A nonlinear model for ferromagnetic shape memory alloy actuators

Ferromagnetic shape memory alloys (FSMAs) such as Ni–Mn–Ga have attracted significant attention over the last few years. As actuators, these materials offer high energy density, large stroke, and high bandwidth. These properties make FSMAs potential candidates for a new generation of actuators. The preliminary dynamic characterization of Ni–Mn–Ga illustrates evident nonlinear behaviors including hysteresis, saturation, first cycle effect, and dead zone. In this paper, in order to precisely control the position of FSMA actuators a mathematical model is developed. The Ni–Mn–Ga actuator model consists of the dynamic model of the actuator, the kinematics of the actuator, the constitutive model of the FSMA material, the reorientation kinetics of the FSMA material, and the electromagnetic model of the actuator. Furthermore, a constitutive model is proposed to take into account the elastic deformation as well as the reorientation. Simulation results are presented to demonstrate the dynamic behavior of the actuator.