Leon F. McGinnis

System and simulation modeling using SysML

Simulation languages and the GUIs supporting them may be excellent tools for creating simulation codes, but are not necessarily the best tools to use for creating descriptions of systems, i.e., for modeling. In 2006, OMG published the initial standard specification (OMG 2006) for SysML (Systems Modeling Language), an extension of UML (OMG 2007) designed specifically to support systems engineering. SysML shows great promise for creating object-oriented models of systems that incorporate not only software, but also people, material, and other physical resources, expressing both structure and behavior for such systems. In this paper, we explore the use of SysML both to model a system to be simulated and to support the automatic generation of simulation models.

A simple example of SysML-driven simulation

The successful practice of simulation requires a number of capabilities; two key capabilities are creating a conceptual model of the system to be simulated, and translating the conceptual model to a computational process or simulation program. We describe how OMGs new graphical systems modeling language, OMG SysML™ (OMG 2009), can be used to create a conceptual model, and how this conceptual model can be translated automatically to a simulation program. In demonstrating the process, we use Arena™ as the target simulation language, but the concepts presented are quite general.

A survey of challenges in modelling and decision-making for discrete event logistics systems

In this paper, we consider discrete event logistics systems (DELS). DELS are networks of resources through which material flow. They have been the subject of a large body of analytic research. A huge variety of specific models exists that generally require application by model and/or solution experts to answer narrowly-defined logistics questions about inventory, sourcing, scheduling, routing, etc. It has, however, proven difficult to integrate these models in any comprehensive way into information systems for logistics because of the lack of conceptual alignment between the models produced by researchers and the information systems deployed in practice with which they should be integrated. In this paper, we systematically identify several challenges for DELS research. We analyse the root of the difficulties for applying academic research results in DELS, and indicate some potential future research directions.

System modeling in sysml and system analysis in arena

A Model Driven Architecture approach is employed to support the practice of discrete-event simulation. OMGs System Model Language, OMG SysML™, is used to define a platform independent model (PIM) and auto-translate it into an appropriate platform specific model (PSM). The implementation and the nature of the transformation from PIM to PSM are clearly addressed to enable: (i) formal modeling of systems using their own semantics in SysML, (ii) SysML model verification and validation by stakeholders, (iii) automatic translation of system models expressed in SysML into analysis models as the PSM, and (iv) maintainability of this approach to accommodate system changes and extensions very easily. The proposed approach can be used for any analysis tool and application domain. In this paper, we choose to model transaction-based examples elicited from the manufacturing domain in SysML and translate them into Arena™ models using the Atlas Transformation Language.

Visual Analytics for Early-Phase Complex Engineered System Design Support

This article reports on our ongoing experiences in developing visual analytics tools for real-world CESs. Our work focuses on the early design phase during which a large design space is explored, poor alternatives are pruned, and valuable alternatives are considered further. Visual analytics tools can provide interactive discovery, exploration, and understanding of real-world complex engineered systems (CES). The proposed tool, which focuses on the early design phase, can help users perform routine CES design analysis tasks and offer stakeholder-specific visual representations of complex design models.

Simulation model generation of discrete event logistics systems (dels) using software design patterns

To provide automated access from a formal system model to multiple analysis tools, such as discrete event simulation or optimization, we extend current model-based systems engineering (MBSE) methodologies by introducing a new model to model transformation method based on object-oriented creational patterns from software design. Implemented in MATLABs discrete event simulation tool, SimEvents, we demonstrate the methodology by generating two distinct use cases based on a distribution supply chain and manufacturing system.

Modeling-based Design of Strategic Supply Chain Networks for Aircraft Manufacturing

Abstract The aerospace supply chain network has evolved and become more complex over the years. New methods are needed to design and analyze the system, and to establish the interactions between aircraft (product) design and supply chain (process) design. This paper aims to introduce a strategic multi-product, multi-period design model for the manufacturing of an aircraft wing-box with a planning horizon of the full program duration. The supply chain systems consist of a number of external suppliers, candidate manufacturing sites, and a number of customers at fixed locations. The design model is a mixed-integer linear programming optimization routine that minimizes the total time-discounted network cost. The model generates a system configuration that specifies the location and capacity of the manufacturing sites, the material flow, and the transportation routes within the network. The model is implemented using open-source tools, and has a comprehensive and flexible data structure to support the decision-making process during the early aircraft design stages.

Logistics systems modeling and simulation

Modern logistics systems are much more than simply networks of material flow. They involve collaboration between firms that are also competitors. The supply chain can be a key consideration in product design, with its design and operations influenced by concerns about uncertain energy costs, sustainability, economic security, and other complex issues. Because of these and other considerations, the contemporary practice in which an analysis model is the first “formal” model of the logistics system is no longer feasible. Rather, what is required for a sustainable practice of simulation in logistics is a model-based approach which begins with a formal language for capturing a defining description of the logistics system itself. This formal language must be sufficiently accessible to the logistics systems stakeholders so that they can validate the resulting system description. The resulting descriptive model will be the basis for subsequent analyses, including simulation. In this context, we address the requirements for such a formal language, describe our initial progress in developing such a language for logistics systems, and place it in the context of prior work on “reference models.”

On fidelity and model selection for discrete event simulation

In simulation, perhaps the most common use of the term ‘fidelity’ refers to the faithfulness with which model behavior reflects modeled system behavior. While there have been studies of fidelity seeking absolute and quantitative measures, there is not yet a consensus on a workable fidelity metric. We propose a formal modeling framework for comparing discrete event system simulation models in terms of fidelity, using a relative fidelity indicator. Based on the framework, we consider the possibility that the higher fidelity simulation models can also be more productive, even though they are more expensive to develop and use, since they can be used to achieve multiple objectives. First, we propose a formal simulation modeling framework within which the fidelity of simulation models can be discussed. With this framework and a simple example, we then define a relative fidelity indicator that provides a systematic way of comparing the fidelity of two simulation models. The relative fidelity indicator focuses on the most important characteristics in simulation studies: the input and output interfaces and the variables used for specifying a real-world system and simulation models. It does not require any special modeling formalism for model comparison. Based on the relative fidelity indicator and simulation modeling framework, we state the optimum simulation model selection problem to achieve given simulation objectives. Under a practical assumption, we analyze the simulation model selection problem and derive properties related to simulation modeling and the fidelity of simulation models.

A simulation optimization framework for discrete event logistics systems (DELS)

For large-scale, complex systems, both simulation and optimization methods are needed to support system design and operational decision making. Integrating the two methodologies, however, presents a number of conceptual and technical problems. This paper argues that the required integration can be successfully achieved, within a specific domain, by using a formal domain specific language for specifying instance problems and for structuring the analysis models and their interfaces. The domain must include a large enough class of problems to justify the resulting specialization of analysis models.