Timed Place Petri Net Model Research Articles

IMPROVING PROCESS QUALITY BY NEW LEAN SIX SIGMA METHODOLOGY FOR REVAMPING ONLINE PRODUCTION LINE TRAINING

Factories of today are stuck in severe crisis, so continually striving to improve process quality to reduce both time and costs and add more control procedures to processes. Lean Six Sigma (LSS) derives from Lean thinking and mathematical use of sigma in statistics as a standard deviation for measuring variability; using DMAIC and process mapping to reduce process variation. The LSS process pervades all business aspects such as management, design, production and customer satisfaction. The chronic problems have a solution in the new LSS using timed place Petri net (TPPN), which is a graphical tool used to control and model functional, information, dynamic behavior and decisions aspects of the interrelationship between processes to understand where and how improvements might be made. So, it help in eliminating the causes of problems that absorb resources and create no value to satisfy customer and commensurate with his needs to reduce the discrepancies between actual and planned. Value stream mapping (VSM) is LSS tool used to map the current state and to identify source of waste to eliminate, and map the future state. To quantify the benefits gained from using the new LSS tool in the value stream mapping, a TPPN model was developed to provide the VSM with online data, to get a dynamic VSM which make a continuous system control. This work addresses the application of LSS concepts using TPPN to the continuous production processes sector with a focus on the ceramic industry.

Modeling and Simulation of Dynamic Alliance Task Scheduling

Considering the characteristics of dynamic alliance task scheduling, timed place Petri-net (TPPN)-based approach is proposed to model the task scheduling. On the basis of formal definition and transition rules of the TPPN, dynamic alliance manufacturing types are classified, and the TPPN model of each kind of manufacturing is provided. Then through analyzing time difference of each task, critical path in TPPN model is solved. Finally, State flow is used to simulate the TPPN model, and the simulation of a case demonstrates that the approach is feasible and effective.

Petri Net Modeling and Analysis of Automated Container Terminal Using Automated Guided Vehicle Systems

Booming world trade, scarcity of land for yard expansion in many ports, and deployment of new, massive megaships have magnified the need to find better ways of performing container terminal operations. Automated guided vehicle systems (AGVS) have been proposed as possible candidates for future automated container operation because of their ability to significantly improve the performance of container terminals. However, before the deployment of AGVS, computer model simulations to investigate the potential problems are necessary to successfully implement the system. Petri net is a well-known modeling tool that, with the advantages of its graphic nature and the availability of mathematical analysis techniques, is clearly suitable for the application of automated container terminal systems (ACTS) modeling. A timed-place petri net (TPPN) model of ACTS using automated guided vehicles (AGVs) is constructed. The TPPN model contains a transportation layout module, two unit submodels, an AGV unit submodel, and a crane unit submodel. The transportation layout module serves as a basic unit to construct the transportation road map of the system. The AGV unit submodel is used to model the traveling behavior of the AGV on a node-to-node basis, and the crane unit submodel is used to model the crane’s container-loading and -unloading movement. A collision-free control rule, which is primely modeled using inhibitor and actuator arcs, is embedded in the submodels to ensure a collision-free environment for the AGVs. The important properties of the model such as liveness, safeness, and reversibility are analyzed.

A Petri net based approach to modeling and scheduling for an FMS and a case study

In this paper, a timed-place Petri net (TPPN) model for flexible manufacturing systems (FMSs) is constructed, which contains two major submodels: the stationary transportation model; and the variable process flow model. For multiple automated guided vehicle (AGV) systems, the authors embed a simple rule and introduce a push-AGV strategy in a TPPN model to solve the collision and traffic jam problems of such vehicles. Since a firing sequence of the TPPN from the initial marking to the final marking can be seen as a schedule of the modeled FMS, by using an A/sup */ based search algorithm, namely, the limited-expansion A algorithm, an effective schedule of the part processing can be obtained. To show the promising potential of the proposed work, a prototype FMS is used as a target system for implementation. The experiment results assert that the job-shop scheduling problem can always be satisfactorily solved.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>