Vehicle Travel Time Models for AGV Systems under Various Dispatching Rules

The design and evaluation of AGV-based material handling systems are highly complex because of the randomness and the large number of variables involved. Vehicle travel time is a fundamental parameter for solving various flexible manufacturing system (FMS) design problems. This article presents stochastic vehicle travel time models for AGV-based material handling systems with emphasis on the empty travel times of vehicles. Various vehicle dispatching rules examined here include the nearest vehicle selection rule and the longest idle vehicle selection rule. A simulation experiment is used to evaluate and demonstrate the presented models.     

An object-oriented simulation and extension for tandem AGV systems

An object-oriented simulation modelling environment, AgvTalk, is presented to provide flexible modelling capabilities for the simulation of many alternative automated guided vehicle (AGV) systems. The hierarchical features and modularity of AgvTalk create possibilities for the extension and reuse of simulation object components. The detailed behaviour of each object in the AGV system can also be modelled easily and exactly in AgvTalk because there are no limiting modelling constructs. The modelling capabilities of AgvTalk are demonstrated by designing and simulating a conceptually different configuration AGV system, known as the tandem configuration. For the tandem and conventional AGV systems, the characteristics and design methodology in AgvTalk are described. Simulations between the two systems are compared using AgvTalk in a job shop environment.     

基于混合区域控制模型的多AGV系统调度研究与实现

为降低多AGV系统调度过程的复杂性,提出了一种混合区域控制模型,在模型中采用基于任务等待时间最短原则的SwT调度策略,优化了系统效率和整体运行时间;并提出一种分布式协调控制机制,解决了多AGV在线运行的冲突和死锁问题。最后,搭建了多AGV系统调度的硬件仿真平台,结合具体的加工实例进行了仿真实验,实验结果证明了模型的有效性和可行性。     

PCS颗粒测量技术中软件相关方法的研究

数字相关是PCS颗粒测量技术中的一个关键环节，自相关函数的估计质量直接影响颗粒测量的结果。自相关函数的估计可以通过硬件或软件方法得到。在软件数字相关方法中，利用相关计算时可以得到全部的采样数据这一与硬件相关所不同的特点，能去除采样数据中的均值，并在分析偏差的基础上，采用无偏估计，可有效地提高信噪比，从而获得更好的相关估计值。     

蓝牙无线通讯技术在AGV中的应用

研究了AGV车体与PC控制中心的短距离无线通讯问题，分析了其通讯机理，应用蓝牙模块，80C552微控制器和RS－232接口组成了AGV车载通讯硬件，实现了PC控制中心对AGV的短距离无线控制，实验进一步验证了这一通讯方式的可靠性。     

Dijkstra算法在AGV调度系统中的应用

目前仓储物流配货中,订单的周期短、批量少、批次多,传统的仓储物流模式已很难适应新的需求. 随着自动化仓储物流的不断发展,基于AGV的仓储物流配货技术得到推广与使用. 首先基于仓储物流形式,建立了一个有效仓储空间模型并制订了适于AGV的运行路网,然后根据配单任务需求,给出了AGV运行总距离最短的数学模型,对单任务调用AGV及多任务调用AGV进行分析,运用Dijkstra算法解决了仓储配货系统中AGV与任务的匹配问题.     

工厂AGV的结构设计与控制研究

随着现在科技的进步和发展,工厂对物流自动化程度要求越来越高,从我国汽车装配生产线中的零配件搬运的实际出发,物流的效率是最大的问题,针对这一问题,主要对磁导航AGV的关键模块进行了结构设计,选用PLC作为AGV的控制系统,同时对控制系统的关键模块进行了梯形图编程,很好的体现了AGV小车作为物流自动化的功能,大大的提高了工厂的物流工作效率,减轻了工人的劳动强度。     

基于浅充浅放策略的AGV循环充电装置研究与设计

本文以自动化码头集装箱自动导引运输车(AGV)自动充电系统为研究对象,根据浅充浅放的循环充电原则,分析现有充电系统取电装置存在的问题,在研究国内外各种现存方案的基础上,设计一套原理简单、应用可靠、易于维修保养、更适应于自动化码头AGV工作环境和作业要求的充电系统及取电装置。     

Machine Sharing in Manufacturing Systems: Total Flexibility versus Chaining

In this paper, we compare the operational performance of two machine-sharing configurations: total flexibility and chaining. We show that chaining captures most of the benefits of total flexibility while limiting the number of part types processed on any individual machine to only two. We examine the relative desirability of the two configurations under varying buffer sizes, loading conditions, number of machines, and setup times, as well as for different control policies. For nonzero setups times, we show that chained configurations can outperform fully flexible ones. This particularly is the case when either the number of machines or length of setup times is high. We also find that the effect of the system size on performance diminishes with the number of machines. This means that multiple smaller chains can perform almost as well as a single long one. Our results are consistent with the recent findings of Jordan and Graves (1995), who examined the economic benefits of chaining relative to full flexibility.     

A mathematical programming approach to simultaneous unit-load and fleet-size optimisation in material handling systems design

This paper develops a model for simultaneously determining the optimal performance-based unit-load and fleet sizes for material handling vehicles serving work stations in a manufacturing system. The mathematical programming model maximises the number of units transported by the material handling vehicle during a given production cycle. The optimisation model simultaneously specifies the unit-load and fleet sizes, based on material transportation requirements and system characteristics.     

