Zero-electric-power position retaining utilizing hysteresis on an antagonistic shape memory alloy system

Abstract

Shape Memory Alloy (SMA) actuators must be continued to be heated generally to retain a shape of a smