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Space Formulation (space + formulation)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Extension of efficient predictive control to the nonlinear case

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 5 2005
M. Bacic
Abstract The combined use of the closed-loop paradigm, an augmented autonomous state space formulation, partial invariance, local affine difference inclusion, and polytopic invariance are deployed in this paper to propose an NMPC algorithm which, unlike earlier algorithms that have to tackle online a nonlinear non-convex optimization problem, requires the solution of a simple QP. The proposed algorithm is shown to outperform earlier algorithms in respect of size of region of attraction and online computational load. Conversely, for comparable computational loads, the proposed algorithm outperforms earlier algorithms in terms of optimality of dynamic performance. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Application of standard DFT theory for nonbonded interactions in soft matter: Prototype study of poly- para -phenylene

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2006
Marcelo Alves-Santos
Abstract We present a detailed analysis of the application of density functional theory (DFT) methods to the study of structural properties of molecular and supramolecular systems, using as a paradigmatic example three para -phenylene-based systems: isolated biphenyl, single chain poly- para -phenylene, and crystalline biphenyl. We use different functionals for the exchange correlation potential, the local density (LDA), and generalized gradient approximations (GGA), and also different basis sets expansions, localized, plane waves (PW), and mixed (localized plus PW), within the reciprocal space formulation for the hamiltonian. We find that regardless of the choice of basis functions, the GGA calculations yield larger interring distances and torsion angles than LDA. For the same XC approximation, the agreement between calculations with different basis functions lies within 1% (LDA) or 0.5% (GGA) for distances, and while PW and mixed basis calculations agree within 1° for torsion angles, the localized basis results show larger angles by , 8° and a nonmonotonic dependence on basis size, with differences within 6°. The most prominent features, namely the torsion between rings for isolated molecule and infinite chain, and planarity for the molecule in crystalline environment, are well reproduced by all DFT calculations. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 217,227, 2006 [source]

Formulation of dynamics, actuation, and inversion of a three-dimensional two-link rigid body system

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 10 2005
Hooshang Hemami
In this paper, three issues related to three-dimensional multilink rigid body systems are considered: dynamics, actuation, and inversion. Based on the Newton-Euler equations, a state space formulation of the dynamics is discussed that renders itself to inclusion of actuators, and allows systematic ways of stabilization and construction of inverse systems. The development here is relevant to robotic systems, biological modeling, humanoid studies, and collaborating man-machine systems. The recursive dynamic formulation involves a method for sequential measurement and estimation of joint forces and couples for an open chain system. The sequence can start from top downwards or from the ground upwards. Three-dimensional actuators that produce couples at the joints are included in the dynamics. Inverse methods that allow estimation of these couples from the kinematic trajectories and physical parameters of the system are developed. The formulation and derivations are carried out for a two-link system. Digital computer simulations of a two-rigid body system are presented to demonstrate the feasibility and effectiveness of the methods. © 2005 Wiley Periodicals, Inc. [source]

A new Bayesian formulation for Holt's exponential smoothing

JOURNAL OF FORECASTING, Issue 3 2009
Robert R. Andrawis
Abstract In this paper we propose a Bayesian forecasting approach for Holt's additive exponential smoothing method. Starting from the state space formulation, a formula for the forecast is derived and reduced to a two-dimensional integration that can be computed numerically in a straightforward way. In contrast to much of the work for exponential smoothing, this method produces the forecast density and, in addition, it considers the initial level and initial trend as part of the parameters to be evaluated. Another contribution of this paper is that we have derived a way to reduce the computation of the maximum likelihood parameter estimation procedure to that of evaluating a two-dimensional grid, rather than applying a five-variable optimization procedure. Simulation experiments confirm that both proposed methods give favorable performance compared to other approaches. Copyright © 2008 John Wiley & Sons, Ltd. [source]