Irreversible thermodynamics and smart materials systems modelling. Example of magnetic shape memory actuators.

International audienceSmart systems is a very promising technology to design high performance and highly integrated mechatronic devices. Nevertheless, one of the main drawbacks of these devices is the complex non-linear and irreversible behaviour of the active materials at the heart of such systems. To solve these difficulties, this paper presents a thermodynamics based procedure to model more accurately active materials. After a review on energy conversion modeling techniques, the paper extends classical thermodynamics procedure to the case of irreversible processes. The use of internal state variables helps to improve the physical understanding of non-linear and irreversible mechanisms in smart materials. This procedure is applied to Magnetic Shape Memory Alloys actuators and the results are quite encouraging. Modelling methods proposed in this paper improves the understanding of complex active materials for smart systems

Port hamiltonian modeling of MSMA based actuator: toward a thermodynamically consistent formulation.

International audienceThis paper presents a thermodynamically consistent model of MSMA (Magnetic Shape Memory Alloys) under port Hamiltonian framework. It is based on previous works on MSMA proposed in (Gauthier et al., 2008; Calchand et al., 2011). The main di erence lies in the choice of the state variables and manipulated thermodynamic forces. Furthermore in (Gauthier et al., 2008), subsequent experiments revealed a highly hysteretic behavior of these materials. Here, the simpli ed hysteretic behavior is incorporated into the port-hamiltonian model to obtain a ner and more precise model. Such modeling will allow the use of a wide range of energy based methods to design the associated control system. The paper ends with some extensions to more complex hysterestic phenomena by using Preisach like model. First ideas are proposed to extend the previous physical model to systems with internal hysteretic loops

From canonical Hamiltonian to Port-Hamiltonian modeling application to magnetic shape memory alloys actuators.

International audienceThis paper presents the modelling of an actuator based on Magnetic Shape Memory Alloys (MSMA). The actuation principle relies on the ability of the material to change its shape under the application of a magnetic field. Previous models proposed by authors were based on canonical (symplectic) Hamiltonian modeling and thermodynamics of irreversible processes. These models, though physically cogent, are non-minimal differential algebraic dynamical models and hence less adapted for control purposes.This paper therefore proposes a modified and systemoriented modeling procedure which lends itself naturally to a port-Hamiltonian model. The latter is found to be a minimal realization of the above whereby interconnection between subsystems is clearly visible. Using Lagrange multipliers, constraints which arise due to causality and interconnection are expressed. In the last section, Differential Algebraic Equations (DAE) resulting from previous models are reduced to Ordinary Differential Equations (ODE) and by using coordinate transformations, constraints are decoupled from the system input/output. The resulting model is well-suited for control

Modelisation et commande des alliages à mémoire de forme magnétique dans le cadre des hamiltonien à port s

Active materials are a class of material which react to an external stimulus such as temperature,photons, magnetic field or electric field. These stimuli cause some properties of the material tochange usually their length. Some examples are piezoelectric material which change their lengthunder the action of an electric field, Shape Memory alloys which alter their shape on applicationof heat, and more recently Magnetic Shape Memory Alloys (MSMA) which undergo a deformationon application of a magnetic field. Harnessing this property of MSMAs, we hereby present anactuator using this novel material. We extensively make use of an energy framework, namely thethermodynamics of irreversible processes to model the material. This framework has been provento be very versatile in modelling energy exchange and transformation as it occurs in the materialand also to incorporate hysteresis which arises naturally in such materials. Another advantage of thismethod is its ability to give us constitutive laws based on simple assumptions. Furthermore, usingan energy framework allows us to apply some energy based control. Port Hamiltonian Control is onesuch method and it is not limited only to linear models. This latter characteristic has proven veryuseful since MSMAs are very non-linear in nature.Les matériaux actifs sont des matériaux qui réagissent quand on leur applique un champ extérieur comme la température, la lumière, un champ magnétique ou un champ électrique. Ces champs changent les propriétés du matériau comme la longueur, la susceptibilité magnétique ou la permittivité électrique. Ces changements peuvent être utilisé pour faire du travail. Quelques exemples sont les matériaux piézoélectriques, qui changent de longueur quand on applique un champ électrique, les alliages à mémoire de forme qui changent leur longueur sous l’action de la température. Un matériau plus récent qu’on appelle les alliages mémoire de forme magnétique se de forme sous l’action d’un champ magnétique. Dans cette thèse, on utilise ce matériau pour Confectionner un actionneur. Pour ce faire, on utilise la thermodynamique des procédés irréversibles pour modéliser le matériau. La thermodynamique s’avère très versatile pour ce type de matériau car il permet de quantifier l’ échange et la transformation d’ énergie dans le matériau. Aussi, étant donné que le matériau se comporte d’une façon non-linéaire et hystérique, le cadre énergétique nous permets justement de prendre en compte ces non- linearités. Cette thèse utilise l’approche énergétique notamment les Hamiltonien à ports pour modéliser un actionneur à base d’alliage à mémoire de forme. Cette méthode nous permets aussi de concevoir des lois de commande pour contrôler le matériau

