通用的灵活性装配系统的模拟

外文翻译专 业 机械设计制造及其自动化 外文资料名称：Simulation of a generic flexible assemblysystem N.F.EDMONDSON and A.H.REDFORD (用外文写)外文资料出处：INT.J.COMPUTER INTEGRATED MANUFACTURING,2003,VOL.16,NO.3，157172附 件： 1.外文资料翻译译文 2.外文原文 指导教师评语： 签名： 年 月 日计算机集成制造2003年，第二卷。VOL 16 NO 3 ， 157 172通用的灵活性装配系统的模拟埃德蒙德森，雷德福 冯洁译 摘要：在八十年代初，一个概念灵活性装配机在1983年首先提出 。在此之后，各种不同的研究项目，已先后进行了研究，希望建立一种灵活的制度，即在功能上和经济上可行的。最显著的贡献，是已经取得了所通过欧联盟的“FAMOS -INFACT ”项目 又称321项目。然而发展过程中取得的这些项目，却没有工业基础的系统存在。本文提出了一种仿真模型的一个崭新的概念，为多站灵活性自动装配机，并研究应用一种基于规则的控制策略控制的一个材料处理系统中使用了这样的作用。1 、导言讨论灵活性装配，了解传统的专用装配的局限性是很重要的。专用技术是为一个大规模生产的技术开发，在20世纪初由亨利福特，装配了独特的产品，相对非常大的量，这导致了一种极具成本效益的解决方案。专用装配自动化装配任务，将其打散成各个简单操作，让它可以进行一系列的重组，装配正在建立的，因为它将呈持续上升趋势。零部件供应散装，放置在个别部分馈线，并提交自动重组，其插入到部分装配在高速增长。这种形式的工作可以达到周期的时候，即尽可能少的低于每个装配1秒。 作为专用组合机，只适合单一产品，任何重大的产品设计变化将导致相当装配机，重新设计成本，以及漫长的重构时间。它还明确指出，这种设备只能是正当的大批量生产，因为设备的成本是散布在整个单一产品的发展过程中。基于这个原因，专用装配的应用程序历来而受到限制，以高投入量产。此外，在世界市场上的要求是，产品品种更多，一致的高品质，更短的交货时间，价格竞争力的产品和快速推出的新产品。在斯堪的纳维亚国家，这些因素正伴随着与日俱增的劳工成本。在主体，产品装配仍然是一个手动过程中，受到质量变化，、生产力，、在劳动率和卫生和安全问题波动的影响。在设法减少产品装配成本，许多欧洲公司都提出自己的组装厂，以较低的成本区域。不过，这总不是理想的解决办法，因为它增加了运输成本问题，地方的一种物理性屏障设计和生产，并患有质量变异。 采用半自动装配（见图1 ）已是一种办法，是通过产业，以解决与人工装配有关的问题。半自动装配自动化的关键零件的装配顺序，如拧或压接式业务，而经营者履行组成部分的原料提供和定位任务。这就使得手工装配任务历来受到质量变化，以控制使用自动化和昂贵的部分，喂养和操纵执行的任务采用低成本的劳动力。不过，半自动化装配，还需要进行大量投资在专用模具上，并且仍然受生产率和劳工率波动的影响。 低成本的装配系统的优点才有可能消除，如果有足够的自动化可以被引入到这一装配系统（菲尔德曼等， 1996年） ，随着生产系统已不再是依赖于大量的人。该装配厂能贴近客户市场，以减少后勤成本。驱动因素的背后，设计和开发的灵活性装配系统是经济学。如前所述，这是不符合经济原则，以建立一个专用装配机，为小批量的生产量（ 30000至500000单位/年） ，但装配的一部分费用将过高。主要目标，因此，大力发展灵活装配机，是最小的特殊用途设备，即设备可以摊销针对该产品。这将允许更多的不仅仅是一个产品类别，以组装，对机器和机器的成本摊生产更多的产品。 灵活性装配采用装配机器人及灵活性部分馈线，以创造一种混合的手动，半自动和专用装配，是有能力小批量，多产品品种的生产。灵活性装配机，可看作数控加工站（见图2 ） 。部分节目，固定装配，工具及原料成分是该系统的投入，成品是这个结果。 有三个基本的自动灵活性装配系统的配置，单站，多站和自动灵活性装配生产线。图3显示了单站系统，装配机器人（机器人） ，是设在中心的系统及零件馈线设于周边的机械手的工作区。作为一个单一的机械手进行所有的装配任务，在系列产品中，装配时间，可以成为长期的，如果装配有许多零件。如果一个装配零部件的数量变得过大，则可能不能使用，以适应他们周围的机械臂周长和较大的机械臂将要克服这些问题，可用于多站布局（见图4 ） 。装配的运作，是可以分解成小团体执行的任务，在大会的一些车站，机械臂访问每一个大会监测站循序渐进的方式进行。为了使这一可能，夹具转移制度规定，增加了系统的成本。这种做法使产品具有更多的组件组装以更快的速度比单站系统。至目前为止，只有在商业上的成功实施灵活性装配已灵活性线装配（见图5 ） ，在那里一些机器人的使用，以取代专用工作头使用于专用装配线，每个机器人负责每个装配的几个部分定位一直是一个索引传输系统。这样的装配系统，能够大批量生产的单一产品有很多变种，例如，索尼随身听或摄影机的装配（ 惠特尼公司， 1999年） 。这些系统商业上的成功是由于高量产的单一产品，使单位成本的生产在经济上是可以接受的。 开发一个通用的灵活性装配系统涉及到的设计，选择和整合多种不同的机械系统，以建立一个装配系统，能够组装各种各样的产品，有一个不知名的规格。一个具体的系统配置，是依赖于多种因素，如产品尺寸，重量，元件插装方向，和机械臂的几何形状。灵活性装配的理念首次引入（ 1983 ） 。有人认为，这种系统将被用于组装中的各种生产量之间的人工装配和专用装配。二十年后，并没有这种制度存在，因为在商业上可用的系统，低容积大会仍然是一个手动或半自动过程中，美联储同时表示，尽管劳工成本的50 ， 70 的费用比以前降低了机器人技术和显着改善的表现，机器人技术（德尔加多2001年） 。 这个文件审查申请的以规则为基础的控制策略，为控制物料处理系统中使用的多站灵活性自动装配系统。2 .装配的工作空间布局埃德蒙德森和雷德福（2001年）确定最合适的布局，为各装配单元的内容是如图一所示7 。 两个装配使用，在装配单元，使该机器人可以直接进入第二个装配时，所有的装配任务就第一个装配夹具已经完成，而物料搬运系统删除，并取代完成的装配。这使得第一个装配被移走，并用该材料处理系统，而不需要为机器人停止工作，从而最大限度地利用机械臂。此外，当时机械臂花表演夹持器和工具的变化，是尽量减少装配的倍数，对产品的每一个夹具;这样，所需要的时间来履行手动变化是分布在一些产品中，作为反对以单一产品，以及物料处理系统，不须更换装配夹具，为每一个产品组装。 为了达到适当的生产速度，一些单元可以联系在一起，形成一个装配线（见图8 ） 。每一个装配单元有自成一体的材料处理系统，其中与其他装配系统互动通过一个传递机制。结果是，没有需求的增加，对物料处理系统，是有经验的时候，一系列的细胞连在一起，所以不会让机器等待处理系统提供部分材料。3、材料处理系统多站灵活性自动装配机，可视为两个基本的机械系统：平行运作，拟人机器人；后者从事实际的装配任务，以及物料装卸设备，以确保该机器人是美联储有了正确的零件，固定装置和工具，在正确的时间和地点，同时履行其他职能，如成品免职集结地域。雷德福（ 1991 ）列出了总材料处理要求如下： 处理零部件纳入这一体系。 零部件分为两组，那些可以处理用传统的小零件，进料器，如：振动一反馈线，以及那些不能提供使用小部分反馈线。 处理托盘，固定装配和工具。除了向装配提供零部件，材料处理系统，也将需要处理托盘的零件，装配和技术转让的工具和带出这个装配机。从系统中清除已完成的产品，。成品组件必须从装配中被清除掉，这个功能是从装配中收集产品及传递材料清除系统。这种形式可以是一个简单的输出即存款产品于其它成品在一个伪随机的方式。然而，在大多数情况下，该产品已被一些其它形式的设备处理，如：测试，加工或包装，因此，将是合乎逻辑的，以保持产品的位置和方向。这可以用某种形式的机械转换装置，它促使产品直接交给下一任的程序。