基于混合整数规划的工厂产品托盘打包及装箱问题研究

目的 针对工厂产品的托盘打包及装箱问题,提出一种优化产品在托盘上的布局以及托盘与产品整体在集装箱中的布局方法,以最大化集装箱的空间利用。方法 在满足现实约束的条件下,以最大化产品装载体积为目标建立混合整数规划模型。考虑问题的复杂性,本文将所研究的问题分解为2个子问题,并建立两阶段装载模型进行求解。第1阶段,建立二维集装箱装载模型,确定多种托盘类型在集装箱底面的平面布局;第2阶段,建立三维托盘装载模型,确定产品在托盘上的立体布局。鉴于精确求解该问题耗时较大,本文针对2个子问题设计两阶段启发式算法求解。为验证模型及算法的有效性,采用2组不同规模大小的算例进行测试。结果 算例结果表明,在小、大2种规模算例中,装载率平均差值分别为0和-0.5%,计算时间相差较大,本文提出的模型及算法在合理的时间内获得了最优解或近似最优解。结论 本研究能够为工厂产品的托盘打包及装箱提供快速高效的解决方案。     

组装结构中的混合边界积分方程模型

本文基于混合应力概念，对结构组装中的荷载传递问题，运用混合边界积分方程方法，建立了比较简的力学模型方程系统，给出了组合方程的离散形式，标定了各个量值的力学含义及数学求解途径，指出了研究结果的意义。     

非典型边界轴向移动绳的行波解及振动抑制

轴向移动绳系统广泛存在于工程设备中，因横向振动问题影响设备的正常运行而备受关注。针对具有非典型边界的轴向移动绳系统，应用行波反射叠加法，拓展了其在任意周期以及在给定初始条件均布简谐激励条件下的振动响应及能量解析解的求解。以边界控制进行振动抑制的方法具有简单、经济等优点。在轴向移动绳系统边界处设置质量-阻尼-弹簧的控制器以及控制力执行器，根据最优阻尼以及反射行波的振动抑制条件设计执行器的控制力，在第一个周期后快速抑制系统的横向振动，通过仿真体现自由和受迫振动时振动抑制的有效性。     

基于IEEE1149．1标准的边界扫描测试技术与方法的研究

边界扫描测试技术是目前一种主流的可测性设计技术,它以特有的结构和检测方法克服了复杂数字电路板测试的技术障碍,能大大提高数字电路的可测试性。本文在深人研究IEEE1149．1边界扫描标准的基础上,根据边界扫描标准定义的测试结构对数字系统的测试方法进行研究,设计出符合IEEE1149．1标准的边界扫描测试系统。主要研究内容如下：详细分析IEEE1149．1标准中定义的测试结构;基于IEEE1149．1标准,提出数字系统边界扫描控制器的设计方案并实现其硬件设计,包括边界扫描控制模块等,并编写上位机软件;最后对数字系统边界扫描测试中的测试方法进行研究。该系统具有极大的应用前景,可以广泛应用于大规模数字集成电路的测试。     

多边形比例边界有限元非线性高效分析方法

比例边界有限元法作为一种高精度的半解析数值求解方法,特别适合于求解无限域与应力奇异性等问题,多边形比例边界单元在模拟裂纹扩展过程、处理局部网格重剖分等方面相较于有限单元法具有明显优势。目前,比例边界有限元法更多关注的是线弹性问题的求解,而非线性比例边界单元的研究则处于起步阶段。该文将高效的隔离非线性有限元法用于比例边界单元的非线性分析,提出了一种高效的隔离非线性比例边界有限元法。该方法认为每个边界线单元覆盖的区域为相互独立的扇形子单元,其形函数以及应变-位移矩阵可通过半解析的弹性解获得;每个扇形区的非线性应变场通过设置非线性应变插值点来表达,引入非线性本构关系即可实现多边形比例边界单元高效非线性分析。多边形比例边界单元的刚度通过集成每个扇形子单元的刚度获取,扇形子单元的刚度可采用高斯积分方案进行求解,其精度保持不变。由于引入了较多的非线性应变插值点,舒尔补矩阵维数较大,该文采用Woodbury近似法对隔离非线性比例边界单元的控制方程进行求解。该方法对大规模非线性问题的计算具有较高的计算效率,数值算例验证了算法的正确性以及高效性,将该方法进行推广,对实际工程分析具有重要意义。     

