Analysis Of Flexible Manufacturing Systems Research Articles

Parametric transformation of timed weighted marked graphs: applications in optimal resource allocation

Timed weighted marked graphs are a subclass of timed Petri nets that have wide applications in the control and performance analysis of flexible manufacturing systems. Due to the existence of multiplicities (i.e., weights) on edges, the performance analysis and resource optimization of such graphs represent a challenging problem. In this paper, we develop an approach to transform a timed weighted marked graph whose initial marking is not given, into an equivalent parametric timed marked graph where the edges have unitary weights. In order to explore an optimal resource allocation policy for a system, an analytical method is developed for the resource optimization of timed weighted marked graphs by studying an equivalent net. Finally, we apply the proposed method to a flexible manufacturing system and compare the results with a previous heuristic approach. Simulation analysis shows that the developed approach is superior to the heuristic approach.

Transient Analysis of Multiproduct Bernoulli Serial Lines With Setups

Performance analysis of flexible manufacturing systems has received substantial research attention. Most of the studies focus on steady-state behavior. The transient performance, which is critical for system operation, control, and improvement, is less investigated. No analytical method is available to evaluate the transients in flexible lines with unreliable machines, finite buffers, and setup times. In this article, an analytical model is introduced to study the transient performance of multiproduct serial lines with Bernoulli reliability machines and nonnegligible setups during changeovers. To reduce the state-space dimension, an approximation method is introduced to evaluate the performance in two-machine lines, where the sequence of multiple part types in the inventory is approximated by the ratio of product mix. Such an approximation method leads to high precision of production rate estimation. Then, for longer lines, the analysis approach in two-machine lines is used as a building block in an iterative aggregation procedure. Numerical experiments show that the iteration procedure is convergent and results in an acceptable accuracy in performance evaluation. In addition, system properties, such as monotonicity and reversibility, are investigated.

A Time Petri Net With Relaxed Mixed Semantics for Schedulability Analysis of Flexible Manufacturing Systems

Several semantics models are adopted by time Petri nets for different applications. Yet they have some limitations on schedulability analysis of flexible manufacturing systems. The scheduling scope of a strong semantics model is greatly limited because of the impact of strong timing requirements, perhaps keeping some optimal schedules out of the consideration. A weak semantics model cannot guarantee the scheduling timeliness as there lacks strong timing enforcement. A mixed semantics model cannot ensure that independent transitions with overlapping firing interval fire in an interleaving way, thus affecting the search for the optimal schedules. In this paper, we present a relaxed mixed semantics model for time Petri nets to address these problems by redefining the firability rules of transitions. In our model, the firability of a transition is determined by maximal concurrent sets containing the transition. This treatment not only extends the scheduling scope of TPN model greatly while avoiding the generation of invalid schedules, but also solves the problem of concurrent scheduling of independent transitions. A state class method is then proposed to support the verification and analysis of temporal properties. Finally, we apply the proposed model to schedulability analysis of a job shop scheduling problem, and compare the features of four semantics models.

The virtual FMS – an engineering education environment

Abstract The challenge of education related to large technical systems is to provide enough hands-on experience. Virtual models and visualizations make it easier to explain the behavior of those systems. This paper discusses on the development of such a learning environment for engineering education that focuses on planning, operation, and analysis of Flexible Manufacturing Systems (FMS). The aim of the learning environment is to allow the students to achieve the intended learning outcomes mostly with learning by doing. For this purpose, the learning environment is introduced and the individual exercises are described with their teaching and learning activities. This kind of learning by doing in an environment, which is similar to environments in manufacturing companies, enhance the learning results and serve the needs of the industrial companies recruiting the students.

Simulation Tool for Assessing the Performance of a Flexible Manufacturing System

The flexible manufacturing system (FMS) is as complex whole, raises concerns regarding the configuration and dimensioning, as well as on the conditions for implementation. The scientific researches in this paper, are directed towards the study and analysis of flexible manufacturing systems, in order to know their behaviour and performances as well, and if possible, even before their physical realization, and to establish the scientific basis for sizing, configuration and simulation patterns of flexile manufacturing systems. The ARENA simulation software can describe the complex interactions between resources and processes that take place within a FMS, a system of discrete events. In the simulation phase, evaluation of performance criteria allows the introduction of planning strategies in the use of system resources. After developing these models the verification and validation of the models, confirms their validity. The researches will be also extended in the domain of flexible manufacturing systems management and control in real and virtual environment.

Simulation Modelling and Analysis of Flexible Manufacturing Systems with flexsim software

This paper deals with a simulation study to investigate how to optimize manufacturing time in Flexible Manufacturing Systems. The combination of flexible machines and flexible operational sequences simulation software are used to obtain a full routing flexibility in FMS. Flexibility in manufacturing systems offers reducing waiting time, decreasing cost, and increasing efficiency. This paper entails an efficient real-time flexible routing strategy, to maximize the system throughput by balancing the workload and minimize the system unbalance. Full routing flexibility provides significant enhancement in the system improvement and gives how a routing control policies influence condition of a system.

