Reuse in a simulation environment for flexible manufacturing systems

A flexible manufacturing system (FMS) is a highly automated, complex system. Simulation is a well-proven method to design or analyze an FMS. Deployment of a radio frequency identification (RFID) system in FMS produces large volumes of RFID data streams, which provide valuable information to improve the operation of FMS. Different frameworks are presented in this paper regarding the use of RFID data streams in an FMS simulation. Simulations are performed with AutoMod software. Related technical details are also presented. The paper’s structure is complied as the following steps: step 1, the introduction of AMHS, FMS and AutoMod; step 2, FMS simulation using AutoMod software; step 3, simulation frameworks driven by RFID data streams; step 4, conclusion.

Flexible manufacturing has been amazingly developed and now becomes one of the leading manufacturing facilities in all the industrial nations. Flexible manufacturing can be classified into several basic system configurations, and of these Flexible Manufacturing Cell (FMC) is dominant, and even the large-sized Flexible Manufacturing System (FMS) is to be in reality by integrating a group of FMCs, i.e. FMC-integrated system of modular type. In consequence, we need now the design methodology for flexible manufacturing, extremely the standardisation of basic FMCs. Within standardised FMC context, a facing engineering problem is to apply the graph theory to the description of FMC, so that the similarity evaluation for FMC can be carried out. On the strength of the similarity evaluation, it is possible to determine a group of standardised FMCs, which can facilitate the system design for flexible manufacturing as core modules to greater extent.

This paper describes the ways of using program tools for design and simulation of flexible manufacturing systems (FMS) for the purpose of teaching the undergraduate course Flexible Manufacturing Systems. The concept of the course is based on the synergism of theoretical knowledge and practical hands-on experience gained by studying numerous problem cases, using common tools for description of FMS (Petri nets, max-plus algebra and matrix modeling) and by working with more specialized program tools for FMS design and simulation. An emphasis is given to the description o the program tool FlexMan that enables elegant setting of an FMS configuration, supports automatic generation of a matrix-based FMS description and consequently, enables effective off-site design and simulation of the FMS by using virtual reality models and Internet-related technologies.

The paper deals with the problem of the development of 3D graphic representation and simulation of flexible manufacturing systems. A 3D graphic model of a plant can improve the work performed in different control processes during the system life cycle, such as commissioning, monitoring and maintenance. These aspects become more relevant dealing with complex systems. Furthermore, for flexible manufacturing systems, mechanisms to manage the system modularity in the development of the 3D graphic representations are needed. A key factor which is bringing visibility to 3D techniques is the technical improvement of personal computer allowing to have relatively cheap, high graphical performances. Consequently, during last few years, several 3D visualization tools appeared on the marked. Within the paper, two existing simulation tools, 3D create and day dream daemon, are analyzed and compared. Both, have successively been used for the development of a simulation environment for the validation of control functions of a real manufacturing system.

During the last decade (from the late 1970s to the beginning of the 1990s), manufacturing systems have significantly changed. Their function and performance have altered in a period of rapid development, mainly as a result of the application of the techniques of computer science. The new systems are termed either flexible manufacturing systems (FMS) or computer- integrated manufacturing (CIM). The advance of flexible manufacturing and its related technologies has been accompanied by a number of related developments, such as flexible manufacturing of a global network type, CIM incorporating personnel functions, skill-based manufacturing, and compact flexible manufacturing cells (FMC). These all have notable influences on the system configuration and operational technologies of flexible manufacturing: perhaps as a result, there is some confusion about their terminology. A number of differing nomenclatures are used (such as FMC, FMS, flexible or factory automation (FA), CIM and enterprise automation (EA), for the same fundamental technology.

Flexible Manufacturing Systems (FMS) provide capabilities to accommodate flexibility requirements in production. Such system due to the levels of flexibility are complex to reconfigure optimally. Simulation is one of the tools that provide a platform for supporting the FMS reconfiguration without breaking optimal production set-up. For the simulation to be successful it is important to appropriately design the simulated environment as well as provide quality data inputs. As FMS are usually driven by production line controllers (PLC), the behaviour of elements in the system can be difficult to be fully understood. The quality of data fed in to the simulation affects the quality of outputs which in consequence translates to the trust that the simulation is reliable source of analysis. This paper presents the approach of data collection from the shop floor aiding FMS simulation in scenarios where it is difficult to understand the system behaviour. Also, case study of a manual handling robot in the FMS is presented to demonstrate obtaining quality data from the production shop floor.

A flexible manufacturing cell (FMC) is part of a flexible manufacturing system (FMS). In general, a FMC consists of versatile workstations and storage buffers connected by a versatile material handling system. Owing to its versatile configurations and material routeing alternatives, effective modelling and control of the FMC is a complex and challenging problem. In order to resolve these difficulties, it is desired to establish a set of specifications for the FMC, then to develop a suitable model to analyse and control the performance of the FMC. Since the cell control is distributed in nature, the cell controller specifications are established in terms of cell functionality, software, hardware, and environment aspects. On the basis of the cell controller specification, a coloured timed Petri net (CTPN) is developed for modelling and control of the FMC. A cell controller including CNC controller, robot controller will be developed on the basis of the CTPN model. Finally, a FMC example is given to illustra...

