A mixed dispatching rule approach in FMS scheduling

Short-term scheduling in flexible manufacturing systems (FMSs) is a difficult problem because of the complexities and dynamic behavior of FMSs. To solve this problem, a dispatching rule approach is widely used. In this approach, however, a single dispatching rule is usually assigned for all machines in a system during a given scheduling interval. In this paper, a mixed dispatching rule which can assign a different dispatching rule for each machine is proposed. A search algorithm which selects an appropriate mixed dispatching rule using predictions based on discrete event simulation is developed for this approach. The search algorithm for the mixed dispatching rule is described in detail. The effectiveness (in meeting performance criteria) of the mixed dispatching rule and the efficiency of the search algorithm relative to exhaustive search (complete enumeration) is demonstrated on an FMS model. The mixed dispatching rule approach performs up to 15.9% better than the conventional approach, and is 4% better on average. The statistical significance of the results is dicussed.     

An algorithm for deadlock avoidance in an AGV System

In this paper, a simple and easily adaptable deadlock avoidance algorithm for an automated guided vehicle (AGV) system is presented. This algorithm uses the graph-theoretic approach. Unlike Petri-net-based methods, which are complex and static, it is easy to modify the existing model as the configuration of the system changes. Therefore, it is suitable for the AGV system in a flexible manufacturing system (FMS) and a retail or postal distribution center. Moreover, because it is very simple, it is appropriate for real-time control mechanisms.This paper consists of two parts: the first part presents an AGV deadlock avoidance algorithm that uses the graph-theoretic approach, and the second suggests appropriate routing strategies based on the proposed algorithm. The results show that this deadlock avoidance algorithm can be modified easily whenever the configuration of an FMS changes and provide high-performance on the deadlock avoidance. Finally, experimental results that confirm the validity of this approach are provided.     

A combined additive manufacturing and micro-syringe deposition technique for realization of bio-ceramic structures with micro-scale channels

This article presents a novel rapid layered manufacturing approach based on a combined additive manufacturing (AM) process and a UV-based micro-syringe deposition (μSD) technique to be used in the fabrication of bio-ceramic structures with controlled micro-sized channels for bone and osteochondral tissue regeneration. In the proposed rapid manufacturing method, micro-scale sacrificial photopolymer networks are integrated within the manufactured part by depositing the photopolymer on selected bio-ceramic powder layers using an injection system. This AM–μSD method along with a post-processing protocol can potentially overcome current limitations of traditional powder-based AM approaches that are restricted in terms of complexity of internal architecture and feature size. For bone or osteochondral repair applications, the material system composed of the bio-ceramic and sacrificial photopolymer, along with the post-processing protocol, must ensure that the final implants are free from manufacturing residuals that could trigger an immune response post-implantation. In this study, calcium polyphosphate bio-ceramic was used as the substrate material based on prior art, polyvinyl alcohol solution was used as the powder binding agent, and ethoxylated (10 bisphenol A diacrylate) photopolymer solution was used as the sacrificial photopolymer element. Material characterization suggests that the proposed material system along with heat treatment protocol is suitable for the targeted applications where micro-scale channels within the implant are produced by AM–μSD.     

An algorithm for deadlock avoidance in an AGV System

In this paper, a simple and easily adaptable deadlock avoidance algorithm for an automated guided vehicle (AGV) system is presented. This algorithm uses the graph-theoretic approach. Unlike Petri-net-based methods, which are complex and static, it is easy to modify the existing model as the configuration of the system changes. Therefore, it is suitable for the AGV system in a flexible manufacturing system (FMS) and a retail or postal distribution center. Moreover, because it is very simple, it is appropriate for real-time control mechanisms.This paper consists of two parts: the first part presents an AGV deadlock avoidance algorithm that uses the graph-theoretic approach, and the second suggests appropriate routing strategies based on the proposed algorithm. The results show that this deadlock avoidance algorithm can be modified easily whenever the configuration of an FMS changes and provide high-performance on the deadlock avoidance. Finally, experimental results that confirm the validity of this approach are provided.     

