基于不可微问题优化的四面体网格光顺算法

提出一种基于不可微问题优化的四面体网格光顺算法。针对四面体网格光顺的最小最大约束优化问题,应用一类不可微优化问题的有效解法,提出与不可微目标函数等价的可微目标函数,进一步转化为无约束极小优化问题,进而调用现有的优化程序库进行网格优化。该算法实现了多点并发优化技术,能够有效地实现四面体网格的质量优化,特别是能够有效地解决非孤立劣质单元优化问题。算例表明,该算法计算效率高,且易于实现,能够优化得到较高质量的四面体网格。     

综合评价指标约简算法综述

针对综合评价问题构建指标体系时求全和求精这一对矛盾体的寻优问题，研究了现有2大类7种指标约简算法：主成分分析和因子分析法、极小广义方差法、极大不相关法、灰色关联分析法、基于差别矩阵的指标约简算法、基于信息熵的指标约简算法、基于粒计算的指标约简算法。研究了这些算法的原理和各自特点及应用场合，为综合评价指标约简方法选择提供支撑。     

基于NGA的C-Bézier曲线降多阶逼近

针对C-Bézier曲线的降阶逼近问题,提出了一种将1条n次C-Bézier曲线降阶为1条m(m相似文献   

球面四杆机构近似函数综合的自适应方法

给出了球面运动刚体上具有二次鞍点意义的近似圆点的定义,提出了球面曲线的自适应圆弧拟合方法,把实现给定函数关系的球面机构综合转化为球面上曲线的自适应圆弧拟合逼近问题,建立了球面运动近似函数综合的数学模型和鞍点规划求解方法,由此在理论上阐明了球面四杆机构近似运动综合问题存在最优近似解和收敛性算法。为了克服初始值选取和获得全局最优解等困难,采用了遗传算法的思想,算例表明可行有效。     

具有上界约束的挠性转子最优平衡质量计算

将具有平衡质量上界约束的挠性转子动平衡问题表示成非线性规划问题并分析其解的最优性条件,在此基础上提出转子最大残余振动极小化的迭代重加权阻尼最小二乘算法。该算法通过极小化一个二次目标函数序列得到最大残余振动极小化意义下满足上界约束条件的最优平衡质量。通过计算示例验证了该方法的有效性。     

改进的BP算法在多目标识别中的应用

为了实现对多目标的识别,提出了一种改进的BP算法。采用在步长函数中加入变动量因子,即当连续两次迭代其梯度方向相同时,步长加倍;当连续两次迭代其梯度方向相反时,步长减半。由于步长在迭代过程中自适应进行调整,使误差函数E在超曲面上的不同方向按照步长向极小点逼近,实现了对目标函数的优化。给出了在目标函数最优时的BP网络对三种飞机测试集的识别结果,其收敛速度比传统BP算法快4倍以上,表明该方法能够有效地用于多目标的识别。     

基于神经网络的冗余度机器人动态最优化控制

进行了冗余度机器人动态最优化控制的研究,由于局部优化方法有一定的局限性,研究中采用了全局优化方法,基于全局优化的思想,提出了一种冗余度机器人的动态优化控制算法,由于控制算法在数值求解时的困难性,在算法中应用了神经网络,用其来逼近复杂的非线性函数,使问题求解得以简化,通过仿真验证,此控制算法能够获得良好的动态性能,运算速度快,具有工程应用的可行性。     

基于极大极小代数法的最优调度方法

阐述了将制造系统生产排产的实现算法与优化调度的算法结合起来的一种方法.提出极大极小代数法,建立与工艺路线矩阵和设备-零件加工时间矩阵相容的自动排产机制,从中产生性能函数,作为优化调度的目标函数.优化调度的算法是改进的模拟退火法,通过设立改进解变量,保留已经出现过的最优解,同时利用随机生成的迭代解跳出局部最优,最终结果收敛于全局最优或近似全局最优.并以算例说明.     

平面六杆高级机构高阶函数发生器的综合

本文提出了分组迭代逼近线性叠加最优综合法用于解决平面高级机构的高阶运动参数函数发生器的综合。将机构分析过程与机构综合过程有机地结合起来,建立了四边形和五边形环路方程及求解方法,成功地求解了平面高级机构函数发生器的综合问题。     

基于改进遗传算法的函数优化及其性能分析

工程应用中,常涉及到最优化问题.对很多问题进行数学建模后,都可以抽象为一个数值函数的优化问题.实践表明,遗传算法求解最优化问题的计算效率很高.提出了一种对简单遗传算法的编码方式、选择算子、交叉算子及变异算子都进行改进的算法,仿真试验表明,改进算法的函数优化计算在搜索效率和收敛速度方面都有很大提高.     

A robust optimization model for p-median problem with uncertain edge lengths

In this paper, we propose a p-median problem with uncertain edge lengths where uncertainty is characterized by given intervals. The uncertainty in edge lengths may appear in transportation costs or travel times along the edges in any network location problem. Minimax regret approach is a promising tool to cope with uncertainty in network location problems. However, minimax regret algorithms normally suffer from complexity, and they are time consuming. We propose a robust optimization approach to obtain the robust linear counterpart for the same class of the nominal p-median problem. The performance of the proposed model is compared with minimax regret approach through a simple but illustrative example, and results are discussed in more details.     

Semidefinite programming for Chebyshev fitting of spatial straight line with applications to cutter location planning and tolerance evaluation

This paper presents a novel model for fitting of spatial straight line based on Chebyshev norm. The problem is firstly formulated as a minimax problem, and then reformulated as a semidefinite programming (SDP) problem, which could be solved by many interior-point algorithms. The application of the proposed approach to two problems arising from manufacturing engineering, i.e. planning of the initial location of cylindrical cutter for flank milling and evaluation of the spatial straightness error, is discussed. Examples and numerical simulations illustrate the efficiency of the novel model.     