This paper reports on a development of feature-focused dynamic routing policy and its evaluation in a flexible manufacturing systems (FMS) simulation framework. The dynamic policy is based on an integrative methodology in which process planning system IMPlanner is integrated with FMS simulation module. IMPlanner’s rule-based system process selection system performs knowledge-intensive task of generating alternative processing options for each feature for parts in production plan. Generated alternative routings (process plan network) for each part are utilized in the FMS simulation module such that routing decision in FMS are made on periodic intervals by considering alternative processes for each feature and making decision based on the current system status and performance. The proposed framework has been evaluated in an experimental FMS simulation module, implemented in Arena, in which two performance criteria, machine utilization and WIP, were used to make routing decisions. The feature-focused approach is compared with traditional static decision-making, and its improved performance is demonstrated.

Flexible manufacturing systems: Present development and trends

The authors discuss the modeling of flexible manufacturing systems (FMSs) under uncertainty and evaluate a rule base for online scheduling. To represent uncertain events in an FMS, such as failure of machine tools, repair time, and processing time, they develop continuous-time and discrete-time stochastic Petri nets with hierarchical structures for constructing the FMS model. For obtaining an efficient schedule for the FMS with an online real-time basis, they construct a rule base and evaluate its performance using the FMS simulation system proposed. >

An FMS is a typical real-time concurrent system composed of a number of computer-controlled machine tools, automated material handling and storage systems that operate as an integrated system under the control of host computer(s). The growing demand for higher performance and flexibility in these systems and the interlocking factors of concurrency, deadline-driven activities, and real-time decision making pose a significant challenge to FMS design, especially in terms of control and scheduling. A formal engineering approach that helps handle the complexity and dynamics of FMS modeling, design and analysis is needed. A real-time architectural specification (RAS) model and its application in the modeling of flexible manufacturing system (FMS) are presented. RAS combines mature operational and descriptive formal methods, in particular time Petri nets (TPN) and real-time computational tree logic (RTCTL), to form an integrated system model for architectural specification and analysis of real-time concurrent systems such as FMS. The contribution of RAS is twofold: First, it provides a formal system to systematically maintain a strong correlation between (real-time) requirements and design and to verify the conformance of the design to the requirements, which helps enhance traceability and thus to help us to achieve high assurance in design. Second, it offers better scalability in modeling and analysis, which provides an effective way to deal with complexity in the application of formal methods. These two features together make RAS a suitable model for the design of FMS.

SummaryIncreasing pressures from a variety of directives and standards have caused manufacturing enterprises to consider and implement energy assessment and energy performance goals—to improve both their economic and their environmental performance. Flexible manufacturing systems (FMSs) pose a challenge for energy management because of their complexity and the difficulty of data collection. FMSs allow manufacturers to adjust to customers’ requirements and meet changing demands, which makes it possible for manufacturers to respond quickly to the market. To address this challenge, a practical energy model for machining systems based on colored timed Petri nets (CTPNs) is proposed. In this article, the energy consumption of FMS are first analyzed. Then, an energy model of FMSs based on CTPNs is proposed in which the uncertainty of task assignment and volatility of operation time are treated by Petri net (PN) functions so that data on the consumption of FMSs can be collected automatically. Finally, through the case study of an FMS with two jobs, the proposed energy model is simulated and the simulation results with colored PN tools are shown to be significant in practice.

A class of Petri nets, called extended Petri nets, with multiple types of places, multiple classes of tokens and multiple arcs is proposed. It is utilized for the hierarchical modeling of flexible manufacturing systems, ensuring a priori that the extended Petri net system model obtained is live, bounded, consistent and error free. The proposed method views the operation of the flexible manufacturing system as a process that is decomposed into operations with specified precedence relations. For each operation the required resources are identified, and on the basis of these requirements the overall system is decomposed into a set of finite subsystems. The operation of each subsystem is modeled as an event graph representing a single resource activity cycle. The extended Petri net system model is synthesized from these component nets using certain synthesis rules. A software package has been developed to simulate the execution of the model obtained. >

A flexible manufacturing cell with vision has been provided with a modular control system based on microcomputers and local area network. The development tool, the shop floor control software, with its basic architecture is overviewed. The control system implementation is presented including the corresponding control modules. An expert routine and scheduling system using rule based simulation is presented. The pilot system described is used to demonstrate flexible manufacturing systems (FMS) technology. It can also be used as a test bed when developing different control methods and algorithms to reach an optimal behaviour of FMS. The current development efforts are concentrated on refining the knowledge based methods to increase the system flexibility and to respond better to various disturbances in the production. >

The possibilities of efficiency increse of working positions (WP) servicing by industrial robots (IR) in mechano-assembly Flexible Manufacturing Systems (FMS) by the workparts intermediate storage places (ISP) usage in Flexible Manufacturing Cells (FMC) are considered. The possible variants of WP service strategies in FMC with one-placed ISP usage are considered, the formal description of service strategies are given. The possible variant of classification of the WP service strategies by IR is proposed. The actuality of computer-aided search of optimal equipment service strategies in conditions of their multivariaty is determined.