反过来说，如果该程序的进程，是不是在近距离向装配系统或一个存储缓冲区，是需要该产品可放置在某种形式的包装，如：托盘或暗盒，使之后的过程中可以自动卸下包装。INT. J. COMPUTER INTEGRATED MANUFACTURING, 2003, VOL. 16, NO. 3, 157172Simulation of a generic flexible assembly systemN. F. EDMONDSON and A. H. REDFORDAbstract. During the early 1980s, the concept of a flexible assembly machine was first suggested by Hounsfield (1983). Following this, a variety of research projects have been conducted in an attempt to develop a flexible assembly system that is functional and economically viable. The most significant contribution has been made by the EURICA EU 321 - FAMOS -INFACT project. However, despite the developments made during these projects, no industrial based system exists today. This paper presents a simulation model of a novel concept for a multi-station flexible automatic assembly machine, and examines the application of a rule based control strategy for the control of a materials handling system used in such a system.1. IntroductionBefore discussing flexible assembly it is important to understand the limitations of traditional dedicated assembly. Dedicated assembly is a mass production technology that was developed in the early 1900s by Henry Ford, to assemble a unique product in very large volumes, and this led to a very cost effective solution. Dedicated assembly automates the assembly task by breaking it down into simple operations that can be conducted by a series of workheads, the assembly being built up as it passes down the line. Parts are supplied in bulk, placed in individual parts feeders and presented to automatic workheads, which insert them into the part assembly at high speed. This form of assembly can achieve cycle times of as little as 1 second per assembly.As dedicated assembly machines are only suitable for a single product, any significant product design change will result in considerable assembly machine redesign costs, and lengthy reconfiguration time. It is also clear that such equipment can only be justified for large production volumes, as the equipment cost is spread over the life of a single product. For this reason, the application of dedicated assembly has traditionallybeen restricted to high volume production. Furthermore, the world market is demanding greater product variety, consistent high quality, shorter lead times, competitively priced products and rapid new product introduction. In Scandinavian countries, these factors are now accompanied by increasing labour costs.In the main, product assembly has remained a manual process, being subject to quality variations, fluctuations in productivity, fluctuations in labour rates and health and safety issues. In an attempt to reduce the cost of product assembly, many European companies have moved their assembly plants to lower cost regions. However, this is not always the ideal solution as it increases transportation costs, places a physical barrier between design and production and suffers from quality variations.The introduction of semi-automatic assembly (see figure 1) has been one approach adopted by industry to counter the problems associated with manual assembly. Semi-automatic assembly automates critical parts of the assembly sequence, such as screwing or push-fit operations whilst an operator performs the part feeding and positioning tasks. This enables the manual assembly tasks that traditionally suffer from quality variations