Introducing Flexibility to Complex, Resilient Socio-Ecological Systems: A Comparative Analysis of Economics, Flexible Manufacturing Systems, Evolutionary Biology, and Supply Chain Management

In this paper, a framework incorporating flexibility as a characteristic is proposed for designing complex, resilient socio-ecological systems. In an interconnected complex system, flexibility allows prompt deployment of resources where they are needed and is crucial for both innovation and robustness. A comparative analysis of flexible manufacturing systems, economics, evolutionary biology, and supply chain management is conducted to identify the most important characteristics of flexibility. Evolutionary biology emphasises overlapping functions and multi-functionality, which allow a system with structurally different elements to perform the same function, enhancing resilience. In economics, marginal cost and marginal expected profit are factors that are considered to be important in incorporating flexibility while making changes to the system. In flexible manufacturing systems, the size of choice sets is important in creating flexibility, as initial actions preserve more options for future actions that will enhance resilience. Given the dynamic nature of flexibility, identifying the characteristics that can lead to flexibility will introduce a crucial dimension to designing resilient and sustainable socio-ecological systems with a long-term perspective in mind.

Analysis of Flexible Manufacturing System using Petri Nets to design a Deadlock Prevention Policy

Analysis of Flexible Manufacturing System using Petri Nets to design a Deadlock Prevention Policy

Application of AHP in the Analysis of Flexible Manufacturing System

Application of AHP in the Analysis of Flexible Manufacturing System

Characteristics Analysis of Flexible Manufacturing Systems

For the rigid automatic line, although its production efficiency is high, but the flexible is less in the machining process, the machine and the assembly line need be shut down to adjust or replace for machine tools, jigs, tools, and tooling equipment, etc. When the work pieces for the machining is changed. It caused a heavy workload, wasting a lot of time. Flexible Manufacturing Systems consisted of unified control system, material handling system and a set of digital control processing equipment; it is the automation machinery manufacturing system to adapt the processing object transform. It has become one of the important means of manufacturing industry to obtain the advantages of market competitiveness. This paper gives the composition, algorithm and application of learning system concept, composition, and classification, characteristics of the flexible manufacturing system, the development overview and its application are induced in this paper.

Integrated definition modeling and Taguchi analysis of flexible manufacturing systems: aircraft industry application

In this paper, flexible manufacturing systems (FMS) are studied. Firstly, an FMS design approach is proposed using integrated definition for function methodology. A systematic layout design and performance evaluation scheme is presented and detailed using this modeling framework. Then, the proposed approach is carried out with a case study from an aircraft industry to convert an existing traditional production system to FMS. To improve the system performance, a simulation-based method with Taguchi approach consisting of multiproducts is utilized. The objective is to find the machine and the product mix that achieves the maximum utilization while minimizing the cycle time. FMS system performance has been greatly improved by determining the most advantageous level of system components. It has also shown that FMS is a practicable production system in aircraft industry.

Performance Analysis of Flexible Manufacturing Systems with a Single Discrete Material-Handling Device

We present an analytical model for performance prediction of flexible manufacturing systems (FMSs) with a single discrete material-handling device (MHD). This configuration of FMS is significant for many reasons: it is commonly found in industry, it simplifies material-handling control, it is amenable to analytical modeling, and it forms a building block for more complex systems. Standard queueing models are inadequate to analyze this configuration because of the need to take into consideration many nontrivial issues such as state-dependent routing, interference from the MHD, and the analysis of the MHD. To account for state-dependent routing, we develop an iterative method that is built around mean value analysis. To analyze the MHD interference, we use two queueing network models. In the first, we ignore queueing at the MHD but model the interference from the MHD by inflating the station service times. The second network models the queueing for the MHD and estimates the blocking (inflation) times needed for the first model. By iterating between the two networks, we are able to predict the performance of this configuration of FMS. Our analytical estimates are validated against discrete event simulation and shown to be quite accurate for initial system design.

An experimental analysis of steady state convergence in simple queueing systems: Implications for flexible manufacturing system models

Queueing models are widely used for performance analysis of Flexible Manufacturing Systems (FMS). Most studies are done under steady state assumptions. The inherent flexibility of FMS in terms of input, volume, and mix makes such an assumption hard to justify. In this paper, we investigate the convergence rate to steady state in simple queueing models that constitute the basic building blocks of more complex FMS models. The study reveals that steady-state conditions are not achieved during the execution of batches of moderate size. We therefore conclude that although equilibrium models are appropriate for studying long-term planning problems, for the operational control of FMSs, it is highly desirable to study the transient behaviour of the system. On a broader scope, our investigation also shows that steady-state assumptions used in the analysis of any inherently transient system should be carefully validated.

Analytical modeling and analysis of flexible manufacturing systems considering system component failure/repair rates

An effective analytical model is developed to investigate the performance of an FMS with given system component failure/repair rates. System performance is measured analytically by projecting average part flow time, which is achieved by first conceptually transforming the FMS into multiple nonhomogeneous transfer lines. The efficiency and average part flow time of each transfer line are approximated by disaggregation and homogenization transformations and the decomposition technique. An aggregation of performance of all transfer lines predicts FMS performance. The small percentage difference between the average part flow time derived from an analytical model and from a simulation model indicates that the analytical model is an effective tool.

