Dynamic modeling of a new varying stress SMA actuator for precise applications

Shape memory alloys (SMA´s) are inherently non-linear devices exhibiting significant hysteresis in their stress strain-temperature characteristic. We have used the variable sub-layer SMA model of Ikuta (1991) to extract the advanced dynamic model of our proposed varying stress SMA actuator. A nonlinear finite element analysis was used to model the proposed bending spring in the actuator and the extended variable sub-laver model of Ikuta was considered to extract stress-displacement relations. Finally, these two models are combined with thermo dynamic model of SMA and a schematic flowchart is proposed to calculate SMA resultant strain under an arbitrary current input. At the end, we applied this model to extract open loop harmonic and step responses of our proposed SMA actuator.