Preisach-type Hysteresis Model Research Articles

The influence of hysteresis on the determination of the magnetocaloric effect in Gd5Si2Ge2

We present a non-equilibrium Preisach-type hysteresis model based on the first order magnetocaloric material Gd5Si2Ge2. The model is developed from isofield magnetization measurements and first order reversal curves, both of which constitute a new and detailed approach to characterizing and modelling magnetocaloric materials. It is shown that the model reproduces the magnetization data, directly measured adiabatic temperature changes and provides a good description of the material behavior under application conditions. We find that the material settles in an area of metastability under continuous magnetization cycles, which effectively limits the adiabatic temperature change by the amount of thermal hysteresis present. We suggest a straightforward method for realistic estimation of the magnetocaloric effect from indirect measurements.

Efficient modeling of vector hysteresis using a novel Hopfield neural network implementation of Stoner–Wohlfarth-like operators

Incorporation of hysteresis models in electromagnetic analysis approaches is indispensable to accurate field computation in complex magnetic media. Throughout those computations, vector nature and computational efficiency of such models become especially crucial when sophisticated geometries requiring massive sub-region discretization are involved. Recently, an efficient vector Preisach-type hysteresis model constructed from only two scalar models having orthogonally coupled elementary operators has been proposed. This paper presents a novel Hopfield neural network approach for the implementation of Stoner–Wohlfarth-like operators that could lead to a significant enhancement in the computational efficiency of the aforementioned model. Advantages of this approach stem from the non-rectangular nature of these operators that substantially minimizes the number of operators needed to achieve an accurate vector hysteresis model. Details of the proposed approach, its identification and experimental testing are presented in the paper.

Vector hysteresis modeling using octal clusters of coupled step functions

Recently, substantial efforts have been focused on the efficiency enhancement of vector Preisach-type model implementation methodologies. This paper presents a computationally efficient approach for implementing a vector Preisach-type hysteresis model through an ensemble of octal clusters of coupled step functions. Within this approach, each cluster can be tuned by proper selection of coupling factors to exhibit vector hysteresis properties, thus minimizing number of clusters needed to construct a vector Preisach-type model.

Efficient modeling of vector hysteresis using fuzzy inference systems

Abstract Vector hysteresis models have always been regarded as important tools to determine which multi-dimensional magnetic field–media interactions may be predicted. In the past, considerable efforts have been focused on mathematical modeling methodologies of vector hysteresis. This paper presents an efficient approach based upon fuzzy inference systems for modeling vector hysteresis. Computational efficiency of the proposed approach stems from the fact that the basic non-local memory Preisach-type hysteresis model is approximated by a local memory model. The proposed computational low-cost methodology can be easily integrated in field calculation packages involving massive multi-dimensional discretizations. Details of the modeling methodology and its experimental testing are presented.

Phenomenological hysteresis model for vapor-liquid phase transitions

In this paper a new, phenomenological, temperature dependent hysteresis model of the vapor-liquid first-order phase transitions is presented in order to improve the existing equation-of-state type diffuse interface methods implicated in homogeneous two phase flow models. The proposed hysteresis approach describes not only equilibrium but also non-equilibrium phase transitions. A saturation temperature dependent upper limit of the allowable supersaturation is proposed, this limit ensures that unstable conditions could be always avoided. To overcome the flowing system caused memory handling problems of classical Preisach-type hysteresis models, a partial differential equation based hysteresis operator is proposed to describe the statistics of a model fluid consists of bistable, constant-mass clusters of molecules.

First order reversal curves identification procedures for vector models of hysteresis

The first order reversal curves (FORCs) technique has been extensively used in the last years for the identification of parameters of Preisach-type models of hysteresis. The technique proved both accurate and robust for the identification of the Preisach distribution function but due to the relatively high computational complexity, it has only been applied to scalar models of hysteresis. The theoretical foundations of the procedure for the identification of parameters of vector Preisach models by using FORCs were established by Mayergoyz. However, to our knowledge, the numerical implementation of the technique has received very little attention in the literature and there is no experimental testing of this technique either. In this paper, we present for the first time results obtained for the identification of the vector Preisach distribution by using FORC diagrams for a magnetic tape with uniaxial anisotropy. We also tested the model with simulated data produced by a vectorial Preisach model in which the pseudoparticles’ equilibrium state was calculated with a Landau–Lifshitz–Gilbert algorithm.

