Showing papers on "Modeling and simulation published in 2014"

On the modeling of carbon nanotubes: A critical review

Abstract: A comprehensive review is conducted on the modeling and simulation of isolated carbon nanotubes (CNTs) concentrating on all mechanical, buckling, vibrational and thermal properties Three different approaches consisting of atomistic modeling, continuum modeling and nano-scale continuum modeling are firstly explained and their applications toward understanding behavior of CNTs are discussed Different investigations available in literature focusing on mentioned behaviors are reviewed and their results are compared to show the applicability and efficiency of employed/developed technique Taking into account both runtime and accuracy of modeling, advantages and disadvantages of introduced methods are nominated and analyzed

Multiphysics NVH Modeling: Simulation of a Switched Reluctance Motor for an Electric Vehicle

Abstract: This paper presents a multiphysics modeling of a switched reluctance motor (SRM) to simulate the acoustic radiation of the electrical machine. The proposed method uses a 2-D finite-element model of the motor to simulate its magnetic properties and a multiphysics mechatronic model of the motor and controls to simulate operating conditions. Magnetic forces on the stator are calculated using finite-element analysis and are used as the excitation on a forced response analysis that contains a finite-element model of the motor stator structure. Finally, sound power levels are calculated using the boundary element method. Simulation results of the model are shown and compared with experimental measurements for a four-phase 8/6 SRM.

A review of modeling and simulation of laser beam machining

Abstract: Laser beam machining (LBM) is a widely used thermal advance machining process capable of high accuracy machining of almost any material with complex geometries. CO 2 and Nd:YAG lasers are mostly used for industrial purposes. Drilling, cutting, grooving, turning and milling are the applications of LBM with different material removal mechanisms. Modeling and simulation of the LBM process is indispensable for optimization purposes. Modeling can be done by implementing analytical, numerical, experimental and artificial intelligence-based methods. This paper provides a review of the various methods used for modeling and simulation of the laser beam machining process as well as key researches done in this field so far.

Mixed Effects Models for the Population Approach: Models, Tasks, Methods and Tools

Abstract: Wide-Ranging Coverage of Parametric Modeling in Linear and Nonlinear Mixed Effects Models: Mixed Effects Models for the Population Approach: Models, Tasks, Methods and Tools presents a rigorous framework for describing, implementing, and using mixed effects models. With these models, readers can perform parameter estimation and modeling across a whole population of individuals at the same time. Easy-to-Use Techniques and Tools for Real-World Data Modeling: The book first shows how the framework allows model representation for different data types, including continuous, categorical, count, and time-to-event data. This leads to the use of generic methods, such as the stochastic approximation of the EM algorithm (SAEM), for modeling these diverse data types. The book also covers other essential methods, including Markov chain Monte Carlo (MCMC) and importance sampling techniques. The author uses publicly available software tools to illustrate modeling tasks. Methods are implemented in Monolix, and models are visually explored using Mlxplore and simulated using Simulx. Careful Balance of Mathematical Representation and Practical Implementation: This book takes readers through the whole modeling process, from defining/creating a parametric model to performing tasks on the model using various mathematical methods. Statisticians and mathematicians will appreciate the rigorous representation of the models and theoretical properties of the methods while modelers will welcome the practical capabilities of the tools. The book is also useful for training and teaching in any field where population modeling occurs.

Aerodynamic Simulation of Vertical-Axis Wind Turbines

Abstract: Full-scale, 3D, time-dependent aerodynamics modeling and simulation of a Darrieus-type vertical-axis wind turbine (VAWT) is presented. The simulations are performed using a moving-domain finite-element-based ALE-VMS technique augmented with a sliding-interface formulation to handle the rotor-stator interactions present. We simulate a single VAWT using a sequence of meshes with increased resolution to assess the computational requirements for this class of problems. The computational results are in good agreement with experimental data. We also perform a computation of two side-by-side counterrotating VAWTs to illustrate how the ALE-VMS technique may be used for the simulation of multiple turbines placed in arrays.

