基于任务-资源图的AGVS循环死锁搜索算法的改进研究

针对AGVS中循环死锁搜索算法研究中存在的不能搜索全部的循环死锁的问题,利用任务-资源图提出一个改进算法.改进算法如下:首先,根据AGV的相对位置关系和执行任务的情况,利用任务-资源图(Task-Resource graph,T-R图)对AGVS进行建模,然后根据循环死锁的T-R图特征,在每一个状态时刻下的T-R图使用图的强连通分支理论搜索循环死锁.当访问完所有状态时刻下的T-R图,也就找到了AGVS中的所有循环死锁.算例验证与理论分析均说明改进算法可以搜索到全部类型的循环死锁,解决了原算法存在的不足.根据改进算法开发的控制规则,可以有效避免新循环死锁的产生.同时指出,对改进算法稍加修改,可以找到AGVS中所有的循环死锁和非循环死锁.     

基于图像视觉伺服的AGV动力学控制

针对具有非完整约束AGV点镇定控制问题,提出一种新的基于图像视觉伺服控制算法.采用眼在手上视觉伺服模型,利用图像视觉伺服原理,基于图像误差设计了AGV视觉控制器,求得AGV广义控制速度;然后根据非完整约束特点的AGV运动学和动力学模型,利用计算力矩法设计了AGV动力学控制器,由广义控制速度计算出AGV控制力矩;从而实现了基于图像误差AGV力矩控制.并利用Matlab和Simulink进行了仿真,仿真结果表明了控制方法的有效性和可行性.最后利用Reinovo型AGV进行了实验,表明该方法具有很好的实用性.     

考虑缓冲区的自动生产单元的无死锁调度策略

在制造系统中,必须防止死锁的发生.本文提出了一种在制造系统(带有有限缓冲区)中搜索最优的无死锁调度的算法.为此首先介绍了死锁问题及其图论表示方法,然后在遗传算法的基础上,运用图论算法来保证无死锁的调度结果.为了保证遗传算法生成的调度策略能够满足所要求的约束,运用图论方法选择无死锁个体,或添加缓冲区,从而在基本保证了系统的主要性能指标的同时,得到系统可行的无死锁调度结果.最后给出了一个运用此方法解决死锁问题的实例.     

仓储式多AGV系统的路径规划研究及仿真

对于自动导引车（Automated Guided Vehicle,AGV）的单机路径规划问题,已存在很多静态算法可以有效求解。但由于AGV间抢占系统资源的相互影响和制约,多AGV的协同作业会出现死锁、碰撞冲突等问题,静态路径规划算法无法满足实时动态作业的系统需求。智能仓储系统中,多AGV动态路径规划的核心问题不再仅是单AGV快速求解最优路径,而在于多AGV的冲突避免或解决,达到整体协调最优。拟采用两种思路解决上诉问题：一种方案是对最有效的静态算法进行改进,并引入动态机制和冲突解决策略以满足作业需求;另一种方案提出一种具备多步前瞻性的主动避障算法,优化路径并提前避开交通拥堵路段,减少冲突可能性和重新寻路代价。实验结果表明两种算法都具有良好的鲁棒性,可有效解决冲突,且后者可持续扩展AGV数量,具有更高的系统效率。     

OpenMP Fortran程序中死锁的静态检测

与BARRIER相关的死锁是导致OpenMP程序失效的重要隐患之一.对该类隐患的静态检测有助于在OpenMP程序运行之前提高其正确性.为了便于检测,将这种死锁分为两类.借助搜索与数据流分析分别按照存在性规则和非一致性规则检测第1类和第2类死锁.扩展了传统的控制流图以表示OpenMP程序.对于每个检测到的死锁,通过回溯记录控制流图中相关的路径,并利用静态分支预测量化其严重程度.基于上述思想,实现了一个OpenMP Fortran程序中死锁的静态检测工具C-Checker.实验表明,该工具能有效地检测OpenMP程序中与BARRIER相关的死锁.     

具有多项式时间复杂性的避免制造系统死锁控制策略

基于系统 Petri 网模型, 研究自动制造系统的避免死锁问题. 对不含中心资源的制造系统, 证明了它只包含安全和死锁两类可达状态. 通过一步向前看的方法, 给出了系统多项式时间复杂性的最佳避免死锁策略. 对一般系统定义了一种辅助 Petri 网. 利用辅助网的最佳避免死锁策略, 提出了综合一般制造系统多项式复杂性的避免死锁策略的方法.     

