Discrete Event Simulation Applied to Aircraft Development

  The trend in aerospace industry is to increase product complexity, reduce costs and integrate processes along the aircraft lifecycle. Discrete event simulation provides an important support to this challenge. Discrete event simulation techniques are a flexible tool for the evaluation of solutions, comparison of productive scenarios, analysis the impact of modifications and introduction of new processes. However, the selection of the modeling method and simulation tool is not trivial. It impacts not only on the results but also on the effort required to run the simulation. In this context, this paper analyses the applicability of two modeling and simulation approaches in different phases of the aeronautical product lifecycle. It considers the use of event oriented simulation based on Petri nets and process oriented simulation, based on the commercial tool QUEST

Modular development of manufacturing simulation models.

It is common practice within manufacturing companies to create simulation models at different time periods. These models are often used to represent various parts of the manufacturing systems. In general, these pre-built simulation models are required to be integrated together in order to evaluate the entire manufacturing system, this is not a simple task. This research addresses the issues involved in the integration of pre-built simulation models. An in depth literature review was carried out to identify current strategies to overcome these issues. Based on structured research work, a set of recommendations is proposed to ensure easy integration of models. This set of recommendations will help simulation practitioners to minimise the errors occurred during the integration of simulation models. The findings conclude more effort is required than is anticipated by most model builders and involves far more than 'just simply changing' the name of variables. A set of recommendations is therefore proposed to cope with the complexity and understanding of manufacturing systems. The research focuses on manufacturing systems but in general can be applied elsewhere

Modular development of manufacturing simulation models.

It is common practice within manufacturing companies to create simulation models at different time periods. These models are often used to represent various parts of the manufacturing systems. In general, these pre-built simulation models are required to be integrated together in order to evaluate the entire manufacturing system, this is not a simple task. This research addresses the issues involved in the integration of pre-built simulation models. An in depth literature review was carried out to identify current strategies to overcome these issues. Based on structured research work, a set of recommendations is proposed to ensure easy integration of models. This set of recommendations will help simulation practitioners to minimise the errors occurred during the integration of simulation models. The findings conclude more effort is required than is anticipated by most model builders and involves far more than 'just simply changing' the name of variables. A set of recommendations is therefore proposed to cope with the complexity and understanding of manufacturing systems. The research focuses on manufacturing systems but in general can be applied elsewhere

Reusable modelling and simulation of flexible manufacturing for next generation semiconductor manufacturing facilities

Automated material handling systems (AMHS) in 300 mm semiconductor manufacturing facilities may need to evolve faster than expected considering the high performance demands on these facilities. Reusable simulation models are needed to cope with the demands of this dynamic environment and to deliver answers to the industry much faster. One vision for intrabay AMHS is to link a small group of intrabay AMHS systems, within a full manufacturing facility, together using what is called a Merge/Diverge link. This promises better operational performance of the AMHS when compared to operating two dedicated AMHS systems, one for interbay transport and the other for intrabay handling. A generic tool for modelling and simulation of an intrabay AMHS (GTIA-M&S) is built, which utilises a library of different blocks representing the different components of any intrabay material handling system. GTIA-M&S provides a means for rapid building and analysis of an intrabay AMHS under different operating conditions. The ease of use of the tool means that inexpert users have the ability to generate good models. Models developed by the tool can be executed with the merge/diverge capability enabled or disabled to provide comparable solutions to production demands and to compare these two different configurations of intrabay AMHS using a single simulation model. Finally, results from simulation experiments on a model developed using the tool were very informative in that they include useful decision making data, which can now be used to further enhance and update the design and operational characteristics of the intrabay AMHS

Modular development of manufacturing simulation models.

