João P. A. Bastos
Bio: João P. A. Bastos is an academic researcher from Universidade Federal de Santa Catarina. The author has contributed to research in topics: Finite element method & Electric motor. The author has an hindex of 21, co-authored 96 publications receiving 3529 citations.
Papers published on a yearly basis
••01 Jan 1997
TL;DR: This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems and discusses the main points in the application to electromagnetic design, including formulation and implementation.
Abstract: This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.
01 Apr 2003
TL;DR: The Galerkin method has been applied to 2D finite element computations in this paper for the purpose of solving 2D Eddy current problems in Cylindrical and Spherical Coordinates.
Abstract: PREFACE MATHEMATICAL PRELIMINARIES Introduction The Vector Notation Vector Derivation The Gradient The Divergence The Rotational Second-Order Operators Application of Operators to More than One Function Expressions in Cylindrical and Spherical Coordinates MAXWELL EQUATIONS, ELECTROSTATICS, MAGNETOSTATICS, AND MAGNETODYNAMIC FIELDS Introduction The EM Quantities Local Form of the Equations The Anisotropy The Approximation of Maxwell's Equations The Integral Form of Maxwell's Equations Electrostatic Fields Magnetostatic Fields Magnetodynamic Fields BRIEF PRESENTATION OF THE FINITE ELEMENT METHOD Introduction The Galerkin Method - Basic Concepts A First-Order Finite Element Program Generalization of the Finite Element Method Numerical Integration Some 2D Finite Elements Coupling Different Finite Elements Calculation of Some Terms in the Field Equation A Simplified 2D Second-Order Finite Element Program THE FINITE ELEMENT METHOD APPLIED TO 2D ELECTROMAGNETIC CASES Introduction Some Static Cases Application to 2D Eddy Current Problems Axi-Symmetric Application Advantages and Limitation of 2D Formulations Non-Linear Applications Geometric Repetition of Domains Thermal Problems Voltage-Fed Electromagnetic Devices Static Examples Dynamic Examples COUPLING OF FIELD AND ELECTRICAL CIRCUIT EQUATIONS Introduction Electromagnetic Equations Equations for Different Conductor Configurations Connections Between Electromagnetic Devices and External Feeding Circuits Examples MOVEMENT MODELING FOR ELECTRICAL MACHINES Introduction The Macro-Element The Moving Band The Skew Effect in Electrical Machines Using 2D Simulation Examples INTERACTION BETWEEN ELECTROMAGNETIC AND MECHANICAL FORCES Introduction Methods Based on Direct Formulations Methods Based on the Force Density Electrical Machine Vibrations Originated by Magnetic Forces Example of Coupling Between the Field and Circuit Equations, Including Mechanical Transients IRON LOSSES Introduction Eddy Current Losses Hysteresis Anomalous or Excess Losses Total Iron Losses The Jiles-Atherton Model The Inverse Jiles-Atherton Model Including Iron Losses in Finite Element Calculations BIBLIOGRAPHY INDEX
01 Jan 1992
TL;DR: In this article, an introduction to electromagnetics emphasizes the computation of electromagnetic fields and the development of theoretical relations and avoids the lengthy discussions of electro - and magneto - statics that are customary in texts on EMG.
Abstract: This introduction to electromagnetics emphasizes the computation of electromagnetic fields and the development of theoretical relations. Beginning with the idea that Maxwell's equations are primary, the authors avoid the lengthy discussions of electro - and magneto - statics that are customary in texts on electromagnetism. After a chapter, therefore, on the basics of vector calculus, the discussion begins with the electromagnetic field and Maxwell's equations; the two following chapters then present the special cases of electrostatic and magnetostatic phenomena. Dynamics is introduced in chapter 5, and electromagnetic induction in chapter 6. The discussion of wave propagation and high-frequency fields emphasizes such practical matters as propagation in lossy dielectrics, waveguides, and resonators. The remaining four chapters discuss computational techniques; the finite element method, Galerkin's residual approach, software implementation, and recent developments in computer techniques.
TL;DR: In this paper, a modified Jiles-Atherton model presented the magnetic induction as an independent variable is proposed in order to directly used in time-stepping finite-element calculations applied to the magnetic vector potential formulation.
Abstract: A modified Jiles-Atherton model presenting the magnetic induction as an independent variable is proposed in order to be directly used in time-stepping finite-element calculations applied to the magnetic vector potential formulation. This model is implemented in the field calculation procedure by introducing a differential reluctivity. The calculated results are validated by experiences performed in an Epstein's frame.
TL;DR: In this article, a modified Langevin equation is used to represent the anhysteretic vector magnetization, and a comparison between measured and calculated curves for an anisotropic soft magnetic material is performed to validate the model.
Abstract: In this paper, we present a new vector hysteresis model, which is derived from the original Jiles-Atherton scalar one. The model presents the magnetic vector induction as the independent variable. A modified Langevin equation is used to represent the anhysteretic vector magnetization, and some model aspects are discussed. A comparison between measured and calculated curves for an anisotropic soft magnetic material is performed to validate the model.
TL;DR: A wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives are reviewed.
