Yves Bernard

Dynamic hysteresis modeling based on Preisach model

A method to model dynamic hysteresis is proposed. The proposed model is based on an inverse Preisach model with the magnetic flux density and its rate as inputs, and the magnetic field as the output. Assuming that the hysteretic behavior does not depend on the history of this rate, the inverse distribution function is expressed in terms of the magnetic flux density rate. As a consequence, the classical utilization rules of the Preisach triangle can be applied, thus making the implementation of the proposed model very easy and efficient. The proposed model has been experimentally validated and compared with a classical static Preisach model. Since the inputs of the proposed model are the magnetic flux density and its rate, this model can very easily be implemented in a finite-element method solver using the magnetic vector potential as unknown.

A traveling wave piezoelectric beam robot

In this paper, the operation principles of a traveling wave piezoelectric beam robot are presented. A prototype consisting of an aluminum beam structure, with two non-collocated piezoelectric patches bonded on its surface, was fabricated and tested to demonstrate the generation of a traveling wave on the beam based on the one mode excitation and the two mode excitation operation principles for propulsion. A numerical model was developed and used to study and optimize the generated motion of the piezoelectric beam robot. Experimental characterization of the robot for the two types of operation has been carried out, a comparison between them is made and results are given in this paper.

A two dimensions modeling of non-collocated piezoelectric patches bonded on thin structure

Abstract The system studied in this paper consists of thin structure with several piezoelectric patches bonded on its surface. The patches are used as actuators and sensors. Based on Kirchhoff-Love hypothesis, linear constitutive relations, plane stress formulation and Hamilton principle, we have developed a 2D model for this system using the finite element method. It is not a standard 2D model, since the calculation is performed on a structure that does not have symmetries that allow such easy assumptions. The originality of the work consists in the use of the concept of neutral plane to model this asymmetric system in 2D. This technique, beside good precision, saves computational time. An experimental device has been also built and tested to validate the model. The structural damping is included in the model to match the damping behavior of the real system. Optimizations of the thickness of piezoelectric patches and materials used in the thin structures are also presented in the paper.

Determination of the distribution function of Preisach’s model using centred cycles

A new method for the determination of the classical Preisach’s model distribution function is developed. The proposed method determines numerically the distribution function from classical experimental measurements and does not make any assumption concerning the material type. The Preisach’s triangle is discretised in a finite set of cells (about 200 cells are needed). Two ways for the determination of the discretised distribution function are presented. The first assumes constant distribution function value in each cell. The second determines the nodal values of the discretised distribution function and uses a bilinear interpolation technique to obtain the distribution function in any position of the Preisach’s triangle. We also show that the proposed method can also be used to model the inverse distribution function. The comparison between modelled and experimental hysteresis curves for both major and minor cycles have shown the effectiveness of the proposed method.

Dual piezoelectric beam robot: The effect of piezoelectric patches’ positions

Inspired from linear traveling wave ultrasonic motors, a dual piezoelectric beam robot is presented. It consists of an aluminum beam structure, with two non-collocated piezoelectric patches bonded on its surface. The aim of this article is to study the effect of the piezoelectric patches’ positions on the performance of the robot. For a given robot dimension, a finite element model developed in a previous work for the robot structure is verified experimentally here and then used to determine the optimal piezoelectric patches’ position. It has been found that locating the piezoelectric patches near the ends of the beam will lead to best performance, and that the traveling wave is mainly generated between the two patches. Two prototypes have been manufactured for this aim and have shown good agreement with simulation results.

Modeling of a beam structure with piezoelectric materials: introduction to SSD techniques

Purpose – To provide a model that allows testing and understanding special damping techniques. Design/methodology/approach – The finite element modeling takes into account the piezoelectric coupling. It is used with a non linear electrical circuit. The approach leads to an accurate tool to observe the behavior of the non linear damping techniques such as synchronized switch damping. Findings – The model has been validated by comparison with Ansys® but the CPU time required for the model is around one hundred times shorter. Research limitations/implications – The proposed model is 1D and the assumptions to use it are not verified for all structures. Practical implications – The authors obtain a useful tool for the design of damping structures (for example to find the best localisation of the piezoelectric patches and to test electrical circuits). Originality/value – The model is used for the design and conception of damping as well as for harvesting structures.

Modeling of a Plate Structure With Piezoelectric Patches: Damping Application

Vibrations in thin structures are often not desired, especially because of their harmful effects on lifespan. The addition of piezoelectric materials with appropriate connections can really be useful to reduce this drawback. To study such a damping effect, numerical modeling is necessary and leads to a coupled problem (between mechanics and electricity). This paper presents a 2-D model of a plate with piezoelectric patches. From the coupled behavior laws and with the use of a variational formulation, a finite element model is developed. After a validation process, the influence of the width of piezoelectric patches on damping is studied.

Design and manufacturing of a piezoelectric traveling-wave pumping device

In this article, we present the design and construction of a micropump exhibiting a nontraditional pumping principle whose design is achievable at very low scales. The operation is based on the action of a mechanical traveling wave deforming the bottom wall of a flexible channel containing a fluid. The paper treats for the first time the influence of the traveling wave parameters on the performance of the pump with the help of finite element simulations. The results obtained from the simulation are subsequently used for the dimensioning of the linear ultrasonic traveling wave actuator that drives the device. Finally, a very simple channel-reservoirs structure was conceived to test the device. At this point, several measurements of flow rate and back pressure were carried out to estimate the performance of the prototype for different values of wave amplitude. The article finishes with a comparison between the numerical and experimental results and a brief section of discussion and conclusions.

Study of the influence of leakage fields on the inchworm actuator

In this paper, we study the design parameters and especially the influence of leakage electric fields on the performance of a piezoelectric inchworm actuator. We consider the total deformation of the actuator and the first piezoelectric element capacitance as a good indication of the leakage fields produced in the insulators. Particularly, we study the effect of the thickness of insulating disks that separate the piezoelectric elements and the effect of the state of central element electrodes when unexcited. The result of a coupled electromechanical modeling is that the leakage field does not have an important effect for this device geometry.

EMC analysis of MRI environment in view of optimized performance and cost of image-guided interventions

In this work an electromagnetic compatibility (EMC) analysis is performed by means of a dedicated finite element simulation of magnetic resonance imaging (MRI) environment to determine the impact of hosting in the scenery different materials and structures necessitated in guided interventions. The results obtained by simulation could be used for the design and optimization of devices used in such environment (actuator, mechatronics...).