to be controlled using automation and the costly part feeding and manipulation tasks to be performed using low cost labour. However, semi-automatic assembly still requires a significant investment in dedicated tooling and remains subject to fluctuations in production rates, and fluctuations in labour rates.The advantages of assembling in low cost regions can be eliminated if sufficient automation can be introduced into the assembly system (Fieldman et al. 1996), as the production system is no longer reliant on large numbers of people. The assembly plant can then be placed close to the customer market to reduce logistical costs.The driving factor behind the design and development of flexible assembly systems is economics. As previously stated, it is not economically viable to build a dedicated assembly machine for small batch production quantities (30 000 to 500 000 units/year), as the piece part cost of assembly will be too high. The main goal, therefore, behind the development of a flexible assembly machine is the minimization of special purpose equipment, i.e. the equipment that can be amortized against the product. This will allow more than just one product type to be assembled on the machine and the machine cost to be spread over the production of more products.Flexible assembly utilizes assembly robots and flexible part feeders in order to create a hybrid of manual, semi-automatic and dedicated assembly that is capable of small batch, large product variety production. The flexible assembly machine can be compared with a CNC machining station (see figure 2). Part programs, fixtures, tools and raw components are the system input, and finished products are the result.There are three basic automatic flexible assembly system configurations, Single Station, Multiple Station and Automatic Flexible Assembly Line. Figure 3 shows a Single Station system, the assembly robot (manipulator) is located at the centre of the system and the parts feeders are located at the perimeter of the manipulator work zone. As a single manipulator performs all of the assembly tasks in series, the assembly time can become long if the assembly has many parts. If the number of parts in an assembly becomes too large, it may not be possible to fit them around the manipulator perimeter and a larger manipulator will have to overcome these problems, a Multiple Station layout can be used (see figure 4). The assembly operation is broken down into small groups of tasks performed at a number of assembly stations, the manipulator visits each of the assembly stations progressively. IN order to make this possible, a fixture transfer system is required that increases the system cost. This approach enables products with more components to be assembled with greater speed than a single station system.To date the only commercially successful implementation of flexible assembly has been Flexible Line Assembly (see figure 5), where a number of manipulators are used to replace the dedicated workheads used in dedicated assembly lines, each manipulator performing a few assembly tasks at each assembly station positioned along an indexing transfer system. Such assembly systems are capable of high volume production of a single product having many variants, for example, the Sony Walkman or the assembly of video cameras (Whitney, 1999). The commercial success of these systems