Characterization, modeling, and control of Ni-Ti shape memory alloy based on electrical resistance feedback

Abstract

The use of shape memory alloy actuators has steadily increased within the fields of aerospace, robotics, and biomedical engineering due to their superior properties compared to other actuation systems. Position control of shape memory alloy actuators is difficult due to the highly non-linear behavior but has been well studied using numerous approaches. Electrical resistance can be used to estimate strain in shape memory alloy actuator wire due to a correlation between the two parameters. Previous models of this correlation are subject to one or more drawbacks such as being limited to a single applied load, not accounting for hysteresis effects, or applying only to a specific actuator size. This article presents a stress–strain–resistance model that accounts for varying applied load, major and minor hysteresis effects and is normalized in terms of actuator geometry. Results of simulation and a simple position control experiment are demonstrated, validating the performance of the model. Furthermore, a correlation between the model and an augmented version of the Liang and Rogers model is also presented.