Distributed intelligent control of exceptions in reconfigurable manufacturing systems

In order to react to the continuous and unpredictable changes in product demand, in product variety, and in process technologies, reconfigurable manufacturing systems allow quick adjustment of production capacity and functionality by rearranging or changing their modular components. In this kind of system, operation management issues, such as exception handling policies, become more complex since correct reconfiguration strategies have to be selected. This paper explores the potential of the reconfigurability feature to be a basis for the development of new strategies to handle out-of-the-ordinary events in the production process; in particular, maintaining production flow when machine breakdowns occur. Decisions regarding how to deal with exceptions to the production process are complex and depend on the manufacturing system configuration and on many performance and economic variables. The authors propose agent-based manufacturing control for exception handling because of its ability to be very agile, as well as being reactive and efficient. Manufacturing agents, while working to pursue their specific goals, achieve the global target of the system. Complex decisions can be made due to the synergy arising from the agents' internal reasoning and the negotiation process among these agents. The adopted negotiation mechanism is based on the contract-net protocol, while different strategies have been designed for the internal reasoning. The authors demonstrate that, under certain conditions, an agent's internal strategies based on fuzzy reasoning improve the global performance of the system. The proposed control model has been tested on a discrete event simulation test-bed.     

Configuration design of scalable reconfigurable manufacturing systems for part family

Intense global competition, dynamic product variations, and rapid technological developments force manufacturing systems to adapt and respond quickly to various changes in the market. Such responsiveness could be achieved through new paradigms such as Reconfigurable manufacturing systems (RMS). In this paper, the problem of configuration design for a scalable reconfigurable RMS that produces different products of a part family is addressed. In order to handle demand fluctuations of products throughout their lifecycles with minimum cost, RMS configurations must change as well. Two different approaches are developed for addressing the system configuration design in different periods. Both approaches make use of modular reconfigurable machine tools (RMTs), and adjust the production capacity of the system, with minimum cost, by adding/removing modules to/from specific RMTs. In the first approach, each production period is designed separately, while in the second approach, future information of products’ demands in all production periods is available in the beginning of system configuration design. Two new mixed integer linear programming (MILP) and integer linear programming (ILP) formulations are presented in the first and the second approaches respectively. The results of these approaches are compared with respect to many different aspects, such as total system design costs, unused capacity, and total number of reconfigurations. Analyses of the results show the superiority of both approaches in terms of exploitation and reconfiguration cost.     

论制造系统模式的新进展

分析了制造系统模式变迁的原因；论述了现代制造系统模式的新特征，即客户化动态系统、可变性、自组织、自治与协调、全生命周期高的成本效率以及集成进化；提出了支持现代制造系统模式的若干关键技术，包括时变制造过程建模、自适应生产管理以及现代集成技术等；介绍了可重构制造系统、多智能代理制造系统、子整制造系统以及虚拟生产系统等现代制造系统；并从工业工程的角度，讨论了发展中国现代制造系统模式的若干问题，即改变金字塔式的集中管理组织结构，合理地发挥人的作用以及重视信息技术的应用。     

基于X列表的可重构ERP系统研究

为了从体系结构和管理机理更新的角度实现ERP的可重构性,建立了包括结构模型、过程模型、价值模型和分布式决策模型的X列表体系抽象层次结构.该模型能够通过初始化重构适应不同的企业环境,能够进行维护性动态重构以适应企业发展不同阶段上的环境变化,并能够支持企业内和企业间的集成与重构.给出了基于X列表的可重构ERP的软件系统架构.上述模型可以为新一代ERP软件系统的开发提供有力的理论支持.     

