Design for assembly: A challenge for expert systems

Anticipating the increasing use of new and emerging computer technology in product engineering, design for assembly will be achieved effectively by applying advanced data processing technology and data management methods creating an assembly knowledge base and decision support system to close the loop between design, process planning and actual assembly. This paper introduces DFA and describes a strategic and conceptual approach to realise such a decision support system leading to an expert system for Design for Assembly in the near future.     

An expert system for assembly based on Axiomatic Design principles

Increasing demands for lower cost of goods, due to international competition, has developed a new area of rationalization for increased productivity which can be achieved by applying new radical methods of production principles. Design for Assembly (DFA) is one of such methods that should be considered in the early design stage in order to cope with the increasing demands of lower cost, improved working environment, and higher wages. When Axiomatic Design (AD) is implemented with DFA in an intelligent way, a new area of design concepts would be realized. This study examines some elements of intelligent design systems to assess manufacturability of a product through the development of a knowledge based expert system for assembly (KBESA). The knowledge base has been acquired from DFA along with AD concepts with emphasis on the conceptual design stage where the structure of the product as a whole is considered. These concepts have been implemented in a case study illustrating its applicability.     

虚拟环境下面向装配的设计系统的研究

虚拟环境下面向装配的设计,是一种集成虚拟现实技术和装配性评价的交叉学科研究,文中提出了一个虚拟环境下面 向装配的设计系统VirDFA(Virtual Design For Assembly)的体系结构,首先描述了虚拟人工实时拆卸的过程,着重研究在实现虚拟人工拆卸过程中,需要解决的装配体物性建模、虚拟环境下装配约束的动态管理及装配序列/路径的自动记录等关键技术,其次,从面向产品结构和装配工艺过程两方面的再设计角度,构建了装配性评价体系,提出了定量的装配效率模型和装配复杂度指标模型。并从装配成本的角度来评价产品的装配性优劣,为产品和装配工艺规划的再设计提供了依据。     

The design and development of an automated DFA system

This paper presents the design and development of an automated system to assist with Design for Assembly (DFA) analysis. The system is designed to accept information on alternative assemblies using DFA metaphors. Statistics are calculated for these assemblies so as to evaluate their assemblability. The alternative assemblies and improvements in any assembly design are evaluated using these statistics.

A binary tree data structure is used in the DFA system to represent the design data. This structure is implemented by a linked method with three links in each tree node. This allows any arbitrary tree to be represented efficiently, and it also allows for unpredictable tree growth and easy tree manipulation. The user interface of the DFA system is managed by the “User Interface Management System”, that achieves direct and fast control of the screen by directly accessing the video memory.     

Geometric and form feature recognition tools applied to a design for assembly methodology

The paper presents geometric tools for an automated Design for Assembly (DFA) assessment system. For each component in an assembly a two step features search is performed: firstly (using the minimal bounding box) mass, dimensions and symmetries are identified allowing the part to be classified, according to DFA convention, as either rotational or prismatic; secondly form features are extracted allowing an effective method of mechanised orientation to be determined. Together these algorithms support the fuzzy decision support system, of an assembly-orientated CAD system known as FuzzyDFA.     

Assembly line balancing in garment industry

Garment manufacturing is a traditional industry with global competition. The most critical manufacturing process is sewing, as it generally involves a great number of operations. The aim of assembly line balance planning in sewing lines is to assign tasks to the workstations, so that the machines of the workstation can perform the assigned tasks with a balanced loading. Assembly line balancing problem (ALBP) is known as an NP-hard problem. Thus, the heuristic methodology could be a better way to plan the sewing lines within a reasonable time.This paper develops a grouping genetic algorithm (GGA) for ALBP of sewing lines with different labor skill levels in garment industry. GGA can allocate workload among machines as evenly as possible for different labor skill levels, so the mean absolute deviations (MAD) can be minimized. Real data from garment factories and experimental design are used to evaluate GGA’s performance. Production managers can use the research results to quickly design sewing lines for important targets such as short cycle time and high labor utilization.     

Firefly-inspired algorithm for discrete optimization problems: An application to manufacturing cell formation

The canonical firefly algorithm is basically developed for continuous optimization problems. However, lots of practical problems are formulated as discrete optimization problems. The main purpose of this paper is to present the discrete firefly algorithm (DFA) to solve discrete optimization problems. In the DFA, we define a firefly's position in terms of changes of probabilities that will be in one state or the other. Then by using this metaheuristic algorithm, the manufacturing cell formation problem is solved. To illustrate the behavior of the proposed model and verify the performance of the algorithm, we introduce a number of numerical examples to illustrate the use of the foregoing algorithm. The performance evaluation shows the effectiveness of the DFA. The proposed metaheuristic algorithm should thus be useful to both researchers and practitioners.     