基于 WebGL 的多AGV物流调度仿真系统的研究与应用

针对K公司汽车总装生产线中多AGV(Automated Guided Vehicle)电量分配不均、路径冲突、AGV利用率低等物流调度问题，为了提高K公司生产线中多AGV物流调度的效率，设计了一种多AGV物流调度仿真系统；利用WebGL(Web Graphics Library) 技术建立了整个生产线场景的三维模型；系统能够自动给AGV分配任务，在AGV执行任务时，将AGV的电池电量和AGV路径规划问题考虑到物流调度系统中；该系统实现了对物流调度系统中AGV运输任务的合理分配，提高了物流调度的效率；经实际应用满足了K公司汽车总装生产线多AGV物流调度工程上的应用。     

OPC技术在AGV控制系统中的应用

通过开放式的OPC技术,利用VC＋＋开发环境实现了OPC客户端,并运用到AGV监控系统中,实现了AGV监控系统和PLC之间的信息交换和互锁控制。     

基于Petri网的柔性制造系统无死锁遗传调度算法

对以最小化加工时间为目标的柔性制造系统无死锁调度问题, 提出了一种遗传调度算法. 算法考虑到同类工件具有预先确定的相同加工路径, 而各工序的处理时间与工件有关. 用Petri网对工序和资源分配进行逻辑建模,利用遗传算法, 采用工序自然编码方式, 基于系统的最佳避免死锁Petri网控制器, 检测染色体的可行性, 修复不可行染色体使其对应的调度满足资源约束和无死锁控制约束, 从而保证算法所利用的所有染色体都对应系统的可行调度. 仿真结果表明了算法的可行性和有效性.     

一种多agent系统中死锁问题的解决策略

多agent系统注重agent之间的相互协作,但是在进行信息传递的过程中不可避免地会出现死锁.文章针对这一问题,结合文献[1]的有关思想,对死锁产生的条件进行了分析,讨论了死锁过程中可能出现的各种情况,利用个体agent的行为的独立性的以及多agent之间的相互依赖关系,采用消息传递和信息存储数据链等技术给出了死锁预防策略以及死锁消除策略,从而有效地对死锁情况进行预防和消除.     

Modeling and deadlock avoidance of automated manufacturing systems with multiple automated guided vehicles.

An automated manufacturing system (AMS) contains a number of versatile machines (or workstations), buffers, an automated material handling system (MHS), and is computer-controlled. An effective and flexible alternative for implementing MHS is to use automated guided vehicle (AGV) system. The deadlock issue in AMS is very important in its operation and has extensively been studied. The deadlock problems were separately treated for parts in production and transportation and many techniques were developed for each problem. However, such treatment does not take the advantage of the flexibility offered by multiple AGVs. In general, it is intractable to obtain maximally permissive control policy for either problem. Instead, this paper investigates these two problems in an integrated way. First we model an AGV system and part processing processes by resource-oriented Petri nets, respectively. Then the two models are integrated by using macro transitions. Based on the combined model, a novel control policy for deadlock avoidance is proposed. It is shown to be maximally permissive with computational complexity of O (n2) where n is the number of machines in AMS if the complexity for controlling the part transportation by AGVs is not considered. Thus, the complexity of deadlock avoidance for the whole system is bounded by the complexity in controlling the AGV system. An illustrative example shows its application and power.     

Deadlock Resolution in Automated Manufacturing Systems With Robots

An automated manufacturing system (AMS) contains a number of versatile machines (or workstations), buffers, and an automated material handling system (MHS). The MHS can be an automated guide vehicle (AGV) system, and/or a system that consists of multiple robots. Deadlock resolution in AMS is an important issue. For the AMS with an AGV system as MHS, the problems of deadlock resolution for part processing process and AGV system as an integrated system has been studied. It is shown that AGVs can serve as both material handling devices and central buffers at the same time to help resolve deadlocks. For AMS with robots as MHS, the existing work treated the robots just as material handling devices and showed that the robots had contribution to deadlock. In this paper, such AMS is modeled by resource-oriented Petri nets. Contrary to the existing work, it is shown that the robots have no contribution to deadlock by adopting such nets to control AMS. More interestingly, they can be used to resolve deadlock by serving as temporary part storage devices. A new deadlock control policy is proposed by treating robots as both material handling devices and buffers. The new policy outperforms the existing ones.     

An integrated model for the design of end-of-aisle order picking system and the determination of unit load sizes of AGVs

In this paper, we deal with an assembly line production system in which an automated guided vehicle (AGV) delivers parts to each workstation of assembly lines from a miniload automated storage/retrieval system (AS/RS). Each assembly production line is characterized by a sequence of workstations linked together for the production of a given type of product. We consider simultaneously the design problem of miniload AS/RS and the problem of determining a unit load size of the AGV. First, a non-linear mathematical model is formulated under a proposed AGV dispatching policy. And then, we determine an appropriate sequence of lines of the vehicle visits. Finally, based on the characteristics of the objective function and feasible region of the decision variables, a heuristic solution procedure is developed to find a near optimal solution. To examine the validity of the model, an example problem is solved.     

