Petri net approaches for modeling, controlling, and validating flexible manufacturing systems

In this dissertation, we introduce the fundamental ideas and constructs of Petri net models such as ordinary, timed, colored, stochastic, control, and neural, and present some studies that emphasize Petri nets theories and applications as extended research fields that provide suitable platforms in modeling, controlling, validating, and evaluating concurrent systems, information systems, and a versatile dynamic system and manufacturing systems;We then suggest some of extensions that help make Petri nets useful for modeling and analyzing discrete event systems and manufacturing systems models based on the context of a versatile manufacturing system, and applies extended Petri nets models to several manufacturing systems such as an assembly cell, an Automated Palletized Conveyor System, and a tooling machine to show increased modeling power and efficient analysis methods;Finally, Validation methods are presented for these models and results of a performance analysis from a deterministic and stochastic model are used to reorganize and re-evaluate a manufacturing system in order to increase its flexibility

Modeling and Analysis of Two-Part Type Manufacturing Systems

This paper presents a model and analysis of a synchronous tandem flow line that produces different part types on unreliable machines. The machines operate according to a static priority rule, operating on the highest priority part whenever possible, and operating on lower priority parts only when unable to produce those with higher priorities. We develop a new decomposition method to analyze the behavior of the manufacturing system by decomposing the long production line into small analytically tractable components. As a first step in modeling a production line with more than one part type, we restrict ourselves to the case where there are two part types. Detailed modeling and derivations are presented with a small two-part-type production line that consists of two processing machines and two demand machines. Then, a generalized longer flow line is analyzed. Furthermore, estimates for performance measures, such as average buffer levels and production rates, are presented and compared to extensive discrete event simulation. The quantitative behavior of the two-part type processing line under different demand scenarios is also provided.Singapore-MIT Alliance (SMA

Information-based Preprocessing of PLC Data for Automatic Behavior Modeling

Cyber-physical systems (CPS) offer immense optimization potential for manufacturing processes through the availability of multivariate time series data of actors and sensors. Based on automated analysis software, the deployment of adaptive and responsive measures is possible for time series data. Due to the complex and dynamic nature of modern manufacturing, analysis and modeling often cannot be entirely automated. Even machine- or deep learning approaches often depend on a priori expert knowledge and labelling. In this paper, an information-based data preprocessing approach is proposed. By applying statistical methods including variance and correlation analysis, an approximation of the sampling rate in event-based systems and the utilization of spectral analysis, knowledge about the underlying manufacturing processes can be gained prior to modeling. The paper presents, how statistical analysis enables the pruning of a dataset's least important features and how the sampling rate approximation approach sets the base for further data analysis and modeling. The data's underlying periodicity, originating from the cyclic nature of an automated manufacturing process, will be detected by utilizing the fast Fourier transform. This information-based preprocessing method will then be validated for process time series data of cyber-physical systems' programmable logic controllers (PLC)

QUICK-GEOMETRY, a rapid response method for mathematically modeling configuration geometry

The philosophy, development, and various applications of the QUICK-GEOMETRY system were outlined. This system provides a practical method for developing the geometry models that are essential to the operation of computer-based design and manufacturing systems. Of particular interest are the various methods for modeling surface geometry that are used by aerodynamic analysis codes

Applications of integrated design/analysis systems in aerospace structural design

Integrated structural analysis and design systems and structural optimization procedures are being used in a production environment. Successful use of these systems requires experienced personnel. Interactive computer graphics can and will play a significant role in the analysis, optimization, design and manufacturing areas. Practical structural optimization procedures are tools that must be made available to the team. Much work still needs to be done to tie finite-element modeling to actual design details which are being tracked on systems such as CADAM or CATIA. More work needs to be done to automate the detailed design and analysis process. More emphasis should be placed on the real design problems