Coherence region of the Priority‐AND gate: Analytical and numerical examples

In recent years, the need for a more accurate dependability modelling (encompassing reliability, availability, maintenance, and safety) has favoured the emergence of novel dynamic dependability techniques able to account for temporal and stochastic dependencies of a system. One of the most successful and widely used methods is Dynamic Fault Tree that, with the introduction of the dynamic gates, enables the analysis of dynamic failure logic systems such as fault‐tolerant or reconfigurable systems. Among the dynamic gates, Priority‐AND (PAND) is one of the most frequently used gates for the specification and analysis of event sequences. Despite the numerous modelling contributions addressing the resolution of the PAND gate, its failure logic and the consequences for the coherence behaviour of the system need to be examined to understand its effects for engineering decision‐making scenarios including design optimization and sensitivity analysis. Accordingly, the aim of this short communication is to analyse the coherence region of the PAND gate so as to determine the coherence bounds and improve the efficacy of the dynamic dependability modelling process.     

Numerical simulation of an advanced energy storage system using H2O–LiBr as working fluid, Part 1: System design and modeling

The advanced energy storage technology proposed and patented by authors can be applied for cooling, heating, dehumidifying, combined cooling and heating, and so on. It is also called the variable mass energy transformation and storage (VMETS) technology in which the masses in one or two storage tanks change continuously during the energy charging and discharging processes. This paper presents an advanced energy storage system using aqueous lithium bromide (H₂O–LiBr) as working fluid. As one of VMETS systems, this system is a closed system using two storage tanks. It is used to shift electrical load and store energy for cooling, heating or combined cooling and heating. It is environmental friendly because the water is used as refrigerant in the system. Its working principle and process of energy transformation and storage are totally different from those of the traditional thermal energy storage (TES) systems. The electric energy in off-peak time is mostly transformed into the chemical potential of the working fluid and stored in the system firstly. And then the potential is transformed into cold or heat energy by absorption refrigeration or heat pump mode when the consumers need the cold or heat energy. The key to the system is to regulate the chemical potential by controlling the absorbent (LiBr) mass fraction or concentration in the working fluid with respect to time. As a result, by using a solution storage tank and a water storage tank, the energy transformation and storage can be carried out at the desirable time to shift electric load efficiently. Since the concentration of the working solution in the VMETS cycle varies continuously, the working process of the VMETS system is dynamic. As the first part of our study, the working principle and flow of the VMETS system were introduced first, and then the system dynamic models were developed. To investigate the system characteristics and performances under full-storage and partial-storage strategies, the numerical simulation will be performed in the subsequent paper. The simulation results will be very helpful for guiding the actual system and device design.     

可重构路由器研究的现状与展望

随着新业务和新应用的不断推出,传统路由器在业务升级能力及升级响应速度方面已不能满足网络发展的需求。实时电路重构技术利用可编程器件可多次重复配置逻辑状态的特性,能够在系统运行时根据需要动态地改变系统的电路结构,利用可重构技术实现的路由器能够支持新业务模块的硬件电路在芯片内动态加载,同时又不影响其他功能模块的正常运行,为传统路由器功能扩展能力差问题提供了解决思路。在介绍可重构技术的基本概念和支撑器件的当前发展概况后,对以往的可重构路由器技术和当前的研究现状进行了总结,并从构建可重构网络的角度分析了进一步的研究方向。     

Set-up games: a heuristic game-theoretic approach to set-up decisions for heterarchical manufacturing systems

Heterarchical control systems have emerged as promising alternatives to conventional centralized and hierarchical shop floor control systems. However, research to date has largely ignored long-term control issues such as the timing of resource reconfigurations, which are vital for the avoidance of myopic decision-making. As traditional analysis techniques implicitly assume centralized analysis and implementation of policies, they are not directly applicable to heterarchical environments. A non-cooperative game-theoretic planning technique for autonomous analyses of reconfiguration decisions by heterarchical machine controllers is described. Under the proposed system, a machine controller evaluates a set-up game to determine appropriate actions when faced with a sequence-independent reconfiguration decision. The prescribed action is defined by a pure or mixed-strategy equilibrium of the set-up game. By evaluating a game, the machine controller accounts for the potential actions and reactions of other machine controllers in the system. The approach allows the autonomous machine controller to make set-up decisions about future actions while preserving the independence characteristic of controllers in heterarchical environments.     

