Ciro Visone

Magnetic hysteresis modeling via feed-forward neural networks

A general neural approach to magnetic hysteresis modeling is proposed. The general memory storage properties of systems with rate independent hysteresis are outlined. Thus, it is shown how it is possible to build a neural hysteresis model based on feed-forward neural networks (NNs) which fulfills these properties. The identification of the model consists in training the NNs by usual training algorithms such as backpropagation. Finally, the proposed neural model has been tested by comparing its predictions with experimental data.

Models of magnetic hysteresis based on play and stop hysterons

This paper deals with mathematical models of magnetic hysteresis implemented by assembling hysterons of play and stop type. A procedure for the identification of these models is described, and their behaviors are compared to experimental results. A comparison to the Preisach and Prandtl-Ishlinskii models is performed. It is shown that the Play-Type Model is a possible alternative to Preisachs algorithm, whereas the Stop-Type Model is apt to represent the inverse of Preisachs operator. Simulations adopting both models are reported and compared to experimental data. Moreover, an application to the analysis of a ferroresonant circuit is studied, both numerically and experimentally.

Effects of hysteresis compensation in feedback control systems

Analyzes the performances of closed-loop control systems when real hysteretic actuators (e.g., Terfenol-D-based devices) are of concern. Shown is a simple but effective strategy, based on the simple idea of pseudo-compensator, for transducers hysteresis compensation. Such a strategy improves the control systems behavior, not only in terms of tracking error reduction but also in decreasing the control signal so as to avoid saturation and harmful stress to the actuator on the one hand and reducing hysteretic energy losses on the other. Experiments are performed on a magnetostrictive actuator used for a micropositioning task.

Experimental tests of a magnetostrictive energy harvesting device toward its modeling

This paper deals with a recently proposed device for energy harvesting from environmental vibrations, employing a magnetostrictive material. Even if most of the modeling efforts were focused on a linear approach, more complex and nontrivial phenomena are experimentally observed. A sample of such nontrivial behaviors, suggesting the definition of potentially more effective models, is described and discussed in this paper.

Capacitive Load Effects on a Magnetostrictive Fully Coupled Energy Harvesting Device

Vibration energy harvesting is a promising method to feed ultra-low power devices as wireless sensors, mems, etc. The accuracy of the design of the harvesting device, and then the harvested power, strongly depends on the modeling quality of the magnetostrictive relationships and on the device modeling in general. A further important issue is the optimization of the converted power with respect to the frequency of the vibration source, which is critical for low frequencies. The use of a capacitor in the electric circuit allows more harvested power at low frequencies and open the possibility of power optimizing stages. This analysis could be reliably carried out only in connection to a sufficiently realistic modeling of the employed material. Aim of the paper is therefore to study, by the definition of a simple nonlinear model, the effects of the capacitive load and of the mechanical source on the power conversion performances of the device. Several numerical examples are presented and discussed.

Feedback control systems for micropositioning tasks with hysteresis compensation

This paper proposes the analysis of a control loop system employing a Terfenol-D actuator driving a real mechanical load. The aim of the paper is to analyze the performances of such a system when a strategy of hysteresis compensation is employed. Such strategy has demonstrated its effectiveness in simpler feedback systems (with no mechanical load) by improving the tracking error, decreasing the control signal so as to avoid saturation and harmful stress to the actuator. As a consequence, the algorithm allows also to reduce energy losses in the actuator.

A Two-Port Nonlinear Model for Magnetoelastic Energy-Harvesting Devices

The aim of this paper is to present a two-port equivalent circuit that is able to describe the main features of an energy-harvesting device based on magnetoelastic materials. The magnetomechanical model behind the equivalent circuit is nonlinear and fully coupled. Therefore, the most part of the typical real-device behavior, without the limits of linear magnetomechanical modeling, is described. A preliminary validation of the model, by exploiting experimental data, is provided. Moreover, simulation tests and comparisons to the linear model are also carried out to underline the basic features of the proposed nonlinear approach. To this end, numerical results of the harvested power and peak voltage for the two devices in different working conditions are presented and discussed.

Fully coupled modeling of magneto-mechanical hysteresis through ‘thermodynamic’ compatibility

The paper proposes a phenomenological model for magneto-elastic interactions in materials with hysteresis, where both mechanical and magnetic variables are fully coupled. The approach allows one to provide a tool for the description of the energy conversion mechanism in the presence of losses, for example, in harvesting devices. The present approach takes into account exchange between mechanical and magnetic energies, as well as dissipation due to hysteresis phenomena. Using the concept of hysteresis potentials, it is shown that the model is consistent with classical nonequilibrium thermodynamics. The effectiveness of the approach is demonstrated by comparison with experimental data.

Design and Test of a Stress-Dependent Compensator for Magnetostrictive Actuators

Magnetostrictive transducers are employed for several purposes where, often, the applied mechanical stress strongly affects the device hysteretic behavior. This issue complicates the design of controllers where such variable has to be considered as an additional input. Nevertheless, a compensation scheme with two input variables can be defined and fruitfully utilized in a suitable invertibility region. Aim of this paper is to present a novel compensation algorithm able to take into account the applied mechanical stress. Numerical results compared with experimental data, over a magnetostrictive actuator, show that the proposed approach leads to lower compensation errors with respect to stress-independent, classical, compensators.

Experimental properties of an efficient stress-dependent magnetostriction model

In this paper a generalization of a stress-dependent magnetostriction phenomenological model is presented. The model makes use of a classical Preisach operator and of a memoryless bivariate function and includes a pure elastic contribution. It is shown that, even if the structure of the model is simple, the operator state is still influenced by the applied stress. This property is important because the model is able to catch real magnetostrictive behavior in the presence of complex time evolutions of both the variables, current and stress. Experimental and numerical results confirm the effectiveness of the proposed approach.