In this paper, an optimal PID-like controller is proposed for a spacecraft attitude stabilization problem subject to continuous inequality constraints on the spacecraft angular velocity and control, as well as termina...
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In this paper, an optimal PID-like controller is proposed for a spacecraft attitude stabilization problem subject to continuous inequality constraints on the spacecraft angular velocity and control, as well as terminal constraints on the spacecraft attitude and angular velocity. The closed-loop stability is established using the Lyapunov stability theory. The constraint transcription method and a local smoothing technique are used to construct a smooth approximate function for each of the continuous inequality constraints on the angular velocity and control. Then, by using the concept of the penalty function, these approximate smooth functions are appended to the quadratic performance criterion forming an augmented cost function. Consequently, the constrained optimal control problem under the PID-like controller is approximated by a sequence of optimal parameter selection problems subject to only terminal constraints on the spacecraft attitudes. A reliable computational algorithm is derived for the tuning of the optimal PID-like control parameters. Finally, numerical simulations are carried out to illustrate the effectiveness of the methodology proposed. (C) 2011 Elsevier Ltd. All rights reserved.
The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One habitual simplification is based on the assumption that lateral flow and transport i...
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The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One habitual simplification is based on the assumption that lateral flow and transport in unsaturated zone are not significant unless the capillary fringe is involved. In such cases the flow and transport in the unsaturated zone above groundwater level can be simulated as a 1D phenomenon, whereas the flow and transport through groundwater are viewed as 2D or 3D phenomena. A new approach for a numerical scheme for 3D variably saturated flow using quasi 3D Richards' equation and finite difference scheme is presented. The corresponding numerical algorithm and the QUASI-3D computer code were developed. Results of the groundwater level simulations were compared with transient laboratory experimental data for 2D data constant-flux infiltration, quasi-3D HYDRUS-MODFLOW numerical model and a FULL-3D numerical model using Richards' equation. Hypothetical 3D examples of infiltration, pumping and groundwater mound dissipation for different spatial-time scales are presented. Water flow simulation for the Alto Piura aquifer (Peru) demonstrates the QUASI-3D model application at the regional scale. Computationally the QUASI-3D code was found to be more efficient by an order of 10-300%, while being accurate with respect to the benchmark fully 3D variable saturation code, when the capillary fringe was considered. Published by Elsevier B.V.
An optimal control problem is considered for a distributed-parameter Goursat-Darboux system with controlled boundary conditions. For the numerical solution of the problem, an algorithm based on separability and minima...
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An optimal control problem is considered for a distributed-parameter Goursat-Darboux system with controlled boundary conditions. For the numerical solution of the problem, an algorithm based on separability and minimax theorems is constructed, which reduces the problem to finding the maximum of a concave functional defined in the class of one-variable functions.
The quasi-gasdynamic equation system and the numerical algorithm for non-stationary viscous gasdynamic flow calculations are presented. The quasi-gasdynamic equation system generalizes the Navier-Stokes equations and ...
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The quasi-gasdynamic equation system and the numerical algorithm for non-stationary viscous gasdynamic flow calculations are presented. The quasi-gasdynamic equation system generalizes the Navier-Stokes equations and differs from it by the additional dissipative terms. The numerical examples are presented. Copyright (C) 2007 John Wiley & Sons, Ltd.
Fragmentation is a well-known method of the parallelization of numerical algorithms and programs. algorithm fragmentation allows creating fragmented parallel programs that can be executed on parallel computers of diff...
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Fragmentation is a well-known method of the parallelization of numerical algorithms and programs. algorithm fragmentation allows creating fragmented parallel programs that can be executed on parallel computers of different types (multiprocessors and/or multicomputers) and can be dynamically tuned to all the available resources. Fragmentation of the often used numerical algorithms, their representation for inclusion into the library of parallel numerical subroutines and properties of the runtime system are considered.
This paper presents a novel high-stability electrically-driven algorithm for the simulation of the electromechanical actuation of electrostatic MEMS devices. The stability of this algorithm improves on that of voltage...