3-D Electromagnetic Modeling of Parasitics and Mutual Coupling in EMI Filters

Abstract: The electromagnetic compatibility (EMC) analysis of electromagnetic interference (EMI) filter circuits using 3-D numerical modeling by the partial element equivalent circuit (PEEC) method represents the central topic of this paper. The PEEC-based modeling method is introduced as a useful tool for the prediction of the high frequency performance of EMI input filters, which is affected by PCB component placement and self- and mutual-parasitic effects. Since the measuring of all these effects is rather difficult and time consuming, the modeling and simulation approach represents a valuable design aid before building the final hardware prototypes. The parasitic cancellation techniques proposed in the literature are modeled by the developed PEEC-boundary integral method (PEEC-BIM) and then verified by the transfer function and impedance measurements of the L-C and C-L-C filter circuits. Good agreement between the PEEC-BIM simulation and the measurements is achieved in a wide frequency range. The PEEC-BIM method is implemented in an EMC simulation tool GeckoEMC. The main task of the presented research is the exploration of building an EMC modeling environment for virtual prototyping of EMI input filters and power converter systems.

3D modeling and simulation of 2G HTS stacks and coils

Abstract: Use of 2G HTS coated conductors in several power applications has become popular in recent years. Their large current density under high magnetic fields makes them suitable candidates for high power capacity applications such as stacks of tapes, coils, magnets, cables and current leads. For this reason, modeling and simulation of their electromagnetic properties is very desirable in the design and optimization processes. For many applications, when symmetries allow it, simple models consisting of 1D or 2D representations are well suited for providing a satisfying description of the problem at hand. However, certain designs such as racetrack coils and finite-length or non-straight stacks, do pose a 3D problem that cannot be easily reduced to a 2D configuration. Full 3D models have been developed, but their use for simulating superconducting devices is a very challenging task involving a large-scale computational problem. In this work, we present a new method to simulate the electromagnetic transient behavior of 2G HTS stacks and coils. The method, originally used to model stacks of straight superconducting tapes or circular coils in 2D, is now extended to 3D. The main idea is to construct an anisotropic bulk-like equivalent for the stack or coil, such that the geometrical layout of the internal alternating structures of insulating, metallic, superconducting and substrate layers is reduced while keeping the overall electromagnetic behavior of the original device. Besides the aforementioned interest in modeling and simulating 2G HTS coated conductors, this work provides a further step towards efficient 3D modeling and simulation of superconducting devices for large-scale applications.

Vehicle Dynamics: Modeling and Simulation

Abstract: The authors examine in detail the fundamentals and mathematical descriptions of the dynamics of automobiles. In this context different levels of complexity will be presented, starting with basic single-track models up to complex three-dimensional multi-body models. A particular focus is on the process of establishing mathematical models on the basis of real cars and the validation of simulation results. The methods presented are explained in detail by means of selected application scenarios.

Modeling and Simulation-Based Systems Engineering Handbook

Abstract: NASA Centers. Aerospace Companies, and Modeling and Simulation Tool Providers Survey of Model Based Systems Engineering Methodologies (6), (7). – e.g. INCOSE (16) INCOSE Systems Engineering Handbook, v. 3.2.2, October. Modeling and Simulation-Based Systems Engineering Handbook. Citation Information. Modeling and Simulation-Based Systems Engineering Handbook. Commercial Modeling and Simulation Tool Providers INCOSE Systems Engineering Handbook (7) CubeSat Mission Design Based on Systems.

Verification of aero‐elastic offshore wind turbine design codes under IEA Wind Task XXIII

Abstract: This work presents the results of a benchmark study on aero-servo-hydro-elastic codes for offshore wind turbine dynamic simulation. The codes verified herein account for the coupled dynamic systems including the wind inflow, aerodynamics, elasticity and controls of the turbine, along with the incident waves, sea current, hydrodynamics and foundation dynamics of the support structure. A large set of time series simulation results such as turbine operational characteristics, external conditions, and load and displacement outputs was compared and interpreted. Load cases were defined and run with increasing complexity to trace back differences in simulation results to the underlying error sources. This led to a deeper understanding of the underlying physical systems. In four subsequent phases—dealing with a 5-MW turbine on a monopile with a fixed foundation, a monopile with a flexible foundation, a tripod and a floating spar buoy—the latest support structure developments in the offshore wind energy industry are covered, and an adaptation of the codes to those developments was initiated. The comparisons, in general, agreed quite well. Differences existed among the predictions were traced back to differences in the model fidelity, aerodynamic implementation, hydrodynamic load discretization and numerical difficulties within the codes. The comparisons resulted in a more thorough understanding of the modeling techniques and better knowledge of when various approximations are not valid. More importantly, the lessons learned from this exercise have been used to further develop and improve the codes of the participants and increase the confidence in the codes’ accuracy and the correctness of the results, hence improving the standard of offshore wind turbine modeling and simulation. One purpose of this paper is to summarize the lessons learned and present results that code developers can compare to. The set of benchmark load cases defined and simulated during the course of this project—the raw data for this paper—is available to the offshore wind turbine simulation community and is already being used for testing newly developed software tools. Despite that no measurements are included, the large number of participants and the—in general—very fine level of agreement indicate high trustworthy results within the physical assumptions of the codes and the simulation cases chosen. Other cases, such as large prebend flexible blades, large wind shear, large yaw error or transient maneuvers, may not show the same level of agreement. These cases were deliberately left out because the focus is on the specific offshore application. Further on, this benchmark study includes participating codes and organizations by name (contrary to several previous benchmark studies) that gives the reader a chance to find results from one particular code of interest.Copyright © 2013 John Wiley & Sons, Ltd.

