scholarly journals Coupling Strategies Investigation of Hybrid Atomistic-Continuum Method Based on State Variable Coupling

2017 ◽  
Vol 2017 ◽  
pp. 1-21 ◽  
Author(s):  
Qian Wang ◽  
Xiao-Guang Ren ◽  
Xin-Hai Xu ◽  
Chao Li ◽  
Hong-Yu Ji ◽  
...  
Keyword(s):  
Force Model ◽  
State Variables ◽  
State Variable ◽  
Continuum Region ◽  
Boundary Force ◽  
Atomistic Region ◽  
Minimum Disturbance ◽  
The Continuum ◽  
Coupling Strategies ◽  
Overlap Region

Different configurations of coupling strategies influence greatly the accuracy and convergence of the simulation results in the hybrid atomistic-continuum method. This study aims to quantitatively investigate this effect and offer the guidance on how to choose the proper configuration of coupling strategies in the hybrid atomistic-continuum method. We first propose a hybrid molecular dynamics- (MD-) continuum solver in LAMMPS and OpenFOAM that exchanges state variables between the atomistic region and the continuum region and evaluate different configurations of coupling strategies using the sudden start Couette flow, aiming to find the preferable configuration that delivers better accuracy and efficiency. The major findings are as follows:(1)theC→Aregion plays the most important role in the overlap region and the “4-layer-1” combination achieves the best precision with a fixed width of the overlap region;(2)the data exchanging operation only needs a few sampling points closer to the occasions of interactions and decreasing the coupling exchange operations can reduce the computational load with acceptable errors;(3)the nonperiodic boundary force model with a smoothing parameter of 0.1 and a finer parameter of 20 can not only achieve the minimum disturbance near the MD-continuum interface but also keep the simulation precision.

A Strain-Based Formulation for the Coupled Viscoelastic/Damage Behavior

2000 ◽  
Vol 68 (2) ◽  
pp. 304-311 ◽  
Author(s):  
K. Abdel-Tawab ◽  
Y. J. Weitsman
Keyword(s):  
Internal State ◽  
Internal State Variable ◽  
State Variables ◽  
Viscoelastic Creep ◽  
Damage Behavior ◽  
State Variable ◽  
Internal State Variables ◽  
Interfacial Cracks ◽  
Induced Changes ◽  
The Continuum

A strain-based thermodynamics framework is proposed for modeling the continuum damage behavior of viscoelastic materials. Damage is represented by an internal state variable in the form of a symmetric second rank tensor. The effect of damage on the constitutive behavior is introduced through direct coupling between the damage variable and the viscoelastic internal state variables. This approach accounts for time-dependent damage as well as damage-induced changes in material symmetry. Also, damage evolution is modeled by employing the concept of damage surfaces. This work is motivated by experimental observations of the response of swirl-mat and random chopped fiber mat polymeric composites where viscoelastic creep was accompanied by a multitude of fiber/matrix interfacial cracks.

scholarly journals Exploring the Limits of Floating-Point Resolution for Hardware-In-the-Loop Implemented with FPGAs

Electronics ◽  
2018 ◽  
Vol 7 (10) ◽  
pp. 219 ◽  
Author(s):  
Alberto Sanchez ◽  
Elías Todorovich ◽  
Angel de Castro
Keyword(s):  
The State ◽  
Floating Point ◽  
Hardware In The Loop ◽  
State Variables ◽  
Numerical Resolution ◽  
Digital Devices ◽  
State Variable ◽  
Simulation Step ◽  
Field Programmable ◽  
The Difference

As the performance of digital devices is improving, Hardware-In-the-Loop (HIL) techniques are being increasingly used. HIL systems are frequently implemented using FPGAs (Field Programmable Gate Array) as they allow faster calculations and therefore smaller simulation steps. As the simulation step is reduced, the incremental values for the state variables are reduced proportionally, increasing the difference between the current value of the state variable and its increments. This difference can lead to numerical resolution issues when both magnitudes cannot be stored simultaneously in the state variable. FPGA-based HIL systems generally use 32-bit floating-point due to hardware and timing restrictions but they may suffer from these resolution problems. This paper explores the limits of 32-bit floating-point arithmetics in the context of hardware-in-the-loop systems, and how a larger format can be used to avoid resolution problems. The consequences in terms of hardware resources and running frequency are also explored. Although the conclusions reached in this work can be applied to any digital device, they can be directly used in the field of FPGAs, where the designer can easily use custom floating-point arithmetics.