The impact of maintainability on the manufacturing system architecture

The rapid development of big data technologies can improve the maintainability of machines and equipment in manufacturing systems, which could impact the selection of the optimal system architecture. In this paper, two typical architectures for large manufacturing systems ? serial lines in parallel and reconfigurable manufacturing systems ? are considered, and their productivities are compared. A decision locus is calculated that divides the configuration space into two areas; in each area, one of the architectures is the preferred one. It is also investigated how the locus is affected by different parameters, such as system size, buffer capacity and machine or gantry maintainability. The analysis provides valuable managerial insights for designing the architecture of large manufacturing systems.     

On Cost‐effective Reuse of Components in the Design of Complex Reconfigurable Systems

Design strategies that benefit from the reuse of system components can reduce costs while maintaining or increasing dependability—we use the term dependability to tie together reliability and availability. D3H2 (aDaptive Dependable Design for systems with Homogeneous and Heterogeneous redundancies) is a methodology that supports the design of complex systems with a focus on reconfiguration and component reuse. D3H2 systematizes the identification of heterogeneous redundancies and optimizes the design of fault detection and reconfiguration mechanisms, by enabling the analysis of design alternatives with respect to dependability and cost. In this paper, we extend D3H2 for application to repairable systems. The method is extended with analysis capabilities allowing dependability assessment of complex reconfigurable systems. Analysed scenarios include time‐dependencies between failure events and the corresponding reconfiguration actions. We demonstrate how D3H2 can support decisions about fault detection and reconfiguration that seek to improve dependability while reducing costs via application to a realistic railway case study. Copyright © 2017 John Wiley & Sons, Ltd.     

Framework for quiescence management in support of reconfigurable multi-threaded component-based systems

In component-based software systems, the basic building block is the component, and applications are built as component compositions. `Dynamic reconfiguration` in such systems is defined as the ability to replace individual components at runtime, or to change the compositional topology by adding/removing components and/or changing the patterns of their interconnection. A `quiescence service` supports dynamic reconfiguration by pushing a system into a stable state in which such changes can be safely made. It is thus a key enabler of dynamic reconfiguration. The authors present the design of a quiescence service, which has been implemented for the OpenCOM component-based programming platform. It is argued that this design shows significant advances over the state of the art in quiescence support for component-based systems. In particular, it minimises programmer overhead and system disruption, and efficiently supports a large class of systems without imposing architectural constraints.     

Component reuse based agile reconfiguration for Enterprise Resource Planning (ERP) systems in manufacturing enterprises

Continuously changing business environments require Enterprise Resource Planning (ERP) systems of modern manufacturing enterprises have the ability of agile reconfiguration to adapt to changes with quick responses. Based on a deep analysis of benefits that component technology provides to agile reconfiguration, the paper presents the architecture of component-based ERP systems in which the high efficiency for system construction and reconfiguration is supported by multiple grained component coexistence. A unified feature-oriented component model and the full life cycle of component-based ERP are then presented, and the paper expatiates on the process and artifices of ERP agile reconfiguration based on component reuse, with emphasis on component matching and selection problem, in which an approximately optimal component set is chosen from a component library by minimizing the matching cost to adapt to changes. Finally a practical case, i.e. reconfigurations on a production planning system, is put forward to validate the effectiveness of this method.     

Application of the parameter plane method to the design of a digital power system stabilizer

Abstract

Stabilization of electric power systems is examined in this paper using a digital proportional‐plus‐integral (PI) stabilizer. Parameter‐plane method is proposed for the determination of the optimal gains for the PI stabilizer. For the purposes of comparison, the least‐square‐error approach is also presented for the design of a digital PI stabilizer. The effectiveness of the proposed PI stabilizer is illustrated by the digital simulation of a single‐machine‐infinite‐bus system. It is found that the proposed stabilizer can be employed as an effective means of improving the dynamic stability of the power system.     

Load sharing in series configuration

In reliability engineering, load sharing is typically associated with a system in parallel configuration. Examples include bridge support structures, electric power supply systems, and multiprocessor computing systems. We consider a reliability maximization problem for a high‐voltage commutation device, wherein the total voltage across the device is shared by the components in series configuration. Here, the increase of the number of load‐sharing components increases component–level reliability (as the voltage load per component reduces) but may decrease system–level reliability (because of the increased number of components in series). We provide the solution for the 2 popular life‐load models: the proportional hazard and the accelerated failure time models with the underlying exponential and Weibull distributions for both a single and dual failure modes.     