Managing DFA History with Queue for Deflation DFA

There is an increasing demand for network devices to perform deep packet inspection (DPI) in order to enhance network security. In DPI, the packet payload is compared against a set of predefined patterns that can be specified using regular expressions (regexes). It is well-known that mapping regexes to deterministic finite automaton (DFA) may suffer from the state explosion problem. Through observation, we attribute DFA explosion to the necessity of remembering matching history. In this paper, we investigate how to manage matching history efficiently and propose an extended DFA approach for regex matching called fcq-FA, which can make a memory size reduction of about 1,000 times with a fully automated approach. In fcq-FA, we use pipeline queues and counters to help record the matching history. Hence, state explosion caused by Kleene closure and length restriction can be completely avoided. Furthermore, it achieves a fully automated signature compilation with polynomial running time and space. The equivalence between fcq-FA and the traditional DFA is guaranteed by a strict theoretical proof, which means fcq-FA can process all the regexes supported by the traditional DFA.     

Time-Optimal Coordination of Flexible Manufacturing Systems Using Deterministic Finite Automata and Mixed Integer Linear Programming

Automation and flexibility are often mentioned as key concepts in modern production industry. To increase the level of flexibility, deterministic finite automata (DFA) can be used to model, specify and verify the production systems. Often, it is also desirable to optimize some production criteria, such as for example the cycle time of a manufacturing cell. In this paper, a method for automatic conversion from DFA to a mixed integer linear programming (MILP) formulation is first presented. This conversion is developed for a number of DFA structures that have shown to be useful in practical applications. Special attention is paid to reducing the search region explored by the MILP solver. Second, a conversion from the MILP solution to a DFA supervisor is described. This allows to combine the advantages of DFA modeling with the efficiency of MILP and supervisory control theory to automatically generate time-optimal, collision-free and non-blocking working schedules for flexible manufacturing systems.

DFA最小化算法研究

本文指出了现有DFA最小化算法的缺陷,并给出使用这些算法对DFA限制条件以及将不满足限制条件DFA等价转换成满足限制条件的DFA一般方法;在研究状态等价的充分条件基础上,提出了一种新的适用任何DFA的最小化算法及其算法的正确性证明。     

有限状态自动机的C#实现

基于Visual C#语言实现了有限状态自动机.该自动机具有小巧轻便、简单易用的优点,可应用于程序复杂界面的操作与控制.     

入侵检测系统中模式匹配自动机的构造研究

本文提出了一种新的用于构造入侵检测模式匹配自动机的方法。该方法从构造判定单个模式的NFA自动机入手,通过集成单个的NFA而得到全集的NFA,并将全集NFA转换为与之等价的DFA并化简,从而可得到全集的确定型模式匹配有限自动机。由于该方法可以完全自动完成,从而可以方便地为入侵检测系统构造模式匹配自动机。     

Automated array assembly: a high throughput, low cost assembly process for LIGA-fabricated micro-components

 The development of a viable LIGA-based micro-manufacturing capability requires the assembly of discrete micro-components into more complex devices. The size and tolerances of micro-components preclude the direct use of traditional macroscopic assembly process to micro-device manufacturing. Instead specific micro-assembly technologies must be developed and validated for producing complex micro-systems. Automated array assembly, a high throughput, low cost approach to micro-assembly, uses specialized fixtures allowing an array of micro-components to be picked-up and inserted into a corresponding array of devices using automated and highly accurate positioning stages. Assembly rates are measured here for insertion assembly experiments using automated array assembly and these rates compared with manual assembly rates. These results show that the automated array approach can assemble micro-components with rates at least an order of magnitude greater than manual assembly rates. Received: 25 August 1997/Accepted: 3 September 1997     

基于二分图的装配体检索研究

基于事例推理是解决DFA和装配工艺规划问题的有效方法,装配体检索是应用此方法的关键步骤．对装配体中的联结关系进行表达和分类,提出联结关系定量的比较方法,基于二分图理论建立了装配体之间的相似计算模型,给出了装配体检索过程和计算实例．     

The strategic design and development of ERP and RTMS

One of the crucial requirements of global manufacturing strategy is the ability to optimise the use of information technology. This paper describes a process to implement manufacturing strategies that are consistent with a particular company's overall business strategies and results with conceptual system architecture. A methodology is proposed and used to identify and implement an integrated manufacturing strategy which consists of two major horizons: Enterprise Resources Planning (ERP) and a Real-Time Monitoring system (RTMS). RTMS, which can provide up-to-date information for the planning and scheduling of manufacturing orders, monitoring quality, improving communication and increasing productivity, is implemented and is integrated with an ERP system. The architecture of the ERP system is designed for a global manufacturing environment. The implementation was designed with a Distributed Object-Oriented Technology (DOOT) which increases the system scalability, configurability, flexibility and interoperability. The ERP is designed to support real-time data collection and processing for all required production and inventory analysis with a flexible architecture which can meet the distributed business requirements.     

