面向防错的混合装配线物流监控

从装配过程的物流控制角度出发,提出了混合装配线主物流和辅助物流的控制策略和方法,给出了详细的数学模型。设计实现了基于装配过程物流控制的防错方法,提供了提高装配质量的手工混合装配线防错控制系统。结合某企业的变速器装配线,给出了系统的应用说明。     

Models of production lines with flexible workstations

This article presents models of production line systems with two flexible workstations. Flexible stations have the capability of switching from one operation to another when they become either blocked or starved. The objective is to determine and compare the production rates of serial and parallel arrangements of the workstations. It is shown that, in general, the serial arrangement achieves higher efficiency. Under some specific assumptions, however, both arrangements have the same production rate. An extension of the analysis of two stations to n stations for the parallel case is also presented.     

A heuristic algorithm for the loading problem in flexible manufacturing systems

The paper considers the loading problem in flexible manufacturing systems (FMSs). This problem involves the assignment to the machine tools of all operations and associated cutting tools required for part types that have been selected to be produced simultaneously. The loading problem is first formulated as a linear mixed 0–1 program with the objective to minimize the greatest workload assigned to each machine. A heuristic procedure is presented in which an assignment of operations to machine tools is obtained by solving a parameterized generalized assignment problem with an objective function that approximates the use of tool slots required by the operations assigned to the machines. The algorithm is coded in FORTRAN and tested on an IBM-compatible personal computer. Computational results are presented for different test problems to demonstrate the efficiency and effectiveness of the suggested procedure.     

一类新的混流装配线排产优化模型

针对混流装配线的负荷均衡化问题,建立了最优化辅助工人数量的一类新的排产优化模型,分析了混流装配线的空间间隔约束和能力约束之间的关系,让明了空间间隔约束是满足工作站能力约束的充分条件.在此基础上给出了有辅助工人参与情况下的空间间隔约束不等式.对一些非线性约束进行了线性化处理,从而可以方便地求解模型.最后,通过仿真实例验让了该方法的可行性和有效性.     

Optimal strip sequencing strategies for flexible manufacturing operations in two and three dimensions

In this paper, optimal strip strategies are developed for a variety of two-dimensional and three-dimensional sequencing problems arising in flexible manufacturing. These strategies are appropriate for CNC drilling operations, NC punching operations, and circuit board population, for example. Seven different metrics are considered.     

面向对象的模块化柔性生产线并行设计研究

针对模块化柔性生产线方案设计系统的复杂性,研究了面向对象的并行设计系统。通过把设计过程分解为对系统若干对象的设计,提出了面向对象的模块化柔性生产线并行设计过程模型。在此基础上建立统一的全局数据模型,开发了箱体类零件柔性生产线并行设计原型系统,以支持加工对象的特征设计、工艺规划、系统配置结构设计、模块化机床、刀具等设计的并行运行,并进行了实例验证。     

A concurrent development tool for flexible assembly systems

Global competition and the rapid pace of technological change now require the almost continual introduction of product upgrades by any manufacturer. Thus, such a manufacturer is likely to market older and newer versions of a product simultaneously, not to mention niche-specific editions of any product upgrade. An increasingly successful response to this product proliferation is the implementation of flexible assembly systems. In the context of a flexible assembly system (FAS), the ability to estimate the impact of various product and process options on the maximal level of system output becomes crucial to managing the ever-changing product mix. This paper presents a tool for such impact estimation that can facilitate concurrent development and engineering. Experience with an actual FAS is the basis for the reported results. The tool is a specialized combination of discreteevent computer simulation, experimental design, and regression analysis. Application of the tool assumes FAS use with a cellular manufacturing philosophy. Thus, uncluttered process flow for a family of products in the sense of group technology places the focus on potential bottlenecks. The new tool here models the impact of process and product options on bottleneck and, hence, FAS behavior.Working paper presented at the Third ORSA/TIMS Special Interest Conference on Flexible Manufacturing Systems, August 14–16, 1989, M.I.T., Cambridge, Massachusetts.     

基于混合遗传算法的混合装配线排序问题研究

为使混合装配线有效运作,研究了混合装配线的生产排序问题。以装配线上各种零部件消耗速率均匀化和最小生产循环周期最短为优化目标,描述了多目标排序问题,并建立了优化模型。针对基本遗传算法在求解排序问题时的早熟收敛问题,提出一种改进混合遗传算法。该算法借助模拟退火算法思想对适应度尺度进行调整,使遗传进化初期削弱种群中个体适应度差异,而在遗传进化后期强化种群中个体适应度差异,以提高对最优解的搜索能力。同时,根据个体适应度自动调整遗传操作参数,既保存了种群中的优良个体,又不失个体的多样性。最后通过案例分析验证了算法的有效性。     

用于机器人螺钉柔性装配的夹持器

从机器人螺钉柔性装配位姿调整策略的需要出发,简要介绍了机器人末端适从方式,提出了基于刚度矩阵的适从表达方案,设计并制作出具有良好适从特性的螺钉柔顺夹持器,实验结果表明,该夹持器所具有的较宽位姿适从范围为机器人螺钉柔性装配的实施打下了良好基础.     

