考虑多时间约束和机器效率的柔性作业车间调度问题建模及优化

针对传统柔性作业车间调度问题只考虑加工过程的局限性,综合考虑具有工件运输时间、交货期、加工时间以及工件到达时间等多约束,构建了以机器效率最大和最大完工时间最小为目标的调度模型,其中机器效率用每台机器开始加工到结束加工之间的空闲时间和来表示。模型中充分考虑多时间因素并通过工件紧前工序、机器前置工序确定机器的可用时间段和工件的最早开始加工时间。基于遗传算法设计了分段式编码和插入式解码策略,利用S-自适应概率对染色体交叉进行改进,并采用了一种基于最大化机器使用效率的选择策略对机器部分进行变异,另外为保证后代的多样性,提出一种局部种群扩张策略以扩大种群。最后,通过两个不同规模的柔性作业车间调度案例对模型和算法进行测试。实验结果显示所构建的模型适用于该类考虑多时间和机器效率的柔性作业车间调度问题,同时改进算法的表现也优于对比算法。     

基于遗传算法的柔性车间多目标优化调度

针对工件投料时间和机器起用时间不为零的柔性车间多目标优化调度问题,提出了一种改进遗传算法.染色体编码采用机器分配链和工序顺序链的双链结构;用均匀设计法、最短加工时间机器指配法、随机生成法三种方式产生初始种群;由锦标赛方法、最优保存策略和新生策略混合进行选择操作;以传统交叉方式、面向瓶颈机器的交叉方式,以及面向瓶颈工件的...     

基于模糊规则的半导体生产线队列排序算法

为提高芯片的成品率、按期交货率和机器利用率,以及减少平均加工时间,提出了一种工件排序的算法。在该算法中,为提高机器利用率和减少工件平均加工时间,采用了通过排序减少瓶颈机器切换时间的方法;为提高芯片的成品率,引入一时限参数,避免工件在加工过程中因在空气中暴露时间过长而氧化作废;为确保按期交货,在调度过程中运用模糊规则方法确定工件在队列中的具体位置。实验表明,该算法可明显提高产品的成品率,其总体性能优于其他常用算法。     

基于TOC理论的大规模作业车间调度问题研究

针对大规模Job Shop调度问题,提出了一种基于TOC(theory of constraints)的免疫遗传算法。该算法依据TOC理论中瓶颈机约束生产系统性能的思想,利用瓶颈机器的特性,在染色体编码及遗传操作过程中,对瓶颈机与非瓶颈机采用不同的处理方式,以使瓶颈工序得到最优化调度。而非瓶颈工序在满足瓶颈工序的调度方案的基础上进行快速调度,降低大规模作业车间调度问题的复杂度,提高算法的求解效率。为提高算法求解质量,克服遗传算法的随机性及迭代退化问题,将TOC理论中的瓶颈机器拓展至瓶颈工件,提出候选瓶颈工件集及瓶颈工件的定义。通过对瓶颈机接种"瓶颈工件邻域对换"免疫算子,充分利用种群中个体的特征信息,辅助遗传算法的优化过程。仿真结果表明:瓶颈特征的应用以及免疫算子的融入是有效的,免疫遗传算法可以在较短的时间内求得令人满意的解。     

基于极限调度完工时间最小化的机器选择及FJSP求解

为提高柔性作业车间调度问题求解的遗传算法的初始群体质量,通过分析机器选择与调度完工时间的关系,提出一种基于极限调度完工时间(Climit)最小化的机器选择初始化方法。采用机器选择链和工序顺序链双链结构编码,初始化机器选择链时,宏观上采用全局选择和局部选择分别侧重于实现对最大机器负荷和最大工件加工时间指标的优化;微观上采用随机次序取代工件工艺顺序选择工序,在考虑可选机器负荷的基础上进一步比较加工时间选择机器,兼顾最大机器负荷和最大工件加工时间指标的优化。对基准算例机器选择结果进行分析和基于遗传算法求解,验证了所提方法的有效性。     

带机器故障的柔性作业车间动态调度

机器故障是企业在实际生产加工中经常遇到的,文章主要探讨了机器发生故障时的柔性作业车间动态调度问题。依据机器故障发生时,加工机器所处状态,构建了故障机器上剩余工件约束模型,提出了插入重调度和完全重调度的重调度策略,并采用改进遗传算法对其进行求解,最后运用该调度策略对企业生产实际中案例进行计算,发现其完工时间比企业实际加工时间缩短了44.8%,验证所提策略的可行性和有效性。     