人机协同制造系统可靠性试验与评估

人机协同制造系统可靠性对系统的运行具有重要影响,在建立人机协同制造系统可靠性模型基础上,提出人机协同制造系统可靠性试验与评估方法.利用某人机协同制造系统可靠性增长试验中积累的可靠性试验数据,估算出系统目前的可靠性指标,研究结果表明,该方法在系统可靠性分析中合理可行.     

Information-Based Dynamic Manufacturing System Scheduling

Information about the state of the system is of paramount importance in determining the dynamics underlying manufacturing systems. In this paper, we present an adaptive scheduling policy for dynamic manufacturing system scheduling using information obtained from snapshots of the system at various points in time. Specifically, the framework presented allows for information-based dynamic scheduling where information collected about the system is used to (1) adjust appropriate parameters in the system and (2) search or optimize using genetic algorithms. The main feature of this policy is that it tailors the dispatching rule to be used at a given point in time to the prevailing state of the system. Experimental studies indicate the superiority of the suggested approach over the alternative approach involving the repeated application of a single dispatching rule for randomly generated test problems as well as a real system. In pa ticular, its relative performance improves further when there are frequent disruptions and when disruptions are caused by the introduction of tight due date jobs and machine breakdown—two of the most common sources of disruption in most manufacturing systems. From an operational perspective, the most important characteristics of the pattern-directed scheduling approach are its ability to incorporate the idiosyncratic characteristics of the given system into the dispatching rule selection process and its ability to refine itself incrementally on a continual basis by taking new system parameters into account.     

零件轮廓测量机安全监测系统的设计

为适应现代先进制造业质量检测自动化的需要,研究开发能够在线非接触、高精度自动检测的智能三坐标测量机已经成为制造业发展的必然趋势,其中机器视觉检测技术的应用为实现复杂自由曲面的自动化检测提供了技术支持。介绍了零件轮廓测量机的工作原理,分析了回转工作台和偏心调整机构在回转体零件测量系统中的作用。采用合理的图像处理技术,完成了包括测量工位上异常物体的检测、工件类型识别和工件位置检测等功能在内的图像识别系统的设计。     

Maintenance Integration in Manufacturing Systems: From the Modeling Tool to Evaluation

In manufacturing systems, wear-out and eventual failure are unavoidable. However, to reduce the rate of their occurrence and to prolong the life of equipment or the capacity for extended productive use of the equipment under the necessary technological functioning and servicing, maintenance can be performed. For large manufacturing systems, maintenance integration involves a particular development concerned with both complexity models and computing time. This paper presents an effective way of modeling complex manufacturing systems through hierarchical and modular analysis by using stochastic Petri nets and Markov chains. In the proposed approach, the integration of maintenance policies in a manufacturing system is facilitated by the development of a generic model. With this generic modeling, the user doesn't need to code the strategies but only to instantiate the generic model with the structure of the manufacturing system. This method allows various maintenance strategies to be coded in the generic model with the aim of studying their influence on system dependability and performance.     

An integrated object-oriented approach for design and analysis of an agile manufacturing control system

The agile manufacturing paradigm has emerged as an important concept in the development of manufacturing systems. The control software, developed based on the object-oriented technology, leads to reusability, reconfigurability, and scalability; and the agility of a manufacturing control system can be achieved. In this research, an efficient and systematic methodology for developing an object-oriented agile manufacturing control system is proposed. The proposed development process is divided into four stages: functional analysis, static structural analysis, behavior analysis and verification, and system implementation. The Integration Definition for Function Modeling (IDEF0), Object-Oriented Petri Net (OPN), and Unified Modeling Language (UML) are integrated into the corresponding stages based on their characteristics. In order to develop the system rapidly and efficiently, the transformation rules between the IDEF0 and OPN, and between the OPN and sequence diagram are conducted. In addition, the attributes and operations for each object are also defined directly from the OPN model. The result of the integrated IDEF0/OPN/UML systematically leads to object-oriented control software design for manufacturing systems. Finally, an assembly and packaging system is given to illustrate how the integrated object-oriented approach is implemented for developing the manufacturing control system.     

