方法。算例结果表明,所提出的单步可靠性计算方法具有较高的计算效率和精度;该方法仅需少量的极限状态函数调用次数,即可获得较高精度的计算结果。     

Solution of dynamic frictional contact problems using nondifferentiable optimization

This article is devoted to the development, implementation and application of variational inequalities (VI) to treat the general elastodynamic contact problem. Unlike existing VI algorithms, which rely on the decomposition of the physical problem into two sub-problems, the current study treats the general VI expressions using one-step approach to identify the candidate contact surface and contact stresses. This is accomplished using nondifferentiable optimization algorithm, through a sequence of mathematical programming problems. The dynamic VI formulations are solved using generalized-α time integration scheme. The selected time integration parameters reduce significantly the spurious high-frequency modes, which persist in the traditional Newmark method. In order to demonstrate the versatility and accuracy of the proposed VI and nondifferentiable optimization algorithm, a number of numerical examples are examined. The results show a significant improvement compared with the existing solution techniques.