SQP algorithms in balancing rotating machinery

Increased running speeds and the requirement for rotating machinery to operate within specified levels of vibration mean that the control of machinery vibration is essential in today's industry. In this paper, the flexible rotor balancing problem based on the influence coefficient method and holospectrum technique is formulated as a minimax optimisation problem. This formulation can solve the minimax high-speed rotating machinery's balancing problem under practical balancing constraints effectively while ensuring the balancing machinery runs up safely. Sequential Quadratic Programming (SQP) method is employed to solve the minimax balancing problem. An experimental and a real world balancing example are given to demonstrate the effect of this formulation. The performance of SQP is compared with that of other established approaches; some conclusions are derived.     

双材料结构非概率可靠性拓扑优化设计

利用凸模型描述和非概率可靠性的量化定义,研究存在材料属性、几何及荷载不确定性的双材料结构拓扑优化问题。基于扩展的相对密度惩罚方法,建立优化模型为给定材料体积约束下,同时满足可靠性要求的连续型极小极大优化问题,以寻找两种不同实心材料的最优联合材料分布布局。采用序列近似规划策略,结合不确定参数直接迭代公式和移动渐近线方法来求解该极小极大优化问题。该方法可把原问题转化为一系列近似的确定性优化问题,从而极大减少了计算量。数值研究表明,存在的不确定性可能对双材料结构的最优联合布局产生较大影响,优化模型和数值算法为双材料结构拓扑设计提供了一个有效途径。     

Technology of solving multi-objective problems of control of systems with distributed parameters

A constructive technology of multi-objective optimization of control of distributed parameter plants is proposed. The technology is based on a single-criterion version in the form of the minimax convolution of normalized performance criteria. The approach under development is based on the transition to an equivalent form of the variational problem with constraints, with the problem solution being a priori Pareto-effective. Further procedures of preliminary parameterization of control actions and subsequent reduction to a special problem of semi-infinite programming make it possible to find the sought extremals with the use of their Chebyshev properties and fundamental laws of the subject domain. An example of multi-objective optimization of operation modes of an engineering thermophysics object is presented, which is of independent interest.     

A Computational Synthesis Approach of Mechanical Conceptual Design Based on Graph Theory and Polynomial Operation

The design synthesis is the key issue in the mechanical conceptual design to generate the design candidates that meet the design requirements. This paper devotes to propose a novel and computable synthesis approach of mechanisms based on graph theory and polynomial operation. The graph framework of the synthesis approach is built firstly, and it involves:(1) the kinematic function units extracted from mechanisms;(2) the kinematic link graph that transforms the synthesis problem from mechanical domain into graph domain;(3) two graph representations, i.e., walk representation and path representation, of design candidates;(4) a weighted matrix theorem that transforms the synthesis process into polynomial operation. Then, the formulas and algorithm to the polynomial operation are presented. Based on them, the computational flowchart to the synthesis approach is summarized. A design example is used to validate and illustrate the synthesis approach in detail. The proposed synthesis approach is not only supportive to enumerate the design candidates to the conceptual design of a mechanical system exhaustively and automatically, but also helpful to make that enumeration process computable.     

Design of adaptive backstepping congestion controller for TCP networks with UDP flows based on minimax

The congestion control problem of TCP network systems with user datagram protocol (UDP) flows is investigated in this paper. A nonlinear TCP network model with strict-feedback structure is first established. The unknown UDP flow is regarded as the external disturbance, and the maximum UDP flow is calculated by using the minimax approach. And then, a congestion control algorithm is proposed by using the adaptive backstepping approach. Meanwhile, the adaptive law is employed to estimate the unknown link capacity. The design of the adaptive law is to introduce a parameter mapping mechanism to limit the parameter identification range to a specified interval, thereby improving the estimation efficiency of the parameters. Furthermore, a state-feedback congestion controller is presented to make sure that the output of the system tracks the desired queue. The simulation results show the superiority and feasibility of the proposed method.     

A new approach to the synthesis of 4-bar function generatorsNeue methoden für die synthese viergliedriger funktionsgeneratoren

In the present work a new approach to the synthesis of 4-bar function generators has been presented. Using this graphical method quick and at the same time sufficiently accurate synthesis is possible in a large number of cases. The method is based on the principle of coordinating two positions and the corresponding velocities of the input and the output links. Thus four conditions are satisfied and better accuracy than that with three point synthesis may be expected. Positions of the proper accuracy points have been discussed and some guidance to the selection of the initial data has been presented in this paper. One problem has been solved as an example.     

冗余驱动Tricept并联机构的驱动优化

对冗余驱动3自由度Tricept并联机构的逆运动学和逆动力学进行分析,基于牛顿—欧拉法建立机构的逆动力学方程。针对冗余驱动方式下机构主动关节之间驱动力分配不唯一的特点,研究机构按预期轨迹运动时的驱动优化问题,提出最小化驱动器最大瞬时驱动功率和最大瞬时驱动力的优化方法。结合实例分析机构驱动力2范数优化、最小化最大驱动力优化和最小化最大驱动功率优化的效果,并与非冗余驱动方式进行对比。分析显示,冗余驱动能够较显著地降低驱动器的瞬时负载和瞬时输出功率,并可结合驱动力2范数优化、最小化最大驱动力以及最小化最大驱动功率的优化效果分析,选取适当的驱动方式以实现驱动器瞬时负载与瞬时输出功率的均衡与优化。