Modélisation et commande d'alliages à mémoire de forme magnétique basés sur le formalisme des port-hamiltoniens.

Active materials are a class of material which react to an external stimulus such as temperature,photons, magnetic field or electric field. These stimuli cause some properties of the material tochange usually their length. Some examples are piezoelectric material which change their lengthunder the action of an electric field, Shape Memory alloys which alter their shape on applicationof heat, and more recently Magnetic Shape Memory Alloys (MSMA) which undergo a deformationon application of a magnetic field. Harnessing this property of MSMAs, we hereby present anactuator using this novel material. We extensively make use of an energy framework, namely thethermodynamics of irreversible processes to model the material. This framework has been provento be very versatile in modelling energy exchange and transformation as it occurs in the materialand also to incorporate hysteresis which arises naturally in such materials. Another advantage of thismethod is its ability to give us constitutive laws based on simple assumptions. Furthermore, usingan energy framework allows us to apply some energy based control. Port Hamiltonian Control is onesuch method and it is not limited only to linear models. This latter characteristic has proven veryuseful since MSMAs are very non-linear in nature.Les mat´ eriaux actifs sont des mat´ eriaux qui r ´eagissent quand on leur applique un champext ´ erieur comme la temp´ erature, la lumi`ere, un champ magn´etique ou un champ ´ electrique. Ceschamps changent les propri ´ et ´es du mat´ eriau comme la longueur, la susceptibilit ´e magn´etique oula permittivit ´e ´ electrique. Ces changements peuvent ˆ etre utilis ´e pour faire du travail. Quelquesexemples sont les mat´ eriaux pi ´ezo´ electriques, qui changent de longueur quand on applique unchamp ´ electrique, les alliages `a m´emoire de forme qui changent leur longueur sous l’action de latemp´ erature. Un mat´ eriau plus recent qu’on appelle les alliages `a m´emoire de forme magn´etiquese deforme sous l’action d’un champ magn´etique. Dans cette th `ese, on utilise ce mat´ eriau pourconfectionner un actionneur. Pour ce faire, on utilise la thermodynamique des proc´ed´es irr ´eversiblespour mod´ eliser le mat´ eriau. La thermodynamique s’av`ere tr `es versatile pour ce type de materiaucar il permet de quantifier l’ ´echange et la transformation d’ ´energie dans le mat´ eriau. Aussi, ´ etantdonn´e que le materiau se comporte d’une fac¸on non-lin ´ eaire et hysteretique, le cadre ´energetiquenous permets justement de prendre en compte ces non-linearit ´es. Cette th `ese utilise l’approche´energ´etique notamment les Hamiltonien `a ports pour mod´ eliser un actionneur `a base d’alliage `amemoire de forme. Cette m´ethode nous permets aussi de concevoir des lois de commande pourcontr ˆ oler le mat´ eriau