Modeling and simulation techniques in extreme nonlinear optics of gaseous and condensed media

Abstract: Computer simulation techniques for extreme nonlinear optics are reviewed with emphasis on the high light-intensity regimes in which both bound and freed electronic states contribute to the medium response and thus affect the optical pulse dynamics. The first part concentrates on the optical pulse propagation modeling, and provides a classification of various approaches to optical-field evolution equations. Light–matter interaction models are reviewed in the second part, which concentrates on methods that can be integrated with time- and space-resolved simulations encompassing realistic experimental scenarios.

Co-Simulation Training Platform for Smart Grids

Abstract: Power systems training and education faces serious challenges due to the rising complexity of energy systems. This paper presents a simulation-based training platform for educating students and power systems professionals in complex Smart Grid applications. The system is split into parts like electrical grid or controls and specialized, domain-specific tools are then coupled to be able to simulate the overall behavior. Experiences with the developed education and training material and the corresponding modeling and simulation environment are discussed. The usage of advanced modeling and simulation approaches, especially when providing new functionality via coupling of simulation, is an accessible way to train and educate students efficiently in the complex and interdisciplinary area of power systems.

PID & LQR control for a quadrotor: Modeling and simulation

Abstract: This paper aims to present a comparison between various controllers to be used in dynamic model of a quadrotor platform. The controllers assumed in this work are conventional PID and a classic LQR controller. The PID controller is chosen for quadrotor model because of its versatility and facile implementation, while also providing a good response for the model dynamics attitudes. The LQR controller seemed to be a good comparative controller due to its great performance and robustness in the plant. In this study, it is accomplished that both the controllers provide satisfactory feedback for quadrotor stabilization.

A Kriging Model for Dynamics of Mechanical Systems With Revolute Joint Clearances

Abstract: Over the past two decades, extensive work has been conducted on the dynamic effect of joint clearances in multibody mechanical systems. In contrast, little work has been devoted to optimizing the performance of these systems. In this study, the analysis of revolute joint clearance is formulated in terms of a Hertzian-based contact force model. For illustration, the classical slider-crank mechanism with a revolute clearance joint at the piston pin is presented and a simulation model is developed using the analysis/design software MSC.ADAMS. The clearance is modeled as a pin-in-a-hole surface-to-surface dry contact, with an appropriate contact force model between the joint and bearing surfaces. Different simulations are performed to demonstrate the influence of the joint clearance size and the input crank speed on the dynamic behavior of the system with the joint clearance. In the modeling and simulation of the experimental setup and in the followed parametric study with a slightly revised system, both the Hertzian normal contact force model and a Coulomb-type friction force model were utilized. The kinetic coefficient of friction was chosen as constant throughout the study. An innovative design-of-experiment (DOE)-based method for optimizing the performance of a mechanical system with the revolute joint clearance for different ranges of design parameters is then proposed. Based on the simulation model results from sample points, which are selected by a Latin hypercube sampling (LHS) method, a polynomial function Kriging meta-model is established instead of the actual simulation model. The reason for the development and use of the meta-model is to bypass computationally intensive simulations of a computer model for different design parameter values in place of a more efficient and cost-effective mathematical model. Finally, numerical results obtained from two application examples with different design parameters, including the joint clearance size, crank speed, and contact stiffness, are presented for the further analysis of the dynamics of the revolute clearance joint in a mechanical system. This allows for predicting the influence of design parameter changes, in order to minimize contact forces, accelerations, and power requirements due to the existence of joint clearance.