Analysis, Design, and Optimization of High Speed Vehicle Suspensions Using State Variable Techniques

1974 ◽  
Vol 96 (2) ◽  
pp. 193-203 ◽  
Author(s):  
J. K. Hedrick ◽  
G. F. Billington ◽  
D. A. Dreesbach
Keyword(s):  
High Speed ◽  
Optimization Problems ◽  
Vertical Plane ◽  
Computer Application ◽  
Vehicle Suspension ◽  
State Variables ◽  
State Variable ◽  
Suspension Parameters ◽  
Suspension Model ◽  
High Speed Vehicle

This article applies state variable techniques to high speed vehicle suspension design. When a reasonably complex suspension model is treated, the greater adaptability of state variable techniques to digital computer application makes it more attractive than the commonly used integral transform method. A vehicle suspension model is developed, state variable techniques are applied, numerical methods are presented, and, finally, an optimization algorithm is chosen to select suspension parameters. A fairly complete bibliography is included in each of these areas. The state variable technique is illustrated in the solution of two suspension optimization problems. First, the vertical plane suspension of a high speed vehicle subject to guideway and aerodynamic inputs will be analyzed. The vehicle model, including primary and secondary suspension systems, and subject to both heave and pitch motions, has thirteen state variables. Second, the horizontal plane suspension of a high speed vehicle subject to guideway and lateral aerodynamic inputs is analyzed. This model also has thirteen state variables. The suspension parameters of both these models are optimized. Numerical results are presented for a representative vehicle, showing time response, mean square values, optimized suspension parameters, system eigenvalues, and acceleration spectral densities.

scholarly journals State Variable Effects in Graphical Event Models

2020 ◽  
Author(s):  
Debarun Bhattacharjya ◽  
Dharmashankar Subramanian ◽  
Tian Gao
Keyword(s):  
Real World ◽  
Continuous Time ◽  
Point Processes ◽  
Temporal Dynamics ◽  
Search Algorithm ◽  
State Variables ◽  
Discrete State ◽  
State Variable ◽  
Event Models ◽  
Real World Datasets

Many real-world domains involve co-evolving relationships between events, such as meals and exercise, and time-varying random variables, such as a patient's blood glucose levels. In this paper, we propose a general framework for modeling joint temporal dynamics involving continuous time transitions of discrete state variables and irregular arrivals of events over the timeline. We show how conditional Markov processes (as represented by continuous time Bayesian networks) and multivariate point processes (as represented by graphical event models) are among various processes that are covered by the framework. We introduce and compare two simple and interpretable yet practical joint models within the framework with relevant baselines on simulated and real-world datasets, using a graph search algorithm for learning. The experiments highlight the importance of jointly modeling event arrivals and state variable transitions to better fit joint temporal datasets, and the framework opens up possibilities for models involving even more complex dynamics whenever suitable.

scholarly journals Climatological Features of the Weakly and Very Stably Stratified Nocturnal Boundary Layers. Part I: State Variables Containing Information about Regime Occupation

2019 ◽  
Vol 76 (11) ◽  
pp. 3455-3484 ◽  
Author(s):  
Carsten Abraham ◽  
Adam H. Monahan
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Static Stability ◽  
Wind Component ◽  
State Variables ◽  
Intermittent Turbulence ◽  
Additional Information ◽  
State Variable ◽  
Mean Wind Speed

Abstract The atmospheric nocturnal stable boundary layer (SBL) can be classified into two distinct regimes: the weakly SBL (wSBL) with sustained turbulence and the very SBL (vSBL) with weak and intermittent turbulence. A hidden Markov model (HMM) analysis of the three-dimensional state-variable space of Reynolds-averaged mean dry static stability, mean wind speed, and wind speed shear is used to classify the SBL into these two regimes at nine different tower sites, in order to study long-term regime occupation and transition statistics. Both Reynolds-averaged mean data and measures of turbulence intensity (eddy variances) are separated in a physically meaningful way. In particular, fluctuations of the vertical wind component are found to be much smaller in the vSBL than in the wSBL. HMM analyses of these data using more than two SBL regimes do not result in robust results across measurement locations. To identify which meteorological state variables carry the information about regime occupation, the HMM analyses are repeated using different state-variable subsets. Reynolds-averaged measures of turbulence intensity (such as turbulence kinetic energy) at any observed altitude hold almost the same information as the original set, without adding any additional information. In contrast, both stratification and shear depend on surface information to capture regime transitions accurately. Use of information only in the bottom 10 m of the atmosphere is sufficient for HMM analyses to capture important information about regime occupation and transition statistics. It follows that the commonly measured 10-m wind speed is potentially a good indicator of regime occupation.

Difference Synchronization of Identical and Nonidentical Chaotic and Hyperchaotic Systems of Different Orders Using Active Backstepping Design

2018 ◽  
Vol 13 (5) ◽  
Author(s):  
Eric Donald Dongmo ◽  
Kayode Stephen Ojo ◽  
Paul Woafo ◽  
Abdulahi Ndzi Njah
Keyword(s):  
Chaotic System ◽  
Initial Conditions ◽  
Lyapunov Stability Theory ◽  
The State ◽  
State Variables ◽  
State Variable ◽  
New Type ◽  
The Difference ◽  
Synchronization Scheme ◽  
Hyperchaotic Systems