车内声场的数学模型建立

本文首先利用Ｈｅｌｍｈｏｌｔｚ方程和Ｇｒｅｅｎ定理推导出适合多种边界条件的车内声场边界积分方程，然后利用边界元数值分析技术离散方程，得到已知某一封闭空间边界的振动特性求解其内部声压的边界元数学模型。作为验证，本文还对两个实例进行了试验，结果表明边界元计算值与理论值和试验实测值吻合良好。     

考虑柔性面积需求的动态设施布局方法研究

考虑到实际生产活动中设施形状的不规则性和布局重构过程中设施面积的柔性变化,提出了一种动态设施布局的求解方法。首先,为保证设施布置不超出车间边界、不重叠和位置能够任意互换,引入空间填充曲线表征设施位置和占地面积;然后,在需求可预测的情况下,建立以成本(物料运输费用、设施重构费用和车间租赁费用)最小为目标的动态设施布局模型,并运用模拟退火算法和遗传算法对模型求解,最终得到企业需要合租车间生产多计划期产品时的最优布局策略和最优租赁方案;最后,用算例说明了该方法的可行性与有效性。     

考虑铁路分割线的物流园区功能区布局规划研究

将园区划分为包括出入口在内的11个功能区，采用改进的SLP法，对影响布局的各类因素定量化分析，并且通过分析各功能区之间的物流与非物流关系，确定其密切程度后建立铁路物流园区布局规划模型。该模型以功能区之间总搬运费用最低和综合关系最大为目标函数，设置最小间距约束、边界约束、出入口约束、铁路约束以及长宽约束的约束条件，设计粒子群算法和模拟退火算法相结合的SAPSO法对该模型进行求解，并通过算例验证该方法的合理性和有效性。     

边界积分方程的一种高阶估算技术

基于边界积分方程技术讨论了边界函数未知时的数值估算方法，推导出了均匀各向同性体普遍适用的ＢＩＥＭ公式，给出了积分方程边界值估算法技术的离散格式及数值计算形式，最后分析了矩形及三角形板数值做算例子。     

屏体吸声性能布局对声屏障插入损失的影响

利用边界元法研究声屏障屏体吸声性能布局对道路双侧声屏障插入损失的影响。对于由全反射屏体和全吸声屏体组合而成的声屏障，当两种具有不同吸声性能屏体的面积比相等时，在全吸声和全反射屏体两等分的情况下，屏体布局在多数受声点对于线性声级插入损失基本没有明显区别；在全吸声和全反射屏体四等分的情况下，插入损失最高的布局相对于插入损失最低的布局的改善量最高可达1.5 dB。计算得出，声屏障迎声面上部与底部的屏体吸声性能对声屏障的插入损失影响最大，屏体上部与底部为全吸声的布局总是具有最高的插入损失，而在上部与底部这两部分中，靠近上部屏体的吸声性能对声屏障插入损失改善的影响要比底部屏体更占主要作用。     

三维实体机构空间布局设计

三维实体机构空间布局设计是机构设计中的关键问题之一，本文通过分析、综合实体机构空间布局设计问题的特点，将静态干涉检测法的准确性和扫描体法的连续性结合起来，提出了一种简便、高效的解决方法，该方法通过采用变步长和扫描面的处理方法，提出了计算效率。实例表明所提出的方法能解决运动构件的干涉检测及相应的修形工作 。     