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ISBN:
(纸本)9781420085051
This paper presents a novel high-stability electrically-driven algorithm for the simulation of the electromechanical actuation of electrostatic MEMS devices. The stability of this algorithm improves on that of voltage- and charge-drive algorithms. Key in our algorithm are the use of a local charge density as driver for an adapted relaxation algorithm and the adequate selection of the bias node in the mesh. The high stability of this algorithm allows probing the electromechanical equilibrium locus way beyond the V-and Q-drive pull-in instabilities. The new algorithm allows investigating the effect of dielectric charging in deformable electrostatic MEMS devices and especially the narrowing of their equilibrium locus due to dielectric charging non-uniformities. We implement this algorithm in 2D for clamped-clamped beams of rectangular cross-section and take into account, among other things, distributed dielectric thickness, permittivity, rest air gap, actuation electrode and linearly distributed dielectric roughness.
The quasi-gasdynamic equation system and the numerical algorithm for non-stationary viscous gasdynamic flow calculations are presented. The quasi-gasdynamic equation system generalizes the Navier-Stokes equations and ...
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The quasi-gasdynamic equation system and the numerical algorithm for non-stationary viscous gasdynamic flow calculations are presented. The quasi-gasdynamic equation system generalizes the Navier-Stokes equations and differs from it by the additional dissipative terms. The numerical examples are presented. Copyright (C) 2007 John Wiley & Sons, Ltd.
Most football simulators available use computer simulation to mimic football motion in a virtual environment. These kinds of simulations, while fun and interactive, are primarily for entertainment rather than as a tra...
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ISBN:
(纸本)9781627482769
Most football simulators available use computer simulation to mimic football motion in a virtual environment. These kinds of simulations, while fun and interactive, are primarily for entertainment rather than as a training tool. In this paper, we present a virtual training system for football kicking based on computer sensing and football impact dynamics using real-time wireless feedback. It is designed as a computer-assisted training system that will give a kicker the ability to practice off the field and receive the detailed feedback comparable yet more quantitative than they would experience at a training camp. In addition, it enables football coaches with quantitative data to design player-specific training program for kickers in order to achieve a goal with more precision. The system includes a force-sensing panel to determine the position and velocity as initial data, real-time wireless feedback to calibrate the football kicking dynamics model, and an advanced visualization environment designed to recreate the realistic atmosphere of all major football stadiums. The system has been designed and tested in a lab environment. The preliminary results show that the wireless signal is sensitive enough to detect football positions on the fly. The data collected in real-time can be used to calibrate the football dynamics model in predicting the final position of the football with respect to the field goal, which is visualized using 3D stereoscopic technology.
Composite structure consists of a system of layers bonded together. The layers can have different mechanical properties and thicknesses. The main task is to predict the behavior of a laminate as a system of layers wit...
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ISBN:
(纸本)9780791854877
Composite structure consists of a system of layers bonded together. The layers can have different mechanical properties and thicknesses. The main task is to predict the behavior of a laminate as a system of layers with given properties. We suggest advanced kinematic scheme for structural calculation and heuristic numerical algorithm of prediction behavior of a multilayer structures with essentially diverse layer's stiffness. Kinematic scheme can be compared in adequacy with three-dimensional approach of structural calculation of thin multilayer laminate, but is more economical in view of required resource for numerical calculation.
In many scientific and practical tasks, the classical concepts for parameter identification are satisfactory and generally applied with success, although many specialized problems necessitate the use of methods create...
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ISBN:
(纸本)9783642346309
In many scientific and practical tasks, the classical concepts for parameter identification are satisfactory and generally applied with success, although many specialized problems necessitate the use of methods created with specifically defined assumptions and conditions. This paper investigates the method of parameter identification for the case where losses resulting from estimation errors can be described in polynomial form with additional asymmetry representing different results of under- and overestimation. Most importantly, the method presented here considers the conditionality of this parameter, which in practice means its significant dependence on other quantities whose values can be obtained metrologically. To solve a problem in this form the Bayes approach was used, allowing a minimum expected value of losses to be achieved. The methodology was based on the nonparametric technique of statistical kernel estimators, which freed the worked out procedure from forms of probability distributions characterizing both the parameter under investigation and conditioning quantities. As a result, a ready to direct use algorithm has been presented here.
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