Application of a Preisach-type hysteresis model to the magnetic evaluation of material degradation

Preisach-based magnetic characterization is applied as a non-destructive method to evaluate material degradation due to metal fatigue. At predetermined interruptions of the cyclic mechanical loading a set of first order symmetric and a set of second order minor magnetisation loops are measured and analysed using both the classical and the moving Preisach model. The evolution of microstructure dependent magnetic features such as the Preisach distribution function, the mean-field parameter k and the local coercive field distribution Q_{c}(h_{c}) is monitored: k increases and the peak value of Q_{c} decreases with the number of stress cycles. Moreover, for both parameters the rate of change is higher during the last 10% of the fatigue lifetime.

Efficient implementation of vector Preisach-type models using orthogonally coupled hysteresis operators

Vector hysteresis models are regarded as helpful tools that can be utilized in the simulation of multidimensional field-media interactions. Recently, substantial efforts have been focused on the refinement of vector Preisach-type models of hysteresis. The purpose of this paper is to present a computationally efficient vector Preisach-type hysteresis model constructed from only two scalar models having orthogonally inter-related elementary operators. Such a model is implemented via a linear neural network (LNN) fed from the outputs of discrete Hopfield neural network (DHNN) blocks having step activation functions. With this DHNN-LNN configuration, it is possible to carry out the identification process using well-established widely available algorithms. Details of the model, its identification, and experimental testing are presented.

Preisach-type hysteresis models in magnetic field computation

The paper illustrates the evolution of Preisach-type models of hysteresis, involving mean field effect, dynamic effect and vector behaviour and their capability to be included into finite element electromagnetic field computation. The study makes reference to 1D and 2D formulations developed under different simplifying assumptions. Particular attention is devoted to the use of fixed point technique which is found to be very advantageous for the solution of hysteretic problems. Some examples of the analysis of magnetic field problems with hysteresis are finally presented.

Characterization of nanostructured magnetic materials

One of the basic problems of characterizing magnetic nanocomposites is to get information about the statistical distribution of the defects, and shape, and size of the particles. It is desirable to use quick, reliable and inexpensive magnetic methods. Information is usually obtained from the measurements of the DC remanence loop and switching field distribution (SFD), and the application of Preisach type hysteresis models. The discrete Fourier transform of the DC remanence curve is directly related to the SFD, and its application is illustrated on the example of magnetic nanocomposites of Fe particles embedded into a ZnO matrix, prepared by reaction milling.

Simulation of field-temperature effects in magnetic media using anisotropic Preisach models

Prediction of temperature effects on magnetic properties has always been a topic of wide interest. In this paper, simulation of field-temperature effects in magnetic media is proposed by using a 2-D anisotropic Preisach-type hysteresis model. A technique for solving the identification problem of this model is developed. Experimental testing of the proposed model has been carried out on two different thin film hard disk samples. Comparison between measured and computed values indicate that the suggested model can lead to good qualitative, as well as quantitative, simulation results.

Hysteresis modeling and its application to soft magnetic materials

The main aspects of hysteresis in magnetic materials are reviewed, and some theoretical methods for their description are discussed. Particular emphasis is given to Preisach-type models of hysteresis, which yield a unified treatment of rate-independent phenomena, eddy-current dissipation and thermal relaxation. Expressions for the free energy and the entropy production are given, which provide a proper general basis for the interpretation of magnetization curves, losses, thermal relaxation. In particular, they permit one to clarify the nature of the states of minimum Gibbs energy and their relationship to the anhysteretic magnetization curve. Lines of possible development, concerning in particular the connection between microstructural and magnetic properties, are indicated.