Cross-Layer Modeling and Simulation of Circuit Reliability

Abstract: Integrated circuit design in the late CMOS era is challenged by the ever-increasing variability and reliability issues. The situation is further compounded by real-time uncertainties in workload and ambient conditions, which dynamically influence the degradation rate. To improve design predictability and guarantee system lifetime, accurate modeling, and simulation tools for reliability are essential to both digital and analog circuits. This paper presents cross-layer solutions for emerging reliability threats, including: 1) device-level modeling of reliability mechanisms, such as transistor aging and its statistical behavior; 2) circuit-level long-term aging models that capture unique operation patterns in digital and analog design, and directly predict the degradation; and 3) simulation methods for very-large-scale designs. Built on the long-term model, the new methods significantly enhance the accuracy and efficiency of reliability analysis. As validated by silicon data, these solutions close the gap between the underlying reliability physics and circuit/system design for resilience.

Modeling and Simulation of Mechanical Micro-Machining—A Review

Abstract: This article provides a comprehensive review of literature on modeling and simulation that enhances the understanding of the process physics of the rapidly growing field of mechanical micro-machining. The article focuses on a number of micro-scale machining issues such as size effect, minimum chip thickness effect, micro-structure effects, and cutting tool dynamics which influence the underlying cutting mechanisms and the generated surface finish. We review the recent advances in modeling and simulation techniques, which include molecular dynamics simulation, finite element method, the newly emerging field of multi-scale simulation and mechanistic modeling. Some comments to emphasize the future requirements and directions of the modeling and simulation efforts in this field are also offered.

Dynamics and Control of Switched Electronic Systems: Advanced Perspectives for Modeling, Simulation and Control of Power Converters

Abstract: The increased efficiency and quality constraints imposed on electrical energy systems have inspired a renewed research interest in the study of formal approaches to the analysis and control of power electronics converters. Switched systems represent a useful framework for modeling these converters and the peculiarities of their operating conditions and control goals justify the specific classification of switched electronic systems. Indeed, idealized switched models of power converters introduce problems not commonly encountered when analyzing generic switched models or non-switched electrical networks. In that sense the analysis of switched electronic systems represents a source for new ideas and benchmarks for switched and hybrid systems generally. Dynamics and Control of Switched Electronic Systems draws on the expertise of an international group of expert contributors to give an overview of recent advances in the modeling, simulation and control of switched electronic systems. The reader is provided with a well-organized source of references and a mathematically-based report of the state of the art in analysis and design techniques for switched power converters. Intuitive language, realistic illustrative examples and numerical simulations help the reader to come to grips with the rigorous presentation of many promising directions of research such as: converter topologies and modulation techniques; continuous-time, discrete-time and hybrid models; modern control strategies for power converters; and challenges in numerical simulation. The guidance and information imparted in this text will be appreciated by engineers, and applied mathematicians working on system and circuit theory, control systems development, and electronic and energy conversion systems design.

Modeling and simulation of turbulent polydisperse gas-liquid systems via the generalized population balance equation

Abstract: This article reviews the most critical issues in the simulation of turbulent polydisperse gas-liquid systems. The discussion is here limited to bubbly flows, where the gas appears in the form of separate individual bubbles. First the governing equations are presented with particular focus on the Generalized Population Balance Equation (GPBE). Then the mesoscale models defining the evolution of the gas-liquid system (e.g. interface forces, mass transfer, coalescence and breakup) are introduced and critically discussed. Particular attention is devoted to the choice of the drag model to properly simulate dense gas-liquid systems in the presence of microscale turbulence. Finally the different solution methods, namely Lagrangian and Eulerian, are presented and discussed. The link between mixture, two- and multi-fluid models and the GPBE is also analyzed. Eventually the different methodologies to account for polydispersity, with focus on Lagrangian or Direct Simulation Monte Carlo (DSMC) methods and Eulerian Quadrature-based Moment Methods (QBMM), are also presented. A number of practical examples are discussed and the review is concluded by presenting advantages and disadvantages of the different methods and the corresponding computational costs

Constructive Models of Discrete and Continuous Physical Phenomena

Abstract: This paper studies the semantics of models for discrete physical phenomena, such as rigid body collisions and switching in electronic circuits. This paper combines generalized functions (specifically the Dirac delta function), superdense time, modal models, and constructive semantics to get a rich, flexible, efficient, and rigorous approach to modeling such systems. It shows that many physical scenarios that have been problematic for modeling techniques manifest as nonconstructive models, and that constructive versions of some of the models properly reflect uncertainty in the behavior of the physical systems that plausibly arise from the principles of the underlying physics. This paper argues that these modeling difficulties are not reasonably solved by more detailed continuous models of the underlying physical phenomena. Such more detailed models simply shift the uncertainty to other aspects of the model. Since such detailed models come with a high computational cost, there is little justification in using them unless the goal of modeling is specifically to understand these more detailed physical processes. All models in this paper are implemented in the Ptolemy II modeling and simulation environment and made available online.

