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Real-time compatible phenomenological modelling of the austenitic phase in shape memory alloys as an example for modelling of materials with repeatable non-linear characteristics

: Pai, A.; Traechtler, A.; Schaper, M.


IFAC-PapersOnLine 48 (2015), No.11, pp.1043-1048
ISSN: 2405-8963
ISSN: 1474-6670
Conference on Modelling, Identification and Control of Nonlinear Systems (MICNON) <1, 2015, Saint Petersburg>
Journal Article, Conference Paper
Fraunhofer IPT ()

Shape Memory Alloys (SMAs) are attractive materials for a variety of applications due to advantages such as high reversible strains, high specific actuation stresses and high energy density. The extreme non-linearity inherent in SMAs, however, makes the design of applications such as position control non trivial. While control strategies benefit greatly from models incorporating these non-linearities, existing models for SMA constitutive behaviour are either too complicated to be used in real-time applications or too simple to accurately predict observed behaviour. When considering the mechanical stress-strain behaviour of austenitic SMAs, for example, it can be observed that the non-linearities follow distinct patterns. These patterns can be exploited to form mathematical models with continuous analytical functions that are extremely computationally effective and thus making it conducive for use in the development of real-time control algorithms and sophisticated indus trial applications. This work presents a method for the modelling and identification of non linear materials for control purposes given that the non-linearities are repeatable or hysteretic in nature using pseudoelastic SMAs as an example. The model is validated by stress-strain experiments and the results show good correlation with experimental data.