NURBS曲面(实体)扫描体的逼近算法

实现了一种NURBS曲面(实体)扫描而成的扫描体逼近方法。本方法主要通过:①用系列平面的切割,把NURBS曲面(实体)进行降维处理,变成系列平面曲线;②为曲线设置局部标架;③在局部标架下求出每一曲线在每一时刻的极值点而后转换成原曲线的奇异点;④使用fast marching cubes算法删去扫描体内部点,保留扫描体边界上的奇异点;⑤由保留的奇异点通过插值或逼近方式构建边界曲面。本算法能较好地逼近NURBS扫描体,其逼近精度可通过控制切割精度和扫描过程中时间间隔的选取而有效控制。     

Tailoring mechanical and magnetic properties of AlCoCrFeNi high-entropy alloy via phase transformation

Phase constitutions,either changed by alloying or by phase transformation,are the key factors to determine the magnetic and mechanical performances of high-entropy alloys (HEAs).Using the AlCoCrFeNi HEA as a candidate alloy,this paper demonstrates the effect of phase transformation on both the mechanical and magnetic properties in the multi-phase system.With increasing heat treatment temperature,the sigma (σ) and face-centered-cubic (FCC) phases disappeared at 1000 ℃ and 1200 ℃,respectively.Such volume fraction changes ofσ,FCC and body-centered-cubic (BCC) phases have divergent effects on mechanical and magnetic properties.The excellent strength-ductility combination will be achieved as the disappearance of σ phase and formation of FCC phase.As for the magnetic properties,the volume fraction of BCC phase plays a major role in determining its saturation magnetization.When the volume fraction change of BCC phase is not evident,the higher volume fraction of FCC phase will influence its magnetization at 2 T.Our present work might provide insights into analyzing the evolution of both mechanical and magnetic properties of HEAs caused by complex phase transformation.     

An isothermal model of a hybrid Stirling/reverse-Brayton cryocooler

This paper presents a model of a cryogenic refrigerator that integrates a reverse-Brayton lower temperature stage with a 2-piston Stirling upper temperature stage using a rectification system of check valves and buffer volumes. The numerical model extends the isothermal Schmidt analysis of the Stirling cycle by deriving the additional dimensionless governing equations that characterize the recuperative system. Numerical errors are quantified and the results are verified against analytical solutions in the appropriate limits. The model is used to explore the effect of the rectification system’s characteristics on the overall cycle’s behavior. Finally, the model is used to optimize the hybrid system’s design by varying the swept volume ratio and phase angle in order to maximize the refrigeration per unit of heat transfer in the recuperator and regenerator.     

Methodologies for the optimal design of parallel manipulators

In this paper the problem of determining a manipulator design so that its workspace corresponds to a prescribed workspace is considered. Two different strategies, resulting in two different types of optimization problem are considered. The first strategy attempts to obtain a good overall approximation to the prescribed workspace and results in an unconstrained optimization problem. The second strategy entails designing a manipulator so that its workspace fully encloses the prescribed workspace and results in a constrained optimization problem. Two specific formulations of the constrained problem are proposed. The first constrained problem simply aims to fit the manipulator workspace as exactly as possible to the prescribed workspace, while still ensuring that the prescribed workspace is fully enclosed. The second constrained optimization formulation is used to design a manipulator, the workspace of which fully encloses the prescribed workspace, but which is also well‐conditioned throughout the workspace with respect to some performance measure. The particular manipulator used to illustrate and evaluate these formulations is a simple 2‐dof planar parallel manipulator, and the final formulation is also applied to a 3‐dof planar parallel manipulator. Although the manipulators studied here are simple, the objective of this study is to obtain a robust numerical methodology which can be extended to more practical and complex manipulators. Copyright © 2003 John Wiley & Sons, Ltd.     