A genetic-algorithm-based optimization model for scheduling flexible assembly lines

In this paper, a scheduling problem in the flexible assembly line (FAL) is investigated. The mathematical model for this problem is presented with the objectives of minimizing the weighted sum of tardiness and earliness penalties and balancing the production flow of the FAL, which considers flexible operation assignments. A bi-level genetic algorithm is developed to solve the scheduling problem. In this algorithm, a new chromosome representation is presented to tackle the operation assignment by assigning one operation to multiple machines as well as assigning multiple operations to one machine. Furthermore, a heuristic initialization process and modified genetic operators are proposed. The proposed optimization algorithm is validated using two sets of real production data. Experimental results demonstrate that the proposed optimization model can solve the scheduling problem effectively.     

Optimization of line configuration and balancing for flexible machining lines

Line configuration and balancing is to select the type of line and allot a given set of operations as well as machines to a sequence of workstations to realize high-efficiency production. Most of the current researches for machining line configuration and balancing problems are related to dedicated transfer lines with dedicated machine workstations. With growing trends towards great product variety and fluctuations in market demand, dedicated transfer lines are being replaced with flexible machining line composed of identical CNC machines. This paper deals with the line configuration and balancing problem for flexible machining lines. The objective is to assign operations to workstations and find the sequence of execution, specify the number of machines in each workstation while minimizing the line cycle time and total number of machines. This problem is subject to precedence, clustering, accessibility and capacity constraints among the features, operations, setups and workstations. The mathematical model and heuristic algorithm based on feature group strategy and polychromatic sets theory are presented to find an optimal solution. The feature group strategy and polychromatic sets theory are used to establish constraint model. A heuristic operations sequencing and assignment algorithm is given. An industrial case study is carried out, and multiple optimal solutions in different line configurations are obtained. The case studying results show that the solutions with shorter cycle time and higher line balancing rate demonstrate the feasibility and effectiveness of the proposed algorithm. This research proposes a heuristic line configuration and balancing algorithm based on feature group strategy and polychromatic sets theory which is able to provide better solutions while achieving an improvement in computing time.     

面向机翼柔性制孔的多层次数控程序结构

为实现飞机自动化柔性制孔技术,针对机翼的结构及其装配特点,研究了机翼柔性制孔工艺,提出了柔性制孔过程的二次定位方法,并根据该工艺划分了多层次的数控程序结构。该结构包括三个层次,分别是整体结构层、单肋加工层与单孔制孔层。整体结构层表达数控程序的整体结构,包含加工过程中各个基本单元的设置与单肋加工过程的制孔顺序;单肋加工层不但对肋骨加工单元的加工过程进行编制,而且对肋骨中的制孔路径进行规划;单孔制孔层以子循环的形式完成柔性制孔过程中的最基本环节。为快速生成该结构的数控程序,开发了面向机翼柔性制孔的离线编程系统。以某型飞机机翼为例,通过与传统编程方法的对比,分析了该程序结构的编程效率与可维护性,验证了系统的有效性。     

A line-balancing strategy for designing flexible assembly systems

We present a rough-cut analysis tool that quickly determines a few potential cost-effective designs at the initial design stage of flexible assembly systems (FASs) prior to a detailed analysis such as simulation. It uses quantitative methods for selecting and configuring the components of an FAS suitable for medium to high volumes of several similar products. The system is organized as a series of assembly stations linked with an automated material-handling system moving parts in a unidirectional flow. Each station consists of a single machine or of identical parallel machines. The methods exploit the ability of flexible hardware to switch almost instantaneously from product to product. Our approach is particularly suitable where the product mix is expected to be stable, since we combine the hardware-configuration phase with the task-allocation phase.For the required volume of products, we use integer programming to select the number of stations and the number of machines at each station and to allocate tasks to stations. We use queueing network analysis, which takes into account the mean and variance of processing times among different products to determine the necessary capacity of the material-handling system. We iterate between the two analyses to find the combined solution with the lowest costs. Work-in-process costs are also included in the analysis. Computational results are presented.     

