The paper analyses the dynamic performance of polyphase reluctance motors using damping and synchronising torques. A numerical algorithm has been applied to obtain these torque components in the time domain using deta...
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The paper analyses the dynamic performance of polyphase reluctance motors using damping and synchronising torques. A numerical algorithm has been applied to obtain these torque components in the time domain using detailed nonlinear models of reluctance motors. The effects of all electrical motor parameters have been examined and the optimum values of parameters, which give maximum damping of hunting oscillations, have been obtained. It has also been demonstrated that these optimum parameters substantially improve the dynamic performance of reluctance motors. The presented results form a guide to the production of reluctance motors with well-damped oscillations and improved dynamic performance.
This letter deals with the identification problem of a class of linear-in-parameters output error moving average systems. The difficulty of identification is that there exist some unknown variables in the information ...
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This letter deals with the identification problem of a class of linear-in-parameters output error moving average systems. The difficulty of identification is that there exist some unknown variables in the information vector. By means of the auxiliary model identification idea, an auxiliary model based recursive least squares algorithm is developed for identifying the parameters of the proposed system. The simulation results confirm the conclusion. (C) 2013 Elsevier Ltd. All rights reserved.
Many technological applications need of differential models either for their microscopic or macroscopic description and, frequently, they involve non-linear equations. There is a class of differential models that is t...
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Many technological applications need of differential models either for their microscopic or macroscopic description and, frequently, they involve non-linear equations. There is a class of differential models that is the diffusive-reaction type models that have a very large number of applications in different chemical engineering problems. These include transport and reaction in catalytic processes, heat and mass transfer in more than one phase, and electrostatic potentials in many current electrokinetic processes, just to name a few. Solutions to these models are either by linear approximations of the non-linear source, by other approximations of such non-linearity, or by numerical methods that frequently are heavily dependent of the mesh size for a successful convergence. In this contribution, an analytical-logarithmic approach is introduced and applied to unbounded domains of a rectangular, cylindrical, and spherical geometry for the case of electrostatic potential around a particle or an electrode in a given solution. Due to the lack of general methods to derive analytical solutions for differential models with non-linear sources, this study has focused on developing an efficient and economical procedure to obtain a formal analytical solution for such models that is used in a simple predictor-corrector approach to predict the correct solution. The proposed method involves the use of a recursive function,integral(AO), of the non-linear dependable variable that work as a corrector function. The procedure converts the non-linear ordinary differential equation in a simpler pseudo-linear ordinary differential equation whose analytical solution is later modified by means of the integral(AO) correction function to obtain the correct solution. The start of the algorithmic approach uses the case of integral(AO) = 1, that is the "true" solution to the linear approximation. Afterwards, the correction function is updated until convergence to the solution of the original non-
The adjoint method can determine design variables of an indoor environment according to the optimal design objective, such as minimal predicted mean vote (PMV) for thermal comfort. The method calculates the gradient o...
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The adjoint method can determine design variables of an indoor environment according to the optimal design objective, such as minimal predicted mean vote (PMV) for thermal comfort. The method calculates the gradient of the objective function over the design variables so that the objective function can be minimized along the fastest direction using an optimization algorithm. Since the objective function is controlled by the Reynolds-averaged Navier-Stokes (RANS) equations with the RNG k-epsilon model during the optimization process, all the corresponding adjoint equations should be solved, rather than the "frozen turbulence" assumption used in previous studies. This investigation developed adjoint equations for the RNG k-epsilon turbulence model and applied it to a two-dimensional ventilated cavity and a three-dimensional, two-person office. Design processes with the adjoint RNG k-epsilon turbulence model led to a near-zero design function for the two cases, while those with the "frozen turbulence" assumption did not. This investigation has successfully used the new method to design a two-person office with optimal thermal comfort level around the two occupants.
As a complex uncertain differential equation, how to solve the multi-dimensional uncertain differential equation is a complicated and difficult problem. This paper will be devoted to the a-path of some special multi-d...
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As a complex uncertain differential equation, how to solve the multi-dimensional uncertain differential equation is a complicated and difficult problem. This paper will be devoted to the a-path of some special multi-dimensional uncertain differential equations, namely, multi-factor uncertain differential equations, nested uncertain differential equations and multifactor nested uncertain differential equations. The alpha psi-path method is used to study the numerical solution problems of the above three special multi-dimensional uncertain differential equations. At the same time, the inverse uncertainty distributions and expected values of these three special multi-dimensional uncertain differential equations are also obtained. At last, the numerical algorithm examples are given to verify it.