Using neural networks in the identification of Preisach-type hysteresis models

The identification process of the classical Preisach-type hysteresis model reduces to the determination of the weight function of elementary hysteresis operators upon which the model is built. It is well known that the classical Preisach model can exactly represent hysteretic nonlinearities which exhibit wiping-out and congruency properties. In that case, the model identification can be analytically and systematically accomplished by using first-order reversal curves. If the congruency property is not exactly valid, the Preisach model can only be used as an approximation. It is possible to improve the model accuracy in this situation by incorporating more appropriate experimental data during the identification stage. However, performing this process using the traditional systematic techniques becomes almost impossible. In this paper, the machinery of neural networks is proposed as a tool to accomplish this identification task. The suggested identification approach has been numerically implemented and carried out for a magnetic tape sample that does not possess the congruency property. A comparison between measured data and model predictions suggests that the proposed identification approach yields more accurate results.

Field distribution and power loss assessment in conductive rod cores exhibiting hysteresis

Recently, a new numerical approach for core loss evaluation in media exhibiting hysteresis has been proposed for relatively long conductive rods, subject to surface excitation along their azimuthal direction. In this approach, the Crank-Nicolson finite-difference technique is used, while enact media properties are taken into account by utilizing Preisach-type models of hysteresis. The purpose of this paper is to provide some experimental verification of the aforementioned approach. Accuracy of this approach has been assessed for a 2 cm diameter, 25 cm long iron alloy rod. Voltage wave-forms and core losses corresponding to some controlled applied field frequencies and amplitudes were experimentally deduced. For every experimentally considered excitation amplitude and frequency, computations were performed rising the developed approach. Comparisons have demonstrated good quantitative agreements between the experimentally measured computed results. Sample comparison results are given in the paper.

Magnetostriction simulation using anisotropic vector Preisach-type models

Magnetic materials exhibiting gigantic magnetostriction, especially Terfenol, are currently being widely used in fine positioning and active vibration damping devices. By involving accurate magnetostriction models during design stages, precision of such devices may be significantly enhanced. In this paper a straight-forward approach that employs anisotropic vector Preisach-type hysteresis models in simulating field-stress effects on magnetic materials is presented. Formation of the proposed model is given and its identification problem is solved. The presented approach has been numerically implemented and numerous digital computer simulations have been performed for Terfenol material. Sample simulation results as well as comparisons with experimentally observed magnetostriction curves are reported in the paper.

Performance simulation of hysteresis motors using accurate rotor media models

Recently, there has been an increased demand for small and medium sized brushless-type synchronous motors. Among these types, hysteresis motors have been especially used in those applications requiring precise speed and constant starting torque capabilities. In the past, several digital techniques for simulating the performance of hysteresis motors have been developed. These technique, however, involved significant approximations to the rotor magnetic properties. The purpose of this paper is to present a numerical approach through which enact rotor magnetic properties can be incorporated in the developed simulation techniques by utilizing Preisach-type hysteresis models. Numerous simulations for a sample 3-phase motor have been performed. It is found that predicted v-i characteristics qualitatively matches similar published experimental results. Other results concerning the developed torque and harmonic content are also given in the paper.

Numerical implementation and testing of new vector isotropic Preisach-type models

Recently, new vector Preisach-type models of hysteresis, which mathematically incorporate both scalar and rotational experimental data in their identification process, have been introduced. In this paper, a detailed numerical implementation of these models is presented. Numerical testing is carried out by assessing the models capability to match some assumed data similar to those experimentally observed for isotropic magnetic media. Results and conclusions of this numerical testing are given in the paper. >

New Preisach-type models of hysteresis and their experimental testing

New Preisach-type models of scalar hysteresis are discussed and the results concerning experimental testing of these models are given.

Dynamic Preisach models of hysteresis

Novel Preisach-type models of hysteresis are introduced. Their distinctive feature is their ability to describe dynamic properties of hysteresis nonlinearities. The identification problem of fitting dynamic Preisach models to experimental data is discussed. Some recommendations concerning numerical implementation of these models are given. >