基于智能元件的柔性夹具设计新方法（2）

为实现柔性夹具设计过程中的元件感知设计环境,辅助工艺员选件、尺寸驱动与自主装配,提出基于智能夹具元件的设计推理方法。在夹具布局设计完成的基础上生成工件本体,以工件本体模型推理智能柔性夹具元件选择,给出基础元件、支撑元件、定位元件与夹持元件的选件规则。利用工件功能特征与元件功能特征、元件之间的配合特征位置关系驱动智能元件的尺寸规格。利用预定义的装配模式推理元件配合关系,并实现元件之间的自动装配。通过开发柔性夹具设计系统,验证了智能夹具元件在设计过程中的有效性。     

求解柔性作业车间调度的遗传算法综述

柔性作业车间调度(FJSP)是一类具有广泛应用背景的调度问题,作为求解FJSP最受欢迎的算法之一,遗传算法引起了广泛关注。针对求解FJSP的遗传算法,特别是5类主要染色体编码方法以及相关的交叉和变异算子进行全面综述,并从编码可行性、编码空间与解空间的映射关系、染色体存储空间、解码复杂性、编码完备性、遗传操作复杂性和遗传操作多样性7个维度综合评价了5类编码方法。结果表明,MSOS-I编码是遗传算法求解FJSP较好的染色体编码方法,其染色体结构简单,并可选用较多类型的交叉和变异算子。     

Optimal load balancing leveling method for multi-leg flexible platforms

The working platforms supported with multiple extensible legs must be leveled before they come into operation.Although the supporting stiffness and reliability of the platform are improved with the increasing number of the supporting legs,the increased overdetermination of the multi-leg platform systems leads to leveling coupling problem among legs and virtual leg problem in which some of the supporting legs bear zero or quasi zero loads.These problems make it quite complex and time consuming to level such a multi-leg platform.Based on rigid body kinematics,an approximate equation is formulated to rapidly calculate the leg extension for leveling a rigid platform,then a proportional speed control strategy is proposed to reduce the unexpected platform distortion and leveling coupling between supporting legs.Taking both the load coupling between supporting legs and the elastic flexibility of the working platform into consideration,an optimal balancing legs’ loads(OBLL) model is firstly put forward to deal with the traditional virtual leg problem.By taking advantage of the concept of supporting stiffness matrix,a coupling extension method(CEM) is developed to solve this OBLL problem for multi-leg flexible platform.At the end,with the concept of supporting stiffness matrix and static transmissibility matrix,an optimal load balancing leveling method is proposed to achieve geometric leveling and legs’ loads balancing simultaneously.Three numerical examples are given out to illustrate the performance of proposed methods.This paper proposes a method which can effectively quantify all of the legs’ extension at the same time,achieve geometric leveling and legs’ loads balancing simultaneously.By using the proposed methods,the stability,precision and efficiency of auto-leveling control process can be improved.     

飞机立柱式柔性工装定位误差分析与精度保障

为保障柔性工装各组成立柱式三坐标定位单元的定位精度0.05 mm的设计要求,实现基于协调孔的精确装配定位,在某机型四个前缘襟翼部件柔性装配过程中,根据柔性工装的定位特点对柔性工装定位精度影响因素进行了综合分析.在所建立的工装坐标系下应用激光跟踪仪测量立柱定位单元的定位精度,基于滚珠丝杠传动系统的轴向定位误差与导程误差、导轨导向传动系统的安装定向误差,建立柔性工装立柱定位单元单轴运动的定位误差模型,对综合定位误差进行计算,并提出了定位精度保障的实验方案.实验表明,经误差补偿后,柔性工装立柱定位单元的定位精度完全能够满足工程中对飞机部件定位精度的要求.     

基于人工神经网络的某空间反射镜柔性支撑结构优化设计与分析

空间反射镜的支撑结构决定了反射镜的性能。通过有限元分析来优化支撑结构参数需要很大计算量,而且无法找到最优解。为了缩短设计周期,提出用人工神经网络来模拟反射镜组件输出特性和支撑结构参数间的非线性关系,并用MATLAB编制程序实现神经网络的建立和泛化,最终找到使反射镜输出特性最优的支撑结构参数。该方法不但能找到多变量优化的最优解,而且计算表明用神经网络泛化得到结果和有限元分析计算得到的结果相差在5%以内,精确度足以满足工程应用要求。     

飞机大部件调姿机构柔性多体动力学建模与仿真

为保证飞机大部件调姿的质量与可靠性,构建了调姿机构的动力学模型,模拟了整个调姿过程。根据调姿机构自身特点将三坐标定位器的支撑杆视为柔性体,综合运用拉格朗日方程、虚功原理与拉格朗日乘子法,建立了调姿机构的柔性多体动力学模型;经数值求解得到调姿过程中飞机部件和定位器的受力情况,通过仿真算例验证了所建立的动力学模型的正确性和有效性。该动力学模型可为实现调姿过程的自动控制提供有力的依据。     

并行生产线的批量分割和调度优化

研究了一类并行生产线上生产调度和批量分割的同时优化问题。给出了产品在生产线上连续加工时产品批量的完工时间计算公式,并证明了该公式的正确性。考虑相邻批次在生产线上加工会产生重叠,给出了产品批量开工时间的一个下界。证明了批量连续发交时保证缓冲区总是可用的充分条件,并在此基础上提出了一个求解批量开工时间的迭代算法,该算法计算复杂度与批量大小无关。最后通过建立的批次发交模型和提出的批量分割启发算法,构造了一种基于遗传进化的启发式方法以求解该类问题。计算实验表明,该方法通过批量分割可以有效地平衡生产线上的负荷。