Network model and effective evolutionary approach for AGV dispatching in manufacturing system

Automated guided vehicles (AGVs), are the state-of-the-art, and are often used to facilitate automatic storage and retrieval systems (AS/RS). In this paper, we focus on the dispatching of AGVs in a flexible manufacturing system (FMS). A FMS environment requires a flexible and adaptable material handling system. We model an AGV system by using network structure. This network model of an AGV dispatching has simplexes decision variables with considering most AGV problem’s constraints, for example capacity of AGVs, precedence constraints among the processes, deadlock control. Furthermore, these problems can be solved by using a lot of heuristic algorithms as network optimization problems. We are also proposed an effective evolutionary approach for solving a kind of AGV’s problems in which minimizing time required to complete all jobs (i.e. makespan) and minimizing the number of AGVs, simultaneously. For applying an evolutionary approach for this multicriteria case of AGV problem, priority-based encoding method and Interactive Adaptive-weight GA (i-awGA) were proposed. Numerical analyses for case study show the effectiveness of proposed approach. Received: June 2005 / Accepted: December 2005     

AGV scheduling for automated material distribution: a case study

We have studied the scheduling of automated guided vehicles (AGVs) for efficient and uniform material distribution from a truck-dock to machining units of the machine shop in an automotive manufacturing plant. The material distribution problem, being a much simpler special case of the more general material transfer problem, is easily amenable to analysis. We have assessed the number of AGVs required to meet the total material requirements of all the machining units in the shop. Proposing innovative dispatch rules, we have evaluated their performance in simulation by monitoring parameters reflecting efficiency and uniformity of material distribution, both for single AGV and multiple AGV case. In multiple AGV case, we introduce the notion of zones having comparable demands for AGV, and assign one AGV to each zone, so that each AGV can operate largely independently—sharing a minimum path with other AGVs using deadlock avoiding protocols. The results of simulation runs and their implications are discussed.     

柔性制造系统中死锁避免的充要条件第二部分：资源的动态分配规则

本文根据在第一部分中推导出来的描述资源竞争的着色ＲＯＰＮ给出在柔性制造系统中无死锁运行的充分必要条件，从而得出相应的控制规律。它是一种资源动态分配的策略，它决定当一个资源空闲时，是否可以分配给一个任务，可以的话先分配给谁，以保证系统无死锁，并使得资源利用率最大。     

Modeling of AGV networks in flexible manufacturing systems

It is shown that Petri nets are useful tool for modeling of AGV networks in flexible manufacturing systems. In this paper we concentrate on a part of AGV (automated guided vheicle) system that behaves as concurrently and asynchronizingly in FSM.

The main idea of this paper is based on combining of some fundamental parts modeled by colored Petri nets, which are called simply “parts”.

It is also shown that our computer system enables that using the concept of parts, we can construct any AGV model without much effort by operating a mouse, and provides a simulation result.     

多AGV调度系统中的两阶段动态路径规划

为缩短AGV系统的研发周期、降低研发成本,寻求能适应不同地图的通用调度策略以及增强对实际调度任务和故障的鲁棒性,提出了一种两阶段动态路径规划策略．对多AGV调度系统应用两阶段控制策略: 采用动态路径规划进行路径生成,实时对多个AGV同时规划其路径,并通过启发式算法实现路径优化．通过系统仿真证明,该策略很好地提高了AGV调度系统的柔性,是一种能适用于不同地图的通用调度策略．     

Evaluation of automatic guided vehicle systems

This paper presents a methodology for detailed evaluation of autonomous automated guided vehicles systems (AGVS) used for material handling. The methodology includes: stand-alone sub-module evaluation, including comprehensive simulations and statistical analysis of the system's sub-modules, along with hardware validation; quantitative system evaluation for integrated system performance investigation; and structured qualitative analyses for identifying strengths and weaknesses not readily apparent. The defined performance measures include aspects from both multi-robot and AGV fields. The developed methodology provides a systematic way to model, experiment with, analyze, and compare different AGVS control methods. To demonstrate the methodology, it was applied to evaluate a recently developed decentralized AGVS control method.     

AGV路径模糊─变结构滑模─模型参考协调控制

针对自动导向车（ＡＧＶ）的路径跟踪，提出一种新的模型参考－模糊变结构滑模－ＰＩ组合跟踪控制方案。该方案将ＡＧＶ设计成左右轮行走距离跟踪系统，并引进参考模型，组合了模糊控制和变结构滑模控制以及比例加积分（ＰＩ）控制。模糊变结构滑模控制提供了跟踪的快速性和稳定性，ＰＩ控制则消除稳态抖动，提高了稳态精度。仿真及实测结果表明，这种新的设计方案能达到较高的跟踪精度。