Modelling and Evaluation of Manufacturing Systems Using Dedicated Petri Nets

The design of a manufacturing system requires modelling and performance evaluation techniques. To support this process, a modelling method based on Petri nets is proposed in this paper. A new class of coloured Petri nets is introduced, which is well suited to the modelling of manufacturing systems. Using this net class, the structure and the work plans of a manufacturing system can both be modelled separately. A library of model templates helps to create large models. The different model parts are merged automatically to create a complete model of the manufacturing system. Measures of interest can be obtained from the model by numerical analysis or simulation, showing its performance and dependability. The usefulness of the approach is shown by applying the proposed techniques to a real-life manufacturing system.     

Performance analysis of network and database transactions flow in a CIM system

A Petri net-based integrated model for the performance analysis of network and database transactions, generated by manufacturing clients for computer resources which are acting as the servers, is discussed. A Petri net-based multifaceted integrated modelling (PNBMIM) approach is described to investigate relevant system integration issues between the logical and physical access of information in the manufacturing system. The PNBMIM approach proposes an integrated conceptual framework for modelling and performance (both structural and behavioural) analysis of data and communication flow. Also, this framework will provide some answers to the impact of relative time-scales on the coupling and de-coupling of the various levels of a computer integrated manufacturing system, and identify the time-scales where integration becomes important. This work recognizes that the productivity of a group of machines is influenced by the dynamics of the computer resources. An example illustrating the application of the PNBMIM framework to two transfer lines is discussed.     

Performance Analysis of Intelligent Robust Facility Layout Design

Design of a robust production facility layout with minimum handling cost (MHC) presents an appropriate approach to tackle facility layout problems in a dynamic volatile environment, in which product demands randomly change in each planning period. The objective of the design is to find the robust facility layout with minimum total material handling cost over the entire multi-period planning horizon. This paper proposes a new mathematical model for designing robust machine layout in the stochastic dynamic environment of manufacturing systems using quadratic assignment problem (QAP) formulation. In this investigation, product demands are assumed to be normally distributed random variables with known expected value, variance, and covariance that randomly change from period to period. The proposed model was verified and validated using randomly generated numerical data and benchmark examples. The effect of dependent product demands and varying interest rate on the total cost function of the proposed model has also been investigated. Sensitivity analysis on the proposed model has been performed. Dynamic programming and simulated annealing optimization algorithms were used in solving the modeled example problems.     

Makespan minimization for m-machine permutation flowshop scheduling problem with learning considerations

Increased complexity of current manufacturing systems together with dynamic conditions and permanent demands for flexible and robust functionality makes their management and control very difficult and challenging. Workflow simulation is an effective approach to investigate dynamic workflow scheduling policies and evaluate the overall manufacturing system performance. The results attained in simulation model can give directions on how to maximize system output when selecting an appropriate scheduling practice for a real system. In this paper, we investigate the abilities of multi-agent systems in combination with dynamic dispatching rules and failure handling mechanisms to manage dynamic environment conditions (such as machine failures) for systems in the production automation domain. We measure system robustness by systematically assessing the total system performance (e.g., number of finished products) in a number of representative test cases. We use an agent-based simulation environment, MAST, which has been validated with real-world hardware to strengthen the external validity of the simulation results. We investigated the performance of a re-scheduling component which uses four different policies that define how to adjust the system schedule in case of machine disturbances/failures. In the context of the empirical study the Complete Rerouting re-scheduling policy outperformed all other policies.     

基于数据包络分析的网络化制造联盟企业制造资源配置评价研究

针对网络化制造联盟企业的制造资源配置评价问题,建立了成本收益数据包络分析数学模型,提出了以此为核心的制造资源配置评价方法。该评价方法基于数据包络分析的基本思想,将制造资源配置评价问题映射为制造资源配置的成本收益分析问题,应用完全成本分析和作业成本分析方法,建立网络化制造联盟企业制造资源的自营配置成本、外包配置成本和制造资源配置的收益价值模型。在此基础上,建立制造资源配置评价的成本收益数据包络分析模型,并提出资源的优化配置策略。最后,以实际运营的新产品快速开发网络化服务平台为例,验证了分析模型的有效性和实用性。     