AGV及其滑模变结构控制器设计

设计了后面两轮驱动,前轮采用万向轮的三轮AGV。在简要介绍其结构和考虑非完整约束基础上．使用矩阵方法分析了AGV转弯问题,得出柔顺运动模式下的状态空间和控制方程。同时,搭建了PC机为上位机,MCS51单片机为下位机的CAN总线无线通讯系统。优化参数下的路径跟踪仿真和实验证明了滑模变结构控制器和无线通讯系统的有效性。     

A cost based evaluation of a zones formation algorithm in tandem AGV systems

In tandem AGV systems, the shop floor is partitioned into a group of non-overlapping zones, where each is served by a single dedicated vehicle. In this paper, a two phase algorithm for partitioning tandem AGV systems is proposed. The proposed algorithm serves a number of objectives including minimizing the total handling cost, minimizing the maximum workload in the system and minimizing the number of between-zones trips. The algorithm is equipped with parameters to enable the user to select one of these objectives or to optimize a combination of them. The performance of the algorithm regarding the objective of minimizing the material handling cost is evaluated by experimental design. The experiment is based on comparing the solutions obtained by the proposed algorithm with best solutions obtained by a ‘rationalized exhaustive enumeration’ procedure for a group of randomly generated problems. The analytical results showed that the proposed algorithm obtains an average of 99.53% efficiency, and that none of the considered factors has a main significant effect on the performance of the algorithm in regards to the objective of minimizing the total material handling cost, however, a few of the interaction effects are significant.     

基于无线传感网络技术的自动化仓库AGV车载通信节点的设计

提出将无线传感网络通信技术用于AGV车载节点的设计,使其能够消除传统无线通信集中控制的弊端,让AGV系统内车辆之间可以自组网络通信,进而实现系统的分布式控制管理,使AGV系统的运作更智能化,提高了系统的工作效率。     

单舵轮AGV小车直线制动横向稳定性分析及优化

单舵轮AGV小车在直线制动时会由于惯性力矩作用而有侧滑趋势,使得小车制动时存在安全隐患。为解决这一问题,以BJ311型单舵轮AGV为原型,创建了小车直线制动时的受力模型,在此基础上分析并推导出小车直线制动时空载与满载时的制动力、地面支撑力、侧偏力和横向摩擦力的公式。将模型的相关参数代入公式中得出制动距离与侧偏力和横向摩擦力的定量关系,结合已得公式可知要控制制动距离的长短。需根据实际作业场地情况调节货物的摆放方式和高度等来控制质心位置,且根据实际情况控制制动速度和加速度的大小。     

定尺剪剪切精度的影响因素和改善措施

介绍了4 300 mm宽厚板定尺剪的结构和组成,分析了影响定尺剪剪切精度的主要原因,并提出了提高定尺剪剪切精度的措施。经过改进后,定尺剪剪切误差控制在1‰以内。     

浆纱机经纱电子式退绕装置及控制系统

本文简述了浆纱机经纱退绕装置的发展过程;着重介绍了自行设计的电子式退绕装置及其自动控制系统的组成和功能,实现了数字化、线性化的经纱恒张力退绕,结构简单、易维修和保养。本设计原理经在ASGA368型浆纱机上的应用,取得了良好的技术和经济效益,是一种非常值得推广的创新设计。     

定宽机加工及装配中的质量控制

介绍了定宽压力机加工过程及装配调试过程的质量控制方法及主要检测指标。通过严格执行质量控制措施,保证了产品质量。     

On the path layout and operation of an AGV system serving an FMS

A major step in the design of an AGV system involves the choice of its layout. Three different AGV layouts serving the same FMS are compared in this paper: a bidirectional line, a bidirectional loop and a unidirectional loop. Different numbers of vehicles are tried by running an ECSL program written for the AGV/FMS simulation. Various velocities and scheduling policies are used which show that bidirectional layouts are more advantageous than unidirectional ones in general, although the latter have been rendered more competitive by the application of a control algorithm for the avoidance of blockages on the track. Scheduling policies, however, are proved to be a key issue. It is therefore necessary to refer any comparison of layouts to a particular scheduling policy. In addition, it was observed that a compromise between factors measuring AGV-layout performance has to be made when assessing layouts, since these factors often follow opposite trends.     

Performance Analysis of Flexible Manufacturing Systems with a Single Discrete Material-Handling Device

We present an analytical model for performance prediction of flexible manufacturing systems (FMSs) with a single discrete material-handling device (MHD). This configuration of FMS is significant for many reasons: it is commonly found in industry, it simplifies material-handling control, it is amenable to analytical modeling, and it forms a building block for more complex systems.Standard queueing models are inadequate to analyze this configuration because of the need to take into consideration many nontrivial issues such as state-dependent routing, interference from the MHD, and the analysis of the MHD. To account for state-dependent routing, we develop an iterative method that is built around mean value analysis. To analyze the MHD interference, we use two queueing network models. In the first, we ignore queueing at the MHD but model the interference from the MHD by inflating the station service times. The second network models the queueing for the MHD and estimates the blocking (inflation) times needed for the first model. By iterating between the two networks, we are able to predict the performance of this configuration of FMS. Our analytical estimates are validated against discrete event simulation and shown to be quite accurate for initial system design.     

定尺剪废料收集系统的结构改造及应用

介绍了莱钢4 300 mm厚板剪切设备的废料收集系统在生产中出现的问题,针对缺陷在结构上进行了改造,达到了满意的效果。