Analysis of flexible manufacturing systems with distinct repeated visits: DrQ

This article examines the performance effects caused by repeated part visits at the workstations of a flexible manufacturing system (FMS). Such repeated part visits to the same workstations are commonly associated with fixture changes for machining complex parts, reclamping, and remounting or reorienting them. Since each of the repeated visits to a workstation may require different processing requirements, the resulting queueing network does not have a product form solution. We therefore develop an approximate mean value analysis model for performance evaluation of an FMS that may produce multiple part types with distinct repeated visits. We provide numerical examples and validate the accuracy of our solution algorithm against simulation. These examples show that the proposed model produces accurate throughput and utilization predictions with minimal computational efforts. These examples reveal that increasing the total pallet population may result in a reduction of the aggregate throughput, and that the FMS's performance could be more sensitive to the mix of pallets and part routes than to the total number of pallets. Our model will be of use, in particular, when managers wish to control individual operations (e.g., to adjust individual operation times to achieve economic savings in tool wear and breakage costs) or to investigate the performance implications of route changes due to alternate assignments of particular manufacturing tasks to certain workstations.

XPN-FMS: A CAD tool for FMS modeling, analysis, animation, and simulation using Petri nets and X window

We propose a CAD tool, XPN-FMS, which is primarily based on a unique Petri net (PN) synthesis method, called the knitting technique, developed by the authors. Petri net theory has been applied to specification, validation, performance analysis, control code generation, and simulation for manufacturing systems. The analysis of flexible manufacturing systems (FMSs) based on PNs suffers from the complexity problem of reachability analysis (Peterson, 1981). CAD tools are urgently needed. There is no existing CAD tool for FMSs as comprehensive as XPN-FMS, in the sense that the latter integrates the functions of drawing, analysis, reduction (Chao and Wang, 1992; Murata and Koh, 1980), synthesis, property queries, and animation of FMS operations in one software package. Using the X window graphical interface and animation, XPN-FMS makes the modeling and analysis of an FMS visualizable and easy to understand and manipulate. It lets a user draw the factory layout of an FMS on the screen of a monitor using the supplied tools. A corresponding PN model can also be drawn on the monitor screen. XPN-FMS can animate and simulate the overall operating process of the FMS. It is useful for FMS specification, validation, and exploration of different design alternatives, status monitoring, and control. Using XPN-FMS with various inputs and comparing the resulting outputs, the user can determine how to improve efficiency, reduce cost, and pinpoint bottlenecks. For the PN models of FMSs that are decision free, we extend the theory and algorithm of a unique matrix-based method (Chao and Wang, 1993b) to search for subcritical loops (including types A and B) and to support scheduling and dealing with transition periods. XPN-FMS implements this extended method to find the minimum cycle time, critical loop, subcritical loops, next critical loop, and scheduling ranges to avoid the transient period for static scheduling. This is implemented in XPN-FMS for the input sequence control.

Robust design and optimization of material handling in an FMS

Although a significant amount of simulation research has been carried out for design and analysis of flexible manufacturing systems (FMS), it does not provide optimal solutions. In this research, we employ two optimum-seeking methods to design and optimize a manufacturing system. The first method is a Taguchi approach, which uses robust design concept to reduce the output variation. The second method is the response surface methodology (RSM), which combines mathematical and statistical techniques to study the geography of the response surface. The results show that throughput of a selected FMS system can be maximized when both methods are employed.

On using abstract models for analysis of flexible manufacturing systems

Abstract The modelling and analysis of Flexible Manufacturing Systems (FMS) has been approached through a variety of methodologies, which diverge considerably in their ability to represent and analyse complex FMS features. This paper broadly classifies the chief approaches, and evaluates them against certain prescriptions. Petri Nets and their extensions score highly on the evaluation criteria. A modelling approach is presented based on Conditional Predicate/Transition Nets (CPrTN), which extend the modelling power of Predicate/Transition Nets. CPrTN provide formal, concise and graphical models, eminently suited for modelling the often complex dynamic interactions in an FMS.

A petri net-based simulation tool for the design and analysis of flexible manufacturing systems : Dong-Soon Yim and Thomas A. Barta, pp. 251–261

A petri net-based simulation tool for the design and analysis of flexible manufacturing systems : Dong-Soon Yim and Thomas A. Barta, pp. 251–261

A Petri net-based simulation tool for the design and analysis of flexible manufacturing systems

Abstract Simulation is an invaluable tool in designing and analyzing manufacturing systems. A Petri net-based simulation tool is presented to aid simulation projects in manufacturing, including flexible manufacturing systems (FMSs). Three models are developed—an object model, Petri net model, and control model. While hardware components of FMSs are modeled by Petri net objects, control functions are separately modeled and integrated with a Petri net model to resolve conflicts occurring in Petri net execution. Facilities of the developed tool are presented, and a modeling procedure with the tool is illustrated via a case study.