A multi-stage methodology for virtual cell formation oriented agile manufacturing

In recent years, as an emerging concept in industry, agile manufacturing has attracted considerable attention, combining virtual manufacturing cells to construct new manufacturing systems to respond to the changing market needs, especially in nonlinear processes. In this paper, a multi-stage cell formation methodology, which can help select appropriate resources and form the VCs, is presented. First, appropriate resources for completing production tasks are selected by a LP model considering the available capacity and the costs. In order to form VC in a logical mode, parts having alternative product process routings as multi-functional machines are analyzed by a resource element approach. Furthermore, some routing-based heuristic rules are introduced to optimize the candidate VCs in the form of resource elements. Finally a case study is used to illustrate the detailed formation methodology.     

Development of the supply chain oriented quality assurance system for aerospace manufacturing SMEs and its implementation perspectives

Aerospace manufacturing SMEs are continuously facing the challenge on managing their supply chain and complying with the aerospace manufacturing quality standard requirement due to their lack of resources and the nature of business. In this paper, the ERP system based approach is presented to quality control and assurance work in light of seamless integration of in-process production data and information internally and therefore managing suppliers more effectively and efficiently. The Aerospace Manufacturing Quality Assurance Standard (BS/EN9100) is one of the most recognised and essential protocols for developing the industry-operated-and-driven quality assurance systems. The research investigates using the ERP based system as an enabler to implement BS/EN9100 quality management system at manufacturing SMEs and the associated implementation and application perspectives. An application case study on a manufacturing SME is presented by using the SAP based implementation, which helps further evaluate and validate the approach and application system development.     

Production Scheduling and Cell Formation for Virtual Cellular Manufacturing Systems

In this paper, an approach using the concept of genetic algorithms is proposed as a powerful but simple means of scheduling the manufacturing operations of a virtual cellular manufacturing system (VCMS). A mathematical model is developed to describe the characteristics of a VCMS, which includes the constraints related to the delivery due dates of the various products and the maximum capacities of the manufacturing resources. The objectives are to set up virtual manufacturing cells and to formulate feasible production schedules for all manufacturing operations, in order to minimise the total material and component travelling distance incurred in manufacturing the products. A new genetic based scheduling algorithm is proposed as an optimisation tool to determine the solution. The proposed algorithm differs from the conventional genetic algorithms in that the populations of the candidate solutions consist of individuals from various age-groups, and each individual is incorporated with an age attribute to enable its birth and survival rates to be governed by predefined ageing patterns. By generating the evolution of the populations with the genetic operators of selection, crossover and mutation, the proposed approach provides excellent results by maintaining a better balance between the exploitation and the exploration of the solution space, and thus improves the computational speed and the solution quality. The condition ensuring stable search performance is also derived. The superiority of the proposed algorithm is illustrated by solving the production-scheduling and cell-formation problems for a virtual cellular manufacturing system, and the results are compared with those obtained by using a conventional optimisation technique.     

Optimization and implementation of cellular manufacturing system in a pump industry using three cell formation algorithms

In recent years cellular manufacturing has become an effective tool for improving productivity. Attainment of full benefits of cellular manufacturing depends firstly on the design of the machine cells and part families and secondly on the method of operation which take full advantages of cell properties. Inappropriate methods of loading and scheduling can even lead to the failure of cellular manufacturing systems (CMS), however efficiently the cell is designed. This paper examines three array-based clustering algorithms, namely rank order clustering (ROC), rank order clustering-2 (ROC2) and direct clustering analysis (DCA) for manufacturing cell formation, with a real-life example to demonstrate the effectiveness of various clustering algorithms. The machine cell formation methods considered in this comparative and evaluative study belongs to the cluster formation approach of solving the MCF problem. The most effective method is selected and used to build the cellular manufacturing system. The comparison and evaluation are performed using four published performance measures and compares the improvements with the existing conventional system and the cellular manufacturing system. The above algorithms were written in the C++ language on an Intel/Pentium III-PC-compatible system.