基于机器视觉的微小型零件精密装配

基于机器视觉的精密装配是实现微小型零件自动组装的重要方法.所研制的基于机器视觉的自动装配系统解决了某小型产品装配中的关键问题,其中包括待装配的零件尺寸相差大、形状和特征多样、表面质量差别较大、需要同时保证组装的位置精度和形位公差等.采用Canny边缘提取、圆的最小二乘拟合、轮廓提取、质心主轴计算、图像拼接等方法实现了待装配零件的识别定位,通过设备坐标系统的转换保证了小型零件的精确装配.实验结果表明装配精度小于40μm.     

微小型零件自动装配的软件设计与实现

针对微小型零件的装配问题,搭建了四轴微装配系统,利用VC++平台开发了微小型零件自动装配软件,实现了可视化人机交互式装配.微装配系统软件设计模式采用分层架构的思想,通过分析类和对象的关系,采用创建类的方式封装了微装配软件系统架构的主要模块.软件模块包括运动控制、气动控制、图像采集与处理、模板数据管理、示教再现以及相机标定.采用面向对象的方式实现了各个模块间的数据交换,创建了机器视觉与示教再现相结合的自动装配控制模式.装配测试表明:该系统运行平稳,装配过程中无需人工干预,可以很好地实现不同尺寸微小型零件的自动装配;软件具有很好的重复性、人机交互性和稳定性.     

跨尺度微小型零件的测量与装配

针对跨尺度微小型零件的精密装配中显微视觉视场狭小与零件的特征尺寸跨度较大相矛盾的问题,研究了跨尺度零件的位姿检测技术,基于高、低倍显微视觉单元研制了自动装配系统,系统采用模块化体系结构及先看后动的装配控制模式.提出局部特征拼接法实现了跨尺度零件的定位测量,使用标定尺对系统坐标系之间的误差角进行了标定,采用参考基准法辅助对显微视觉单元切换后的装配基准进行定位.设计测试模板对系统测量精度进行了验证,结果显示高倍显微视觉单元的同轴度测量精度优于1.5 μm,平行度精度优于1μm.利用研制的装配系统进行了装配实验,实验结果表明,关键零件的装配精度满足工艺要求.该装配系统可稳定、可靠地完成跨尺度微小型零件的自动装配.     

基于真空吸附的微器件受力分析研究

微装配的对象主要是微米级或亚毫米级尺寸的微器件,这些微器件的轻、小、薄、软的特征对微夹持器的夹持方式和夹持力的控制提出了非常严格的要求和限制。本文针对平板类微器件设计了一种真空吸附式微夹持系统,不仅可以吸附不同形状和尺寸的零件,而且可以实现零件位姿的调整和接触力的检测。在只考虑范德华力的情况下,本文重点建立了微器件的吸附力学模型,为实现稳定吸附与释放提供了计算依据。最后完成了精度要求为平行度误差不大于8μm的微组件装配实验,装配效果良好。     

精密微小装配中的传感器与测量技术

装配是高性能精密微小器件或产品制造过程中的关键环节,由于零件及其关键结构的尺寸微小,微小装配必然是基于传感器与测量技术的精密装配。在微小零件装配过程中,需要精确测量待装配零件之间的相对位置和姿态的偏差,控制配合零件之间的接触力或接触状态。首先对用于精密微小装配的传感器技术进行了概述;然后结合精密微小装配中的应用需求,对机器视觉、力觉等主要传感器与测量技术进行了综述,并分析了精密测量与装配控制的技术与方法,旨在对精密装配相关的技术开发、装配设备研制提供参考和借鉴。     

精密微小装配系统柔性化技术

随着产品的微小型化, 人工装配作业的难度增大, 无法满足高性能微小器件装配的要求, 研制微小装配自动化设备是解决装配难题的有效途径。由于装配任务的多样化, 同时伴随着器件的改进或产品的升级, 以及缩短研发周期等诸多因素, 要求研制的微小装配设备能够对产品的快速变化做出响应。因此, 柔性化微小装配设备的研发是应对这一挑战的关键。本文重点介绍提升微小自动化装配系统柔性化的主要技术和方法, 即设备模块化方法和微小零件操作工具的自动换接, 并总结了研究进展, 在此基础上, 面向某一类微小器件的精密装配,提出了柔性微小装配设备的系统架构, 并简要介绍了基于这些系统架构所研制的精密微自动化装配设备。论文旨在为柔性化微小装配设备的研制提供一定的参考。     

某静子叶片焊接组件点焊装配夹具结构研究

某燃机静子叶片焊接组件,是由4-6个叶片电子束焊焊接而成,静子叶片单件之间尺寸公差较大,装配组件直接电子束焊焊接,零件定位不稳,焊接后组件变形大,也不利于电子束焊参数固化。所以,电子束焊焊接前必须进行点焊预装配,点焊预装配的精度就由点焊装配夹具来保证,点焊装配夹具设计有标准的基准面和找正带,通过百分表检测和叶片标准件的对比,调整叶片定位位置,解决组件之间尺寸公差大,不一致问题,解决电子束焊后静子叶片焊接组件精度和电子束焊参数固化。     

精密微小型零件自动装配系统显微机器视觉的照明自动优化

为了在微小型零件装配过程中始终获得质量最佳的零件图像,对显微视觉照明光强的自动优化问题进行了研究。为实现对零件的轮廓边缘与表面细节的照明,基于同轴光源与环形光源开发了照明自动控制系统。对比分析了四种图像质量评价函数的照明优化性能,提出了基于Roberts梯度和函数的图像质量评测方法,并应用于研制的装配系统。装配实验结果表明,光强优化过程快速准确,光强优化后目标边缘的对比度显著增强,消除了零件误识别现象,满足微小型零件高精度装配自动化的要求。     

基于改进差分进化算法的热电池装配机器人优化设计

目的 为了实现异形热电池组的智能化装配和解决装配过程中存在装配精度不高的问题,设计了一种装配机器人,并仿真验证该机器人是否能够满足异形热电池组的装配精度需求。方法 采用改进D-H参数法构建运动学模型,通过正运动学分析机器人末端轨迹。采用改进DE算法进行逆运动学求解,并通过仿真实验分析运动学求解结果。结果 求得平均位置误差为1.4×10–4 mm,平均姿态误差为2.4×10–4度,平均解迭代次数为219.857,各构件最大角速度不应超过3.5 rad/s。结论 设计的装配机器人能够满足异形热电池组装配精度要求,运动学求解精度提高2个数量级,效率提高72.5%。     

薄板件多工位装配尺寸误差建模与仿真

为保证薄板件装配尺寸精度,分析了两种主要误差源夹具尺寸误差和零件尺寸误差,尤其是定位销误差与零件孔间隙对装配尺寸误差的影响.采用状态空间法建立了薄板件多工位装配尺寸误差传递模型,并以某汽车地板薄板样件为例,运用所建立的尺寸误差模型对薄板样件进行仿真计算,仿真结果与实际测量结果进行对比,验证了模型的正确性和实用性.该模型可应用于多工位装配尺寸误差源诊断、装配过程夹具优化设计和装配过程稳定性分析等.     

Balancing mixed-model assembly lines: a computational evaluation of objectives to smoothen workload

Mixed-model assembly lines are widely used in a range of production settings, such as the final assembly of the automotive and electronics industries, where they are applied to mass-produce standardised commodities. One of the greatest challenges when installing and reconfiguring these lines is the vast product variety modern mixed-model assembly lines have to cope with. Traditionally, product variety is bypassed during mid-term assembly line balancing by applying a joint precedence graph, which represents an (artificial) average model and serves as the input data for a single model assembly line balancing procedure. However, this procedure might lead to considerable variations in the station times, so that serious sequencing problems emerge and work overload threatens. To avoid these difficulties, different extensions of assembly line balancing for workload smoothing, i.e. horizontal balancing, have been introduced in the literature. This paper presents a multitude of known and yet unknown objectives for workload smoothing and systematically tests these measures in a comprehensive computational study. The results suggest that workload smoothing is an essential task in mixed-model assembly lines and that some (of the newly introduced) objectives are superior to others.     

Sequencing mixed-model assembly lines to minimise the number of work overload situations

The mixed-model sequencing problem is to sequence different product models launched down an assembly line, so that work overload at the stations induced by direct succession of multiple labour-intensive models is avoided. As a concept of clearing overload situations, especially applied by Western automobile producers, a team of cross-trained utility workers stands by to support the regular workforce. Existing research assumes that regular and utility workers assemble side-by-side in an overload situation, so that the processing speed is doubled and the workpiece can be finished inside a station's boundaries. However, in many real-world assembly lines the application of utility workers is organised completely differently. Whenever it is foreseeable that a work overload will occur in a production cycle, a utility worker takes over to exclusively execute work, whereas the regular worker omits the respective cycle and starts processing the successive workpiece as soon as possible. This study investigates this more realistic sequencing problem and presents a binary linear program along with a complexity proof. Different exact and heuristic solution procedures are then introduced and tested. Additional experiments show that the new model is preferable from an economic point of view whenever utility work causes considerable setup activities, for example walking to the respective station.     

