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Time Simulation (time + simulation)
Selected AbstractsA perturbation analysis of harmonic generation from saturated elements in power systemsELECTRICAL ENGINEERING IN JAPAN, Issue 4 2010Teruhisa Kumano Abstract Nonlinear phenomena such as saturation of magnetic flux have considerable effects in power systems analysis. It is reported that a failure in a real 500-kV system triggered islanding operation, where resultant even harmonics caused malfunctions in protective relays. It is also reported that the major origin of this wave distortion is nothing but unidirectional magnetization of the transformer iron core. Time simulation is widely used today to analyze phenomena of this type, but it has basically two shortcomings. One is that the time simulation takes too much computing time in the vicinity of inflection points in the saturation characteristic curve because certain iterative procedures such as N-R (Newton,Raphson) must be used and such methods tend to be caught in an ill-conditioned numerical hunting. The other is that such simulation methods sometimes do not aid an intuitive understanding of the studied phenomenon because all of the nonlinear equations are treated in matrix form and are not properly divided into understandable parts, as is done in linear systems. This paper proposes a new computation scheme that is based on the so-called perturbation method. Magnetic saturation of iron cores in a generator and a transformer are taken into account. The proposed method has a special feature to deal with the first shortcoming of the N-R-based time simulation method stated above. The proposed method does not use an iterative process to reduce the equation residue, but uses perturbation series, so that it is free of the ill-conditioning problem. The user need only calculate the perturbation terms one by one until the necessary accuracy is attained. In a numerical example treated in the present paper, first-order perturbation can achieve reasonably high accuracy, which means very fast computing time. In a numerical study, three nonlinear elements are considered. The calculation results are almost identical to the conventional N-R-based time simulation, which shows the validity of the method. The proposed method can be effectively used in screening where many case studies are needed. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 35,42, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20895 [source] Rider's net moment estimation using control force of motion system for bicycle simulatorJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 11 2004Jae-Cheol Shin One of the challenging problems with bicycle simulators is to deal with the virtual bicycle dynamics that is coupled with rider's motion. For the virtual bicycle dynamics calculation and the real time simulation, it is necessary to identify the control inputs from the rider as well as the virtual environments. The steering, pedaling, and braking torques can be easily measured by using torque sensors and the virtual environments can be generated and provided by a visual system. However, direct measurement of the rider's net moment that significantly affects the bicycle motion is not practical. In this work, it is shown that six control forces of the Stewart platform-based motion system can be used for effective estimation of the rider's net moment, incorporated with the sliding mode controller with perturbation estimation. © 2004 Wiley Periodicals, Inc. [source] Low-dimensional models for real time simulations of catalytic monolithsAICHE JOURNAL, Issue 7 2009Saurabh Y. Joshi Abstract We present accurate low-dimensional models for real time simulation, control, and optimization of monolithic catalytic converters used in automobile exhaust treatment. These are derived directly by averaging the governing equations and using the concepts of internal and external mass transfer coefficients. They are expressed in terms of three concentration and two temperature modes and include washcoat diffusional effects without using the concept of the effectiveness factor. The models reduce to the classical two-phase models in the limit of vanishingly thin washcoat. The models are validated by simulating the transient behavior of a three-way converter for various cases and comparing the predictions with detailed solutions. It is shown that these new models are robust and accurate with practically acceptable error, speed up the computations by orders of magnitude, and can be used with confidence for the real time simulation and control of monolithic and other catalytic reactors. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] A robust integrated controller/diagnosis aircraft applicationINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 12 2005Andrés Marcos Abstract In this paper, an application of the robust integrated control/diagnosis approach using ,, -optimization techniques to the nonlinear longitudinal dynamics of a Boeing 747-100/200 aircraft is presented. The integrated approach allows to address directly the trade-off between the conflicting controller and fault diagnosis objectives. The integrated design formulation (interconnection and weight selection) is defined using five LTI plants obtained through out the Up-and-Away flight envelope. Linear and nonlinear closed-loop time simulations are carried out under a realistic turbulence and noise environment. A comparison drawn with the non-integrated design of a controller and a diagnosis filter with the same objectives shows that the integrated case results in similar diagnosis characteristics but improved fault tolerant performance and ease of design. Copyright © 2005 John Wiley & Sons, Ltd. [source] Force field-dependant structural divergence revealed during long time simulations of Calbindin d9kJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2010Elad Project Abstract The structural and the dynamic features of the Calbindin (CaB) protein in its holo and apo states are compared using molecular dynamics simulations under nine different force fields (FFs) (G43a1, G53a6, Opls-AA, Amber94, Amber99, Amber99p, AmberGS, AmberGSs, and Amber99sb). The results show that most FFs reproduce reasonably well the majority of the experimentally derived features of the CaB protein. However, in several cases, there are significant differences in secondary structure properties, root mean square deviations (RMSDs), root mean square fluctuations (RMSFs), and S2 order parameters among the various FFs. What is more, in certain cases, these parameters differed from the experimentally derived values. Some of these deviations became noticeable only after 50 ns. A comparison with experimental data indicates that, for CaB, the Amber94 shows overall best agreement with the measured values, whereas several others seem to deviate from both crystal and nuclear magnetic resonance data. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Low-dimensional models for real time simulations of catalytic monolithsAICHE JOURNAL, Issue 7 2009Saurabh Y. Joshi Abstract We present accurate low-dimensional models for real time simulation, control, and optimization of monolithic catalytic converters used in automobile exhaust treatment. These are derived directly by averaging the governing equations and using the concepts of internal and external mass transfer coefficients. They are expressed in terms of three concentration and two temperature modes and include washcoat diffusional effects without using the concept of the effectiveness factor. The models reduce to the classical two-phase models in the limit of vanishingly thin washcoat. The models are validated by simulating the transient behavior of a three-way converter for various cases and comparing the predictions with detailed solutions. It is shown that these new models are robust and accurate with practically acceptable error, speed up the computations by orders of magnitude, and can be used with confidence for the real time simulation and control of monolithic and other catalytic reactors. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] | |||||||||||||