Abstract: Permanent magnet AC (PMAC) motor drives are finding expanded use in high-performance applications where torque smoothness is essential. This paper reviews a wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives. Sinusoidal PMAC drives generally show the greatest potential for pulsating torque minimization using well-known motor design techniques such as skewing and fractional slot pitch windings. In contrast, trapezoidal PMAC drives pose more difficult trade-offs in both the motor and controller design which may require compromises in drive simplicity: and cost to improve torque smoothness. Controller-based techniques for minimizing pulsating torque typically involve the use of active cancellation algorithms which depend on either accurate tuning or adaptive control schemes for effectiveness. In the end, successful suppression of pulsating torque ultimately relies on an orchestrated systems approach to all aspects of the PMAC machine and controller design which often requires a carefully selected combination of minimization techniques.
TL;DR: An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented in this paper, which provides dimensionless expressions for the contact load, contact area and mean contact pressure, covering a large range of interference values from yielding inception to fully plastic regime of the spherical contact zone.
Abstract: An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. The model provides dimensionless expressions for the contact load, contact area, and mean contact pressure, covering a large range of interference values from yielding inception to fully plastic regime of the spherical contact zone. Comparison with previous elastic-plastic models that were based on some arbitrary assumptions is made showing large differences. ©2002 ASME
•01 May 1997
TL;DR: The cornerstone of this dissertation is a collection of theory relating Krylov projection to rational interpolation, based on which three algorithms for model reduction are proposed, which are suited for parallel or approximate computations.
Abstract: This dissertation focuses on efficiently forming reduced-order models for large, linear dynamic systems. Projections onto unions of Krylov subspaces lead to a class of reduced-order models known as rational interpolants. The cornerstone of this dissertation is a collection of theory relating Krylov projection to rational interpolation. Based on this theoretical framework, three algorithms for model reduction are proposed. The first algorithm, dual rational Arnoldi, is a numerically reliable approach involving orthogonal projection matrices. The second, rational Lanczos, is an efficient generalization of existing Lanczos-based methods. The third, rational power Krylov, avoids orthogonalization and is suited for parallel or approximate computations. The performance of the three algorithms is compared via a combination of theory and examples. Independent of the precise algorithm, a host of supporting tools are also develop ed to form a complete model-reduction package. Techniques for choosing the matching frequencies, estimating the modeling error, insuring the model's stability, treating multiple-input multiple-output systems, implementing parallelism, and avoiding a need for exact factors of large matrix pencils are all examined to various degrees
TL;DR: An introduction to IGA applied to simple analysis problems and the related computer implementation aspects is presented, and implementation of the extended IGA which incorporates enrichment functions through the partition of unity method (PUM) is presented.
Abstract: Isogeometric analysis (IGA) represents a recently developed technology in computational mechanics that offers the possibility of integrating methods for analysis and Computer Aided Design (CAD) into a single, unified process. The implications to practical engineering design scenarios are profound, since the time taken from design to analysis is greatly reduced, leading to dramatic gains in efficiency. In this manuscript, through a self-contained Matlab® implementation, we present an introduction to IGA applied to simple analysis problems and the related computer implementation aspects. Furthermore, implementation of the extended IGA which incorporates enrichment functions through the partition of unity method (PUM) is also presented, where several examples for both two-dimensional and three-dimensional fracture are illustrated. We also describe the use of IGA in the context of strong-form (collocation) formulations, which has been an area of research interest due to the potential for significant efficiency gains offered by these methods. The code which accompanies the present paper can be applied to one, two and three-dimensional problems for linear elasticity, linear elastic fracture mechanics, structural mechanics (beams/plates/shells including large displacements and rotations) and Poisson problems with or without enrichment. The Bezier extraction concept that allows the FE analysis to be performed efficiently on T-spline geometries is also incorporated. The article includes a summary of recent trends and developments within the field of IGA.
TL;DR: In this paper, a review is devoted to some inverse problems arising in the context of linear elasticity, namely the identification of distributions of elastic moduli, model parameters or buried objects such as cracks.
Abstract: This review is devoted to some inverse problems arising in the context of linear elasticity, namely the identification of distributions of elastic moduli, model parameters or buried objects such as cracks. These inverse problems are considered mainly for three-dimensional elastic media under equilibrium or dynamical conditions, and also for thin elastic plates. The main goal is to overview some recent results, in an effort to bridge the gap between studies of a mathematical nature and problems defined from engineering practice. Accordingly, emphasis is given to formulations and solution techniques which are well suited to general-purpose numerical methods for solving elasticity problems on complex configurations, in particular the finite element method and the boundary element method. An underlying thread of the discussion is the fact that useful tools for the formulation, analysis and solution of inverse problems arising in linear elasticity, namely the reciprocity gap and the error in constitutive equation, stem from variational and virtual work principles, i.e., fundamental principles governing the mechanics of deformable solid continua. In addition, the virtual work principle is shown to be instrumental for establishing computationally efficient formulae for parameter or geometrical sensitivity, based on the adjoint solution method. Sensitivity formulae are presented for various situations, especially in connection with contact mechanics, cavity and crack shape perturbations, thus enriching the already extensive known repertoire of such results. Finally, the concept of topological derivative and its implementation for the identification of cavities or inclusions are expounded.