Exact Hybrid Particle/Population Simulation of Rule-Based Models of Biochemical Systems

Abstract: Detailed modeling and simulation of biochemical systems is complicated by the problem of combinatorial complexity, an explosion in the number of species and reactions due to myriad protein-protein interactions and post-translational modifications. Rule-based modeling overcomes this problem by representing molecules as structured objects and encoding their interactions as pattern-based rules. This greatly simplifies the process of model specification, avoiding the tedious and error prone task of manually enumerating all species and reactions that can potentially exist in a system. From a simulation perspective, rule-based models can be expanded algorithmically into fully-enumerated reaction networks and simulated using a variety of network-based simulation methods, such as ordinary differential equations or Gillespie's algorithm, provided that the network is not exceedingly large. Alternatively, rule-based models can be simulated directly using particle-based kinetic Monte Carlo methods. This “network-free” approach produces exact stochastic trajectories with a computational cost that is independent of network size. However, memory and run time costs increase with the number of particles, limiting the size of system that can be feasibly simulated. Here, we present a hybrid particle/population simulation method that combines the best attributes of both the network-based and network-free approaches. The method takes as input a rule-based model and a user-specified subset of species to treat as population variables rather than as particles. The model is then transformed by a process of “partial network expansion” into a dynamically equivalent form that can be simulated using a population-adapted network-free simulator. The transformation method has been implemented within the open-source rule-based modeling platform BioNetGen, and resulting hybrid models can be simulated using the particle-based simulator NFsim. Performance tests show that significant memory savings can be achieved using the new approach and a monetary cost analysis provides a practical measure of its utility.

Modeling and Simulation Support for System of Systems Engineering Applications: Rainey/Modeling and Simulation Support for System of Systems Engineering Applications

Abstract: A little longer than a decade ago, the community of systems engineers started to seriously deal with a category of challenges: system of systems (SoS). Systems Engineering (SE) is now better understood since its official birth as a discipline in the middle of the last century. It is widely understood to control the total systems life cycle process: definition, development, deployment, and retirement of a system. SE ensures that solutions are reliable, maintainable, and cost-effective. But its solutions focus on a system made up of components born from a common set of user requirements. Interactions with other systems was always possible, but these other systems were external and beyond the central systems boundaries.

Modeling and Simulation of Complex Systems

Abstract: Two current major trends are that todays systems and processes are characterized by an increasing connectivity and that innovations and development take place in increasingly shorter cycles. The increasing connectivity of systems and processes leads to an increasing complexity due to the rapidly increasing number of possible states and interactions. The behavior of such complex systems is not determined by a single component, but results from the interactions of all system components. Typical examples include highly interconnected technical systems as well as social systems. The development, analysis and evaluation of such complex systems requires more and more the use of modeling and simulation, as it is often impossible to do otherwise. To represent such complex systems, microscopic modeling approaches like agent-based modeling and simulation are often used. Despite widespread use in many application areas, the foundations of agent-based modeling and simulation are much less profound than in other established modeling paradigms. This causes many difficulties: Efficient model development is hampered, verification and validation activities are difficult to perform and evaluation of reusability of model components is hardly possible. With special emphasis on agent-based modeling and simulation, this thesis aims at two goals. Firstly, improving effectivity and efficiency of model development and secondly, improving effectivity of model execution. The first contribution of this thesis is the definition of a General Reference Model for Agent-based Modeling and Simulation (GRAMS). This reference model defines the components and structure of agentbased models as well as constraints for the simulation of such models.

Circuit Design for Reliability

Abstract: This book presents physical understanding, modeling and simulation, on-chip characterization, layout solutions, and design techniques that are effective to enhance the reliability of various circuit units. The authors provide readers with techniques for state of the art and future technologies, ranging from technology modeling, fault detection and analysis, circuit hardening, and reliability management.