Energy Demand Forecasting in an Automotive Manufacturing Plant

Energy analysis is an essential topic within a sustainable manufacturing strategy. To better understand the energy demand in a manufacturing plant, consideration of trends and patterns of energy consumption, and making predictions based on historical data is a promising approach. Time series analysis is a favorable method to be used; because of the rapid development in metering/sensor technology and computational systems, time series analysis can now be deployed on larger-scale systems. However, the application of time series models to manufacturing plant energy modeling is rare due to complexity. This paper augments traditional time series forecasting for manufacturing energy study, with the consideration of data trend and patterns, exogenous influential inputs, and potential overfitting issues. Automotive manufacturing plant electricity demand was used as a study case for the proposed modeling approach validation. In this research, time series analysis is shown to effectively capture the increasing trend and seasonal patterns in the energy demand of a vehicle manufacturing plant. Models with exogenous inputs show a better accuracy as measured by Mean Square Error, and are more robust to sudden deviations

Modeling and Analysis of Manufacturing Systems with Multiple-Loop Structures

Kanban and Constant Work-In-Process (CONWIP) control methods are designed to impose tight controls over inventory, while providing a satisfactory production rate. This paper generalizes systems with kanban or CONWIP control as assembly/disassembly networks with multiple-loop structures. We present a stochastic mathematical model which integrates the information control flows into material flows. Graph theory is used to analyze the multiple-loop structures. An efficient analytical algorithm is developed for evaluating the expected production rate and inventory levels. The performance of the algorithm is reported in terms of accuracy, reliability and speed.Singapore-MIT Alliance (SMA

Petri net modeling and analysis of an FMS cell

Petri nets have evolved into a powerful tool for the modeling, analysis and design of asynchronous, concurrent systems. This thesis presents the modeling and analysis of a flexible manufacturing system (FMS) cell using Petri nets. In order to improve the productivity of such systems, the building of mathematical models is a crucial step. In this thesis, the theory and application of Petri nets are presented with emphasis on their application to the modeling and analysis of practical automated manufacturing systems. The theory of Petri nets includes their basic notation and properties. In order to illustrate how a Petri net with desirable properties can be modeled, this thesis describes the detailed modeling process for an FMS cell. During the process, top-down refinement, system decomposition, and modular composition ideas are used to achieve the hierarchy and preservation of important system properties. These properties include liveness, boundedness, and reversibility. This thesis also presents two illustrations showing the method adopted to model any manufacturing systems using ordinary Petri nets. The first example deals with a typical resource sharing problem and the second the modeling of Fanuc Machining Center at New Jersey Institute of Technology. Furthermore, this thesis presents the analysis of a timed Petri net for cycle time, system throughput and equipment utilization. The timed (deterministic) Petri net is first converted into an equivalent timed marked graph. Then the standard procedure to find the cycle time for marked graphs is applied. Secondly, stochastic Petri net is analyzed using SPNP software package for obtaining the system throughput and equipment utilization. This thesis is of significance in the sense that it provides industrial engineers and academic researchers with a comprehensive real-life example of applying Petri net theory to modeling and analysis of FMS cells. This will help them develop their own applications

Modeling and Performance Analysis of Manufacturing Systems in Footwear Industry

This study deals with modeling and performance analysis of footwear manufacturing using arena simulation modeling software. It was investigated that modeling and simulation is a potential tool for modeling and analysis of manufacturing assembly lines like footwear manufacturing because it allows the researcher to experiment with different variables and controls the manufacturing process without affecting the real production system. In this study Arena simulation software is employed to model and measure performance of existing manufacturing systems of footwear. A footwear assembly plant producing a moccasin model shoe in Ethiopia with a total number of 19 major parts to be assembled on two consecutive assembly lines (stitching and lasting) were selected for the model. Furthermore, 39 and 37 activities were identified for stitching and lasting production line respectively. For each activity, 15 numbers of observations have taken using stopwatch. All the collected data are statistically analyzed using arena input analyzer for statistical significance and determination of expressions to be used in simulation modeling. A standard validated simulation model was developed and run for 41 replications. The result shows that the stitching assembly line is operating with a line balance efficiency of 58.7% and lasting assembly line 67.6%. In the course of action, about four major problems were identified and solved with five proposed scenarios of which the best scenario results in improvement of assembly line balance efficiency of 93.5 and 86.3% for stitching and lasting respectively. This Arena Simulation Model has considered the production resources like machineries, employees and processing time; activity precedence relationships; and production methods in developing and testing scenarios. It can be applied to other complex manufacturing industries wishing to analyze and improve the performance of the production systems.Keywords: Modeling Simulation Performance Analysis Footwear Manufacturin