Kinematic synthesis of a robot with five degrees of freedom

Abstract

This paper studies the geometric design of a robot with five degrees of freedom. According to kinematic synthesis procedure, an industrial robot with five degrees of freedom was used as an example to illustrate the design concept. From the number synthesis point of view, the robot is one freedom less than adequate to perform a general three dimensional motion. The lack of full degree of freedom will restrict the available twist screws for the end‐effector. The unavailable twists of the robot were discovered based on the reciprocal screw system. Singular configurations of the robot were also examined. The dimensional synthesis of a robot is to decide the joint parameters to obtain a good workspace shape and volume. So far, there are no better rules which govern the relations between the joint parameters and the generation of workspace. Under this circumstance, the workspace geometric properties of a robot provide quantitative evaluation of the success of the dimensional synthesis. In this paper, workspace volume and other workspace properties such as the normalized volume index (NV1), volume centroid, and the higher volume moment of inertia are computed. The volume centroid gives the symmetric nature of the workspace, whereas the higher moment reveals the distribution and the compactness of the workspace valume.     

Optimal synthesis for a continuous prescribed dexterity interval of a 3‐dof parallel planar manipulator for different prescribed output workspaces

In this paper, a numerical optimization methodology for synthesizing parallel manipulators for a desired workspace, previously developed by the authors, is extended to determining the design of a three degree of freedom planar parallel manipulator with regard to a specified continuous dexterity capability. In particular the extended method seeks, for a prescribed (2‐D) physically reachable output workspace, a design that yields an output workspace that will not only fully enclose the prescribed physical output workspace with the specified continuous dexterity capability at each point, but will also be optimally conditioned. The performance index chosen corresponds to the condition number of the Jacobian of the manipulator, and the optimum design with respect to the manipulator design variables, is obtained by minimizing the condition number over the enclosed prescribed physical workspace for a continuous range of platform orientations. The proposed optimization methodology produces convincing results, indicating it to be a stable and efficient numerical method for designing planar parallel manipulators for continuous dexterity capability. Copyright © 2006 John Wiley & Sons, Ltd.     

基于人机工程学的老年计算机键盘设计研究

目的应用人机工程学理论研究设计适用于老年人使用的键盘。方法根据手指的生理结构构建手指按键的机构运动模型;利用测量统计得到老年人手的尺寸,应用曲线包络面法得到老年人手指按键的运动轨迹范围,根据该范围得到常用键的区域大小,根据手指和所选键面的相对位置对腕托进行相应设计;根据现有键盘在使用中的不良姿态,对键盘进行总体造型设计;对按键和键盘布局进行设计。结论提出了适合老年人使用的计算机键盘设计方案。     

双相γ+α2钛合金片层承载力的数学模型及预测

为了研究双相γ+α2钛合金晶体中片层组织的承载特性,建立了相应晶体不同取向力学性能的数学模型,并计算了γ相及γ+α2片层组织不同取向的承载力.通过对模型的数值求解,得到γ相和γ+α2片层组织的承载力随不同加载方向的变化规律.计算结果表明:随着α2相体积分数的增加,γ+α2片层组织的最大承载力方向逐渐趋向平行于α2相的(0001)面,临界α2相等价体积分数为λe=30%.这从理论上解释了γ+α2片层组织的最大承载力方向为平行于α2相的(0001)面这一传统观点.这一结论成立的条件为α2相等价体积分数λe>30%.     

双臂机器人协作空间的解算

双臂机器人能极大的拓展机器人的活动能力,在空间科学领域中得到了越来越多的应用.双臂机器人工作空间的形状边界的精确计算在它的优化设计和应用中非常重要.本文针对一种双臂空间机器人的二维地面实验系统,给出了双臂的运动学模型.依据从关节空间到工作空间的运动学映射,采用蒙特卡洛方法分别建立每只操作臂的工作空间.在此基础上针对机器人双臂工作空间的公共区域即协作空间,采用计算机图形学理论中的射线相交方法加以分析计算,得到了协作空间的几何形状.