装配干扰的控制：Fuzzy—Petri网络系统帮助调整装配计划

复杂产品单件或小批量装配的流程，经常会受到许多干扰的影响。因此，装配管理人员必须使根据生产能力得出的中期装配计划不断更新，适应实际的装配流程，以确保达到预期的生产目标。一种干扰管理系统已经投入使用，以支持对生产有影响的决策。这一系统目前在克姆尼茨工业大学和亚琛工业大学机床和企业管理实验室（ＷＺＬ）的合作下应运而生。为了制定现行的装配计划，采用了以Ｆｕｚｚｙ－Ｐｅｔｒｉ网络为知识基础的专家系统，该系     

支持设计过程的装配可行域划分和零件定位求解

提出了支持设计过程的六种装配约束 ,根据装配约束的结合条件划分出装配可行区域、装配可能区域和装配不可行区域 .在装配可行区域的零件的位置是直接确定的 .在装配可能区域零件的位置要根据它们的约束组合条件和几何数据进行解释 ,然后计算零件的位置和方向 .在装配不可行区域 ,零件的位置不能求解 .装配可行区域的划分和零件位置的确定可以极高的效率支持产品的设计过程     

基于映射的产品装配建模技术研究

根据自顶向下的设计要求,提出基于映射技术的功能模型向装配模型的转换方法.通过信息实例化及规则表达,保证了映射技术的可行性.通过建立不同的实例库和Mapping表,较好实现了模型信息的转换.通过功能单元映射为装配单元,功能间约束映射为装配连接特征以及装配关系,实现了设计约束的自顶向下传递和功能设计与结构设计的集成.利用二叉树对模型交互进行装配序列化处理,保证了装配模型结构的完整性与可装配性.通过开发原型系统验证了该方法的可行性.     

Balancing parallel two-sided assembly lines

Two-sided assembly lines are usually designed to produce large-sized products such as automobiles, trucks and buses. In this type of production line, both left-side and right-side of the line are used. In parallel assembly lines, one or more product types are produced on two or more assembly lines located in parallel to each other. Both production lines have several serious practical advantages. For this purpose, in this paper, two or more two-sided assembly lines located in parallel to each other are considered and a tabu search algorithm which combines the advantages of both types of production lines is developed. To assess the effectiveness of the proposed algorithm, a set of test problems are solved. The proposed algorithm is illustrated with two examples, and some computational properties of the algorithm are given.     

Meeting demand variation using flexible U-shaped assembly lines

Nowadays, companies must be able to provide a higher degree of product customisation to fulfil the needs of the increasingly sophisticated customer demand. This can only be achieved by having flexible production systems, able to cope with extended product ranges and with the uncertainty and variability of demand in the current market environment. The purpose of this paper is to present a contribution related to facilities design that accounts for this issue, by presenting flexible U-shaped line configurations for an assembly system. In this type of line, whenever the production volume or product mix changes, the only modification in the line will be the number of operators working in the line, as the physical workstations remain fixed. The relevance of the problem is stated and a heuristic procedure, based on ant colony algorithms, developed to address this problem is described. The results of the application of the proposed procedure to an assembly line of a major manufacturer of electronic security systems are reported.     

Stochastic two-sided U-type assembly line balancing: a genetic algorithm approach

In this paper, a novel stochastic two-sided U-type assembly line balancing (STUALB) procedure, an algorithm based on the genetic algorithm and a heuristic priority rule-based procedure to solve STUALB problem are proposed. With this new proposed assembly line design, all advantages of both two-sided assembly lines and U-type assembly lines are combined. Due to the variability of the real-life conditions, stochastic task times are also considered in the study. The proposed approach aims to minimise the number of positions (i.e. the U-type assembly line length) as the primary objective and to minimise the number of stations (i.e. the number of operators) as a secondary objective for a given cycle time. An example problem is solved to illustrate the proposed approach. In order to evaluate the efficiency of the proposed algorithm, test problems taken from the literature are used. The experimental results show that the proposed approach performs well.