It is common practice within manufacturing companies to create simulation models at different time periods. These models are often used to represent various parts of the manufacturing systems. In general, these pre-built simulation models are required to be integrated together in order to evaluate the entire manufacturing system, this is not a simple task. This research addresses the issues involved in the integration of pre-built simulation models. An in depth literature review was carried out to identify current strategies to overcome these issues. Based on structured research work, a set of recommendations is proposed to ensure easy integration of models. This set of recommendations will help simulation practitioners to minimise the errors occurred during the integration of simulation models. The findings conclude more effort is required than is anticipated by most model builders and involves far more than 'just simply changing' the name of variables. A set of recommendations is therefore proposed to cope with the complexity and understanding of manufacturing systems. The research focuses on manufacturing systems but in general can be applied elsewhere

Methodology to develop hybrid simulation/emulation model.

Trends towards reduced life-time of products and globalised competition has increased pressure on manufacturing industries to be more responsive to changing needs of product markets. Consequently, the use of simulation to describe short term future performance of manufacturing system has become more significant than ever. An application of simulation that has attracted attention is for testing of control logic before commissioning on site by using a detailed simulation model called emulation model. However, though the success of using emulation particularly in improving cost-effectiveness of automated material handling system delivery has been acknowledged by industries and simulation model developers, the uptake for this technology is still low. The major inhibitors are the high costs of its model building as well as simulation and emulation models are perceived to be non convertible.The main objective, of this research is to establish a methodology to develop simulation model that can be converted into emulation model with ease, thus making emulation technology more affordable. The product of this research called the methodology to build Hybrid Simulation Emulation Model (HSEM) is a new approach of building emulation model comprising of three phases namely (1) development of base simulation model, (2) development of detail emulation model, and (3) integration of controller with the emulation model. Important requirements for HSEM are flexibility of adding details to the simulation model and inter process communication between model and real control system. To facilitate implementation of the methodology, it is essential that the simulation software package provide functionalities for modular model development, access and adding of codes, integration with other application and real time (RT) modelling.The methodology developed offers a more affordable emulation modelling and an opening for further research into the comprehensive support for the implementation of real time control system testing using emulation

Model representation and documentation in computer simulation.

Typically, simulation project is highly complex process, which relies heavily on the expertise and knowledge of the simulation analyst. It also requires the research of large amounts of systems data. This comprehensive data, together with the specialist skills of the analyst is integral to the success of any simulation project and it would seem obvious that a record of this information is ideally required for future references. However, it appears that, usually, very little or no effort is taken to record and maintain this significant information. This oversight often removes the opportunity for the subsequent use of the model by members of the project team themselves. It also hinders the reuse of simulation models in the development of future models that could use the same data. Hence, proper and complete documentation is seen as an essential requirement to overcome such situations. A simulation study involves, not only developing the model, but also managing the process prior to model construction and subsequent tasks. Documentation in simulation involves, not only recording the model description, but also other exhaustive details embraced with the whole project. Clearly, the project team and model re-users are benefited from such in-depth and effective documentation.Model Representation and Documentation (MRD) is a new concept for documentation in simulation. It addresses the different purposes or needs of different audiences in respect of the simulation project, model reuse, and other interested parties. No structured documentation methodology, either to satisfy this context, or to encompass the complete simulation project has been found in existing literature, or in simulation software. However, it is feasible that a progressive documentation with the model development process would fulfil the needs of different audiences and allows structuring the documentation process.The proposed MRD process is based on task-orientation, which is attributed to the system development methodology in software engineering. It offers the user the ability to manage the documentation process with micro-level of task documents and to capture project details as the project progresses. Subsequently, task documents are accumulated to produce complete documents to fulfil different purposes of documentation. Pre-structured forms of task documents, which are based on typical simulation project procedure and enriched with reusable model elements, not only provide the uniform and consistent structure to capture task details, but also offer a sound foundation for an integrated documentation system.An isolated MRD process, though concurrent with the model development, does not improve the present poor attempt to documentation. The integration of MRD process with model development offers the user the ability to perform both processes simultaneously as a single process while both are benefited directly and mutually through model exchange. The documentation models, which are constructed with reusable generic model elements, and the common database, which stores model details within a standard internal structure, make provision for such model exchange. Hence, an integrated MRD process improves, not only the documentation in simulation, but also model reusability.The study has produced a novel approach for documenting the details of simulation projects in an integrated environment.Samarakoon M. Piyasena