FMS中资源共享导致的死锁状态及其避免方法

针对FMS中多种操作对有限资源的竞争会导致死锁状态，采用Petrinet分析技术对其进行了研究。建立了FMS的PPN模型，并在此基础上给出了直接死锁和潜在死锁的定义；引入了死锁状态方程的概念并给出了其构造方法；描述了死锁状态和资源分布之间的内在联系，并提出了一种死锁避免方法。实例表明该方法能够简单有效地避免死锁的产生，并允许资源的最大利用。     

自动化仓库输送过程调度问题研究

自动化仓库中输送系统的工作过程具有典型的离散事件特征。本语文基于面向对象着色Ｐｅｔｒｉ网模型，讨论了该过程的死锁分析问题，并给出了死锁避免的最大允许反馈控制策略。     

复杂并行共享资源与系统死锁

研究了制造过程共享资源引起的死锁问题。提出了并行资源死锁结构的概念。对于包含该结构的系统，给出了Petri网模型具有可能死锁的充要条件。基于资源向量的概念，提出了一个简单方法，用于判断系统是否具有可能的死锁。针对包含死锁结构的系统，提出了系统Petri网无死锁的设计方法，举例说明了这种方法的应用。     

自动导引车系统避碰及环路死锁控制方法

为了避免单向导引路径网络中各自动导引车间发生碰撞及系统死锁,以基于单向导引路径网络的自动导引车系统为研究对象,提出一种避免自动导引车间碰撞的避碰方法。针对基于单向导引路径的自动导引车系统特点,建立了基于有向图的自动导引车系统运行状态模型,基于该模型提出一种环路死锁搜索方法。定义了包括单环路和多环路死锁临界状态的环路死锁临界状态概念,针对两种环路死锁临界状态,设计了对应的死锁控制策略。通过仿真证明了所提方法的有效性。     

多载量AGV系统防死锁路口通行顺序优化及避碰

多载量自动导引车(AGV)具有更高的单车运输能力和更强的配送作业柔性,然而其长度不断变化的特点也加大了交通管控的难度。为保证生产线多种物料准时配送,研究了多载量AGV系统的交通管控问题。首先分析了与单载量AGV差异较大的两种运动冲突：针对多载量AGV变长特性,设计了一种变长度AGV路径空间冲突避免方法;针对交叉路口冲突,考虑到多载量AGV变长特性对阻塞环路死锁的影响,提出一种带防死锁策略的交叉路口通行顺序优化方法。根据AGV紧迫度和交通负荷均衡度构建了综合竞标价模型,并对获标AGV即将进入的目标路径段的阻塞环路进行死锁预测与避免。仿真实验结果表明,所提方法可保证任务紧迫度高的AGV优先通过,降低路口相关路径段的交通拥堵,并避免高密度AGV系统的环路死锁,从而提高生产线物料配送的任务准时率。     

基于时间窗的自动导引车无碰撞路径规划

针对柔性制造系统中自动导引车的无碰撞路径规划问题,结合预先规划算法和实时规划算法的优点,提出基于先验决策的自动导引车无碰撞路径规划方法.将Dijkstra算法和时间窗原理相结合,顺序规划各个自动导引车的路径.在已规划自动导引车路径的基础上,运用基于Dijkstra的算法继续规划下一自动导引车,实现自动导引车的无碰撞路径规划.该算法能有效避免死锁及碰撞,并保证最优化路径,能快速响应新的任务,在动态环境下具有较好的柔性.结合实例说明了该算法的实现过程,并证明了该方法具有较好的鲁棒性和柔性,同时能提高系统效率.     

一种基于Petri网和AGA算法的测试系统死锁预防策略

在自动测试系统中,很多任务需要并行测试.测试过程比串行测试复杂,较容易出现死锁现象,因此提出一种基于Petri网和自适应遗传算法(adaptive genetic algorithm)的死锁预防策略.在该策略中,首先为自动测试系统建立一个Petri网模型,然后将Petri网的状态方程作为约束条件,最后求出模型的发射序列即系统中无死锁的任务调度路径.Petri网的发射序列求解一直是NP问题,针对这种情况,引入自适应遗传算法对可行解空间进行全面的搜索,可得到所有无死锁的路径.最后,通过雷达接收机的并行测试例子,和启发式算法搜索进行对比,进一步体现了该死锁预防策略的优越性.     

自动小车存取系统中轨道导引小车环路死锁控制的研究

为防止自动小车存取系统中轨道导引小车环路死锁现象,提出了一种基于Petri网和有向图的死锁控制方法.该方法首先应用有色赋时Petri网建立了自动小车存取系统的动态模型,并结合有向图工具,阐述了导致环路死锁的原因.在此基础上,针对单一轨道双向运行的轨道导引系统,探讨了其环路死锁的主要表现形式,给出了轨道导引小车无死锁运行的充要条件,并提出了包含临界状态在内的死锁避免控制策略.最后,结合实例说明了环路死锁控制的有效性.     

自动制造系统的一种死锁避免策略

基于Petri网的结构分析理论，提出了自动制造系统Petri网模型的一种死锁控制方法，在这种策略的控制下，避免了系统中死锁的产生，从而许多制造系统的Petri网模型具有活性，提出了一种保证所有严格极小信标至少含有一个托肯的方法，对冗余严格极小信标的研究，提高了Petri网复杂自动制造系统的建模能力。结果表明，在设计无死锁的Petri网格型时，不是所有的严格极小信标都要考虑，从而简化了设计结果和控制算法。     

FMS运控软件调试环境中的死锁检测方法

ＦＭＳ中存在死现象是理想的，此时系统至少存在一个等待环，环中工件处于互相等待彼此所占有资源的状态。对于一个ＦＭＳ控制软件，如果不具死锁的预测和回避方法，在实际运行过程中就会因可能出现的死锁现象而发生故障，在建立ＦＭＳ运控系统调试环境时，本文旨于确认被测ＦＭＳ运控软件的死锁预测和回避功能。在被测系统Ｐｅｔｒｉ网模型的基础上，根据选定的调度策略确定所有被占用资源上工件的目标库所集，以检验系统中是否在死     

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...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

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。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.