格网中p-cycles重配置的快速实现算法

提出了一种用于双链路故障恢复和为动态业务提供保护的p-cycles重配置启发式算法.该算法可以提供网络生存性设计和网络管理的高效性和简洁性,并能提供快速的恢复操作.仿真结果表明,这种算法用于双链路故障恢复的重配置容量冗余度可达74%,平均计算时间为48ms;用于增量重配置的双故障冗余度为118%,计算时间为81ms.基于该算法的业务恢复可以满足大多数业务的最低可中断时间要求.分析表明该算法亦适用于动态业务的p-cycles重配置.     

Recent advances in research on reconfigurable machine tools: a literature review

A recent trend in research on reconfigurable manufacturing systems is the development of reconfigurable machine tools (RMTs). A RMT can be used as a group of machines through change of its configuration to satisfy different manufacturing requirements. A literature review is provided in this paper to demonstrate the state-of-the-art advances and challenges on research and development of RMTs from the perspectives of architecture design, configuration design and optimisation, and system integration and control. In architecture design, semi-open and open architectures based on modular design approach are often selected to allow different modules of the machine to be added and removed. In configuration design and optimisation, operations of reconfiguration processes are analysed and optimised to achieve variety of configurations with the minimum reconfiguration effort. In system integration and control, transfers of motion, energy and data among different modules of the RMT are carried out. The challenges in research on RMTs are also discussed.     

Dynamic DNA Structures

Dynamic DNA structures, a type of DNA construct built using programmable DNA self‐assembly, have the capability to reconfigure their conformations in response to environmental stimulation. A general strategy to design dynamic DNA structures is to integrate reconfigurable elements into conventional static DNA structures that may be assembled from a variety of methods including DNA origami and DNA tiles. Commonly used reconfigurable elements range from strand displacement reactions, special structural motifs, target‐binding DNA aptamers, and base stacking components, to DNA conformational change domains, etc. Morphological changes of dynamic DNA structures may be visualized by imaging techniques or may be translated to other detectable readout signals (e.g., fluorescence). Owing to their programmable capability of recognizing environmental cues with high specificity, dynamic DNA structures embody the epitome of robust and versatile systems that hold great promise in sensing and imaging biological analytes, in delivering molecular cargos, and in building programmable systems that are able to conduct sophisticated tasks.     

3D Printable and Reconfigurable Liquid Crystal Elastomers with Light-Induced Shape Memory via Dynamic Bond Exchange

3D printable and reconfigurable liquid crystal elastomers (LCEs) that reversibly shape-morph when cycled above and below their nematic-to-isotropic transition temperature (T_NI) are created, whose actuated shape can be locked-in via high-temperature UV exposure. By synthesizing LCE-based inks with light-triggerable dynamic bonds, printing can be harnessed to locally program their director alignment and UV light can be used to enable controlled network reconfiguration without requiring an imposed mechanical field. Using this integrated approach, 3D LCEs are constructed in both monolithic and heterogenous layouts that exhibit complex shape changes, and whose transformed shapes could be locked-in on demand.     

An embryonic approach to reliable digital instrumentation based on evolvable hardware

Embryonics encompasses the capability of self-repair and self-replication in systems. This paper presents a technique based on reconfigurable hardware coupled with a novel backpropagation algorithm for reconfiguration, together referred to as evolvable hardware (EHW), for ensuring reliability in digital instrumentation. The backpropagation evolution is much faster than genetic learning techniques. It uses the dynamic restructuring capabilities of EHW to detect faults in digital systems and reconfigures the hardware to repair or adapt to the error in real-time. An example application is presented of a robust BCD to a seven-segment decoder driving a digital display. The results obtained are quite interesting and promise quick and low cost embryonic schemes for reliability in digital instrumentation.