SIMULATION: Transactions of The Society for Modeling and Simulation International

Mattila, Ville; Virtanen, Kai

doi: 10.1177/0037549714540008pmid: N/A

The maintenance scheduling problem of a fleet of fighter aircraft is considered through multi-objective simulation-optimization (MOSO). In the problem, a maintenance schedule consisting of target starting times of the maintenance activities of the aircraft is determined. The objectives are to minimize average deviation between the target and actual starting times of the activities and to maximize average aircraft availability. The objectives depend on the maintenance schedule through complex interactions due to a policy in which the need for maintenance is based on the flight hours of the aircraft cumulated during flight missions. In addition, the durations of the flight missions, maintenance activities, and failure repairs are uncertain. Therefore, an MOSO approach is applied to the problem. The approach includes a discrete-event simulation model and a state-of-the art multi-objective simulated annealing algorithm for determining non-dominated schedules. Moreover, a multi-attribute value (MAV) function is used for supporting a maintenance decision-maker (DM) in selecting the preferred non-dominated schedule for implementation. The MAV function captures incomplete information on the values of the objectives as well as on the DM’s preference statements regarding the weights of the objectives. The approach is implemented as an MOSO tool whereby the DM can consider the complex interactions and uncertainties of the problem which have not been addressed in the existing literature on maintenance scheduling. The approach and the tool are illustrated with a set of test problems as well as a real-life example problem.

Pasdar, Amir Hossein; Azadi, Shahram; Kazemi, Reza

doi: 10.1177/0037549714540027pmid: N/A

In a mechatronical approach, the design of a highly detailed, physically based model of a semi-automatic powertrain suitable for supervision has been explicated. In each part of the powertrain system, ultimately developed dynamical models have been exploited to make sure the whole model is up-to-date and is close to a real system. Advanced dynamical equations of an engine, a clutch, a gearbox and a driveline as well as a tire and a vehicle dynamic model for analyzing longitudinal performance have been considered. A well-suited automated manual transmission (AMT) along with a mean value transient spark-ignition (SI) engine model has been inserted to complete the solution. In order to simulate a real vehicle, the nonlinearities of the powertrain system mainly generated in the engine and clutch have drawn attention. Transient behavior of the system is a key parameter for design; hence, both steady-state and transient modeling such as of the gear shift procedure were considered. All parts of the model have been verified against experimental data. Finally, an overall simulation of the powertrain and vehicle in an in-city Economic Commission for Europe (ECE) cycle and a complete involved simulation of a gear shift process using Simulink have been performed to examine the level of the modeled dynamics. Lastly, it will be clear that use of nonlinear and real-world models can enhance the modeling and make it comparable to a real system.

Tang, Guolei; Wang, Wenyuan; Guo, Zijian; Yu, Xuhui; Wang, Bingchang

doi: 10.1177/0037549714540954pmid: N/A

An entrance channel is dredged when its natural dimensions are not adequate to accumulate more and larger ships. Considering the reconciliation among costs, safety and efficiency and the complex relationship among channel type, navigable water level and sailing speed, a simulation-based optimization framework is proposed to optimize channel dimensions with limited dredging budget constraints in an integrated way. In this framework, the optimization program generates channel dimensions acceptable for safe navigation with budget constraints, and seeks an optimal balance between the dredging costs and navigation efficiency, including vessel waiting time and berth utilization. The simulation model evaluates the values of navigation efficiency measures considering the randomness and dynamics in ship operation. Finally, an application is given and the results show that the proposed framework is effective and helpful for optimizing the dimensions of the entrance channel. Moreover, the proposed modeling and solution methods are general and can be applied to the port basin, anchorage area as well.

Ashtiani, Mehrdad; Abdollahi Azgomi, Mohammad

doi: 10.1177/0037549714540221pmid: N/A

The aim of this work is to propose a framework for the distributed simulation of cyber attacks based on high-level architecture (HLA), which is a commonly used standard for distributed simulations. The proposed framework and the corresponding simulator, which is called the distributed cyber attack simulator (abbreviated by DCAS), help administrators to model and evaluate the security measures of the networks. At the core of the DCAS is a simulation engine based on Portico, which is an open source HLA run-time infrastructure. The DCAS works in two modes: interactive and automated. Three types of simulation components (which are called federates in HLA terminology) are considered in the framework: the (1) network federate, (2) attacker federate and (3) defender federate. The simulator provides features for graphical design of the network models, animated traffic simulation, data collection, statistical analysis and different consoles for attacking and defending elements (e.g., intrusion detection systems, intrusion prevention systems). To increase the fidelity of the simulation outputs, real-world payloads are used by the DCAS. All the exploits information and the parameters of various network elements are automatically extracted from the open source vulnerability database. Also, the Snort rule-set is used as the signature database of the defending elements. The architecture and algorithms of the DCAS and the corresponding underlying simulation engine plus the security evaluation results of two illustrative examples are presented in this paper.

Agusdinata, Datu B; Lee, Seokcheon; Zhao, Fu; Thissen, Wil

doi: 10.1177/0037549714544081pmid: N/A

A full realization of alternative energy such as biofuels depends on the existence of a viable supply chain (SC) network. An agent-based simulation approach is pursued to understand the dynamics of the biofuels SC network. The interests of three SC actors are represented: users, biorefineries, and farmers. Each actor type has a binary decision option: adoption or non-adoption of biofuels. This SC network model is characterized by distributed control, time asynchrony, and resource contention among actors, who make decisions based on incomplete knowledge and delayed information. The decision dynamics of these actors are modeled using a computational ecosystem construct. A preliminary set of coupled payoff function for each actor type and each decision is developed to represent interdependencies among SC actors. The simulation model was used to evaluate three archetypes of subsidy policy. The SC network behavior is observed in terms of fraction of actors adopting the biofuel option. The SC network shows behaviors ranging from fixed point equilibrium under no delay and perfect knowledge to periodic and chaotic oscillations. The network behavior is very sensitive to the time delay parameter that partly influences the quality of information on which actors’ decisions are based. Several regions of SC behavior are identified. In particular, a chaotic behavior was observed. The work provides a methodological basis for further development, including identification of policies to control undesirable system behaviors.