The theory of conventional constrained molecular dynamics (MD) simulations is reexamined based on a projection operator approach. A new algorithm, named WIGGLE, is presented for MD simulations with internal constraint...
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The theory of conventional constrained molecular dynamics (MD) simulations is reexamined based on a projection operator approach. A new algorithm, named WIGGLE, is presented for MD simulations with internal constraints. At each time step, the algorithm utilizes the constrained accelerations derived from velocity adjustments to satisfy the hidden constraints, and provides both initial and final constrained values that are almost an order of magnitude closer to the desired values than does RATTLE. Its performance is compared with those of RATTLE and SHAKE for an octane molecule. Also presented are a formalism to additionally constrain the angular momentum about the center of mass and an expression for the local energy drift during each integration time step. (c) 2005 Elsevier Inc. All rights reserved.
The interval Newton method can be used for computing an enclosure of a single simple zero of a smooth function in an interval domain. It can practically be extended to allow computing enclosures of all zeros in a give...
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The interval Newton method can be used for computing an enclosure of a single simple zero of a smooth function in an interval domain. It can practically be extended to allow computing enclosures of all zeros in a given interval. This paper deals with the extended interval Newton method. An essential operation of the method is division by an interval that contains zero (extended interval division). This operation has been studied by many researchers in recent decades, but inconsistency in the research has occurred again and again. This paper adopts the definition of extended interval division redefined in recent documents (Kulisch in Arithmetic operations for floating-point intervals, 2009;Pryce in P1788: IEEE standard for interval arithmetic version 02.2, 2010). The result of the division is called the precise quotient set. Earlier definitions differ in the overestimation of the quotient set in particular cases, causing inefficiency in Newton's method and even leading to redundant enclosures of a zero. The paper reviews and compares some extended interval quotient sets defined during the last few decades. As a central theorem, we present the fundamental properties of the extended interval Newton method based on the precise quotient set. On this basis, we develop an algorithm and a convenient program package for the extended interval Newton method. Statements on its convergence are also given. We then demonstrate the performance of the algorithm through nine carefully selected very sensitive numerical examples and show that it can compute correct enclosures of all zeros of the functions with high efficiency, particularly in cases where earlier methods are less effective.
Semi-recursive formulations and their various versions have made it possible to describe complex nonlinear systems such as vehicles precisely while still solving the relevant equations of motion in real time. An optim...
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Semi-recursive formulations and their various versions have made it possible to describe complex nonlinear systems such as vehicles precisely while still solving the relevant equations of motion in real time. An optimal combination of an efficient multibody formulation and a fast numerical time integration scheme are needed to accurately simulate complex systems in real time. This paper introduces a double-step semi-recursive multibody formulation and analyzes its performance with high-order numerical time-integration algorithms for real-time simulation. The Runge-Kutta, Gill, Runge-Kutta-Fehlberg, Adams-Bashforth-Moulton, and adaptive time step Runge-Kutta numerical methods are explained and compared. Results are verified against a commercial multibody software solution. A 15-degree-of-freedom sedan vehicle model serves as a benchmark to verify the theoretical results. The results highlight the differences between the numerical algorithms and suggest appropriate approaches for a nonlinear vehicle dynamics model, particularly for cases where simulation times are long. (C) 2020 Elsevier Ltd. All rights reserved.
A new class of body-fitted grid system that can keep the third-order accuracy in time and space is proposed with the help of the CIP (constrained interpolation profile/cubic interpolated propagation) method. The grid ...
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A new class of body-fitted grid system that can keep the third-order accuracy in time and space is proposed with the help of the CIP (constrained interpolation profile/cubic interpolated propagation) method. The grid system consists of the straight lines and grid points moving along these lines like abacus - Soroban in Japanese. The length of each line and the number of grid points in each line can be different. The CIP scheme is suitable to this mesh system and the calculation of large CFL (>10) at locally refined mesh is easily performed. Mesh generation and searching of upstream departure point are very simple and almost mesh-free treatment is possible. Adaptive grid movement and local mesh refinement are demonstrated. (C) 2003 Elsevier B.V. All rights reserved.
We consider a type of optimal switching problems with non-uniform execution delays and ramping. Such problems frequently occur in the operation of economical and engineering systems. We first provide a solution to the...
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We consider a type of optimal switching problems with non-uniform execution delays and ramping. Such problems frequently occur in the operation of economical and engineering systems. We first provide a solution to the problem by applying a probabilistic method. The main contribution is, however, a scheme for approximating the optimal control by limiting the information in the state-feedback. In a numerical example the approximation routine gives a considerable computational performance enhancement when compared to a conventional algorithm.
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