A collaborative and integrated platform to support distributed manufacturing system using a service-oriented approach based on cloud computing paradigm

Today's manufacturing enterprises struggle to adopt cost-effective manufacturing systems. Overview of the recent manufacturing enterprises shows that successful global manufacturing enterprises have distributed their manufacturing capabilities over the globe. The successes of global manufacturing enterprises depend upon the entire worldwide integration of their product development processes and manufacturing operations that are distributed over the globe. Distributed manufacturing agents' collaboration and manufacturing data integrity play a major role in global manufacturing enterprises' success. There are number of works, conducted to enable the distributed manufacturing agents to collaborate with each other. To achieve the manufacturing data integrity through manufacturing processes, numbers of solutions have been proposed which one of the successful solutions is to use ISO 10303 (STEP) standard. However, adopting this standard one can recognize antonym effects of integration and collaboration approaches that weaken both integration and collaboration capabilities of manufacturing agents. In our latest work, we had developed an integrated and collaborative manufacturing platform named LAYMOD. Albeit the platform in question was through enough to be applied in various collaborative and integrated CAx systems, its embedded structure hampers its application for collaboration in distributed manufacturing systems. To achieve an integrated and collaborative platform for distributed manufacturing agents, this paper proposes a service-oriented approach. This approach is originated from cloud computing paradigm known as one of the technologies which enables a major transformation in manufacturing industry. Also, to maintain the product data integration based on the STEP standard, a new service-oriented approach is proposed. This approach is in parallel to the new capability of the STEP standard for supporting XML data structures. The result is a new platform named XMLAYMOD. XMLAYMOD is able to support distributed manufacturing collaboration and data integration based on the STEP standard. The different aspects of this platform to fulfill the requirements of distributed collaboration and also to overcome the lacks of the STEP standard are discussed through a brief case study.     

Task-board task for assembling a belt drive unit

ABSTRACT

A task board is a board for assembling parts, developed to test the abilities of a robot system to perform assembly operations associated with a manufacturing process. This study describes a task board that can serve as a basis for developing program modules for assembling a specific product. A properly designed task board can serve as a preliminary template for a specific assembly and can promote robotic assembly. This study analyzes the design of a Task-board task performed at the World Robot Summit 2018 (WRS 2018). The main competitive task at the WRS 2018 was the assembly of a belt drive unit. Analyses showed that the directions of assembly, especially the horizontal direction, were common difficulties in both Task-board and Assembly task competitions. Development of a task board for a specific assembly product requires an increase of its relevance to the assembly product, such as using the same workpieces or using similar assembly orientations.     

Using past manufacturing experience to assist building the yield forecast model for new manufacturing processes

Polarizers are one of the key parts of Thin-Film Transistor Liquid-Crystal Displays (TFT-LCD), and their production requires high material costs. How to reduce manufacturing costs is thus a key task in this highly competitive global market. The precise yield forecast model considering learning effects that is proposed in this work is believed to be an effective approach to reduce both the raw material input-cost and inventory cost of overproduction. Support vector regression (SVR) model is one of the commonly used approaches to forecast the yield trend. However, in the early manufacturing stages for a new product, an SVR model is usually sensitive and unstable because of the use of insufficient data. Faced with this problem, this research aims at enhancing the SVR model by using past manufacturing experience and virtual samples to estimate the yield trend model for pilot products. This paper proposes a novel Quadratic-Curve Diffusion (QCD) method, wherein we derive a quadratic yield function (QYF) of the new manufacturing process for each key manufacturing variable by utilizing past manufacturing experience; and then use the QYF to generate virtual samples to assist building the overall yield forecast model of the new manufacturing process. The results show that the proposed method is superior to the performance of other forecast and virtual sample generation models.     

Multi-attribute negotiation mechanism for manufacturing service allocation in smart manufacturing

Smart manufacturing is undergoing rapid development along with many disruptive technologies, such as Internet of Things, cyber-physical system and cloud computing. A myriad of heterogeneous manufacturing services can be dynamically perceived, connected and interoperated to satisfy various customized demands. In smart manufacturing, the market equilibrium is variable over time due to changes in demand and supply. Thus, efficient manufacturing service allocation (MSA) is critical to implementation of smart manufacturing. This paper considers the MSA problem under market dynamics with maximization of utility of customers and service providers. Many conventional methods generally allocate manufacturing services to the customers by multi-objective optimization without considering the impact of interactions between customers and service providers. This paper presents a multi-attribute negotiation mechanism to address the MSA problem under time constraints relying on autonomous agents. The proposed negotiation mechanism is composed of two models: an atomic manufacturing service negotiation model and a composite manufacturing service coordination. The former model is based on automated negotiation to seek an atomic manufacturing service over multiple attributes for an individual subtask. The latter model incorporates the global distribution and surplus redistribution to coordinate and control multiple atomic manufacturing service negotiations for the whole manufacturing task. Numerical studies are employed to verify the effectiveness of the multi-attribute negotiation mechanism in solving the MSA problem. The results show that the proposed negotiation mechanism can address the MSA problem and surplus redistribution can effectively improve the success rate of negotiations.