is due to the high production volumes of a single product, making the cost per unit of production economically acceptable. The development of a generic flexible assembly system involves the design, selection and integration of a number of different mechanical systems in order to develop an assembly system that is capable of assembling a wide variety of products having an unknown specification. A specific system configuration is dependent on a variety of factors, such as product size, weight, component insertion direction, and manipulator geometry.The concept of flexible assembly was first introduced by Hounsfield (1983). It was argued that such systems would be used to assemble the middle range of production volume between manual assembly and dedicated assembly (Lotter 1986). Twenty years later, no such systems exist as commercially available systems, and low volume assembly remains a manual or semi-automatic process, despite the rise in the cost of labour by 50%, a 70% reduction in the cost of robot technology and a significant improvement in the performance of robotic technology (Delgado 2001).This paper examines the application of a rule-based control strategy for the control of the materials handling system used in the multi-station flexible automatic assembly system.2. Assembly workspace layoutEdmondson and Redford (2001c) identified that the most suitable layout for the various assembly cell elements is as shown in figure 7.Two assembly fixtures are used in the assembly cell so that the manipulator can move directly to the second assembly fixture when all of the assembly tasks on the first assembly fixture have been completed, whilst the materials handling system removes and replaces the completed fixture of assemblies. This allows the first assembly fixture to be removed and replaced by the materials handling system without the need for the manipulator to stop working, hence maximizing the manipulator utilization. Furthermore, the time the manipulator spends performing gripper and tool changes is minimized by assembling in multiples of products on each fixture; in this way, the time taken to perform a gripper change is distributed across a number of products as opposed to a single product, and the materials handling system is not required to replace an assembly fixture for each product assembled.In order to achieve an appropriate production rate, a number of cells can be linked together to form an assembly line (see figure 8). Each assembly cell has a self-contained materials handling system, which interacts with the other assembly systems via a transfer mechanism. The result is that no increase in demand on the material handling system is experienced when a series of cells are linked together, and it is unlikely that the manipulators will have to wait for the handling system to supply parts.3 Materials handling systemThe multi-station flexible automatic assembly machine can be considered as two basic mechanical systems which operate in parallel; the anthropomorphic manipulator, which performs the actual assembly task, and the materials handling equipment, which ensures that the manipulator is fed with the correct parts, fixtures and tools at the correct time and place, whilst performing other functions such as finished product removal from the assembly area. Redford (1991) lists the total material handling requirements