基于遗传算法和贪婪算法的作业车间调度

研究了有关Job Shop作业车间调度问题,并分析了与操作顺序有关的工件加工时间和工件到期时间的约束.提出了一种混合遗传算法的调度新算法。运用遗传算法决定各工件的加工时间和每天的使用刀具总数,运用贪婪算法来决定工件在机器上的加工时间和所用的工具。将贪婪算法引入遗传算法的个体解码过程,可提高用遗传算法求解此类问题的效果。     

考虑运输的柔性流水车间多处理器任务调度的混合遗传优化算法

多处理器任务调度在制造业有着较广泛的应用,为了解决实际柔性流水车间环境下的多处理器任务调度优化问题,研究了考虑运输时间和释放时间的多阶段柔性流水车间多处理器任务调度问题,该问题为NP-hard问题,以最小化最大完工时间为目标建立了柔性流水车间多处理器任务调度整数规划模型。为有效求解该问题,首先研究了工件加工机器流生成机制、单工件加工机器流矩阵编码方案和批量工件加工机器流编码方案。进而设计了基于机器空闲随机筛选的工件安排机制,产生该规划的初始解生成方法,以最小化最大完工时间原则进行新解筛选。然后构建基于工件顺序与加工机器流同步交叉的新解更新过程、基于工件顺序与加工机器流同步变异的新解调整过程,并利用迭代贪婪算法完成调整和重建操作,产生全新方案以改善求解质量,最终形成结合迭代贪婪算法的混合遗传融合优化策略。仿真实验利用解的下界得出偏差百分比,分别用遗传算法、迭代贪婪算法和混合遗传融合优化算法对不同规模的问题进行测试,结果表明,混合遗传融合优化算法能够获得较好的近优解。     

基于工件聚类的并行机调度算法及其应用

针对纺织生产广泛存在的带工件释放时间、以最小化总拖期工件数和总拖期时间为目标的大规模并行机调度问题,提出一种基于工件聚类的遗传算法。该算法将求解过程分为工件聚类和工件排序两个阶段。在工件聚类阶段,基于影响并行机调度性能的重要调度特征量,采用改进的模糊C-均值聚类方法将所有待上机工件分为多个聚类;在工件排序阶段,采用基于规则编码的遗传算法,优化各聚类内工件的加工顺序。数值计算结果及实际应用效果表明,所提出的算法适用于求解带工件释放时间的大规模并行机调度问题。     

基于改进非支配排序遗传算法的多目标柔性作业车间调度

采用多目标进化算法解决具有工件释放时间、工件目标差异的柔性作业车间调度问题。依据实际制造系统中存在较多的最大完工时间、平均流经时间、总拖期时间、机器总负荷、瓶颈机器负荷和生产成本性能指标,建立多目标柔性作业车间调度模型。针对柔性作业车间调度问题的特点,设计一种扩展的基于工序的编码及其主动调度的解码机制,以及初始解产生机制和有效的交叉、变异操作;针对非支配排序遗传算法(Non-dominated sorting genetic algorithm II,NSGA-II)在非支配解排序和精英选择策略方面的不足,设计一种改进的非支配排序遗传算法,应用改进的算法求解柔性作业车间调度问题得到一组Pareto解集,并运用层次分析法选出最优妥协解。通过测试基准和模拟实际生产的实例,验证提出算法的可行性和有效性。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.     

Fractional order nonsingular terminal sliding mode control for flexible spacecraft attitude tracking

This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and extern...     

奥氏体不锈钢表面双辉等离子渗锆的动力学

利用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备了一层均匀、致密、呈良好冶金结合的渗锆合金层,并对1 060℃下的渗锆动力学进行了研究。结果表明:随着距锆合金层表面距离的增加,锆元素的含量呈梯度递减,扩散系数逐渐减小,而扩散激活能逐步增大;在1 060℃采用双辉等离子技术渗锆时,渗锆合金层表层的空位密度为2.945×(1012~1013)cm-2,与相同温度下采用常规渗金属工艺相比,提高了1~2个数量级。     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.