This paper introduces a new type of synchronization scheme, referred to as difference synchronization scheme, wherein the difference between the state variables of two master [slave] systems synchronizes with the state variable of a single slave [master] system. Using the Lyapunov stability theory and the active backstepping technique, controllers are derived to achieve the difference synchronization of three identical hyperchaotic Liu systems evolving from different initial conditions, as well as the difference synchronization of three nonidentical systems of different orders, comprising the 3D Lorenz chaotic system, 3D Chen chaotic system, and the 4D hyperchaotic Liu system. Numerical simulations are presented to demonstrate the validity and feasibility of the theoretical analysis. The development of difference synchronization scheme has increases the number of existing chaos synchronization scheme.

scholarly journals Analysis of Resolution in Feedback Signals for Hardware-in-the-Loop Models of Power Converters

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1527
Author(s):  
María Sofía Martínez-García ◽  
Angel de Castro ◽  
Alberto Sanchez ◽  
Javier Garrido
Keyword(s):  
Power Converters ◽  
Design Criterion ◽  
Feedback Signal ◽  
Hardware In The Loop ◽  
State Variables ◽  
Gate Arrays ◽  
State Variable ◽  
Field Programmable ◽  
Programmable Gate Arrays ◽  
Optimum Width

One of the main techniques for debugging power converters is hardware-in-the-loop (HIL), which is used for real-time emulation. Field programmable gate arrays (FPGA) are the most common design platforms due to their acceleration capability. In this case, the widths of the signals have to be carefully chosen to optimize the area and speed. For this purpose, fixed-point arithmetic is one of the best options because although the design time is high, it allows the personalization of the number of bits in every signal. The representation of state variables in power converters has been previously studied, however other signals, such as feedback signals, can also have a big influence because they transmit the value of one state variable to the rest, and vice versa. This paper presents an analysis of the number of bits in the feedback signals of a boost converter, but the conclusions can be extended to other power converters. The purpose of this work is to study how many bits are necessary in order to avoid the loss of information, but also without wasting bits. Errors of the state variables are obtained with different sizes of feedback signals. These show that the errors in each state variable have similar patterns. When the number of bits increases, the error decreases down to a certain number of bits, where an almost constant error appears. However, when the bits decrease, the error increases linearly. Furthermore, the results show that there is a direct relation between the number of bits in feedback signals and the inputs of the converter in the global error. Finally, a design criterion is given to choose the optimum width for each feedback signal, without wasting bits.

Application of optimal control law to laser guided bomb

2018 ◽  
Vol 122 (1251) ◽  
pp. 785-797
Author(s):  
Takieddine Mouada ◽  
Milos V. Pavic ◽  
Bojan M. Pavkovic ◽  
Sasa Z. Zivkovic ◽  
Mirko S. Misljen
Keyword(s):  
Noise Removal ◽  
Control Law ◽  
State Variables ◽  
Linear Quadratic ◽  
State Variable ◽  
Guidance Law ◽  
Optimal Guidance ◽  
Differential Game Theory ◽  
Miss Distance ◽  
Guidance Laws

ABSTRACTThe paper presents a laser guided bomb guidance law based on the linear quadratic differential game theory, where a case of two perpendicular planes with two state variables in each plane has been considered. The Kalman filtering method has been used for noise removal from the measured signals and for estimation of the missing state variable values needed for the optimal guidance law. Optimisation has been conducted with respect to minimisation of the performance index. Comparative analysis of different guidance laws is done. A statistical analysis is performed to obtain the terminal miss distance in dependence on total flight time.

scholarly journals Hybrid State Variable Incremental Integral for Reconstructing Extreme Multistability in Memristive Jerk System with Cubic Nonlinearity

Complexity ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Mo Chen ◽  
Yang Feng ◽  
Han Bao ◽  
Bocheng Bao ◽  
Huagan Wu ◽  
...  
Keyword(s):  
Integral Transformation ◽  
Equilibrium Points ◽  
Mechanism Analysis ◽  
State Variables ◽  
Cubic Nonlinearity ◽  
Hybrid State ◽  
State Variable ◽  
Extreme Multistability ◽  
Memristive System ◽  
Jerk System

Memristive system with infinitely many equilibrium points has attracted much attention for the generation of extreme multistability, whose initial-dependent dynamics can be interpreted in a reduced-order model through incremental integral transformation of state variables. But, the memristive system with any extra nonlinear terms besides the memristor ones cannot be handled directly using this method. In addition, the transformed state variables could be divergent due to the asymmetry of the original system. To solve these problems, a hybrid state variable incremental integral (HSVII) method is proposed in this paper. With this method, the extreme multistability in a four-dimensional (4D) memristive jerk system with cubic nonlinearity is successfully reconstituted in a three-dimensional (3D) model and the divergent state variables are eliminated through ingenious linear state variable mapping. Thus, mechanism analysis and physical control of the special extreme multistability can readily be performed. A hardware circuit is finally designed and fabricated, and the theoretical and numerical results are verified by the experimental measurements. It is demonstrated that this HSVII method is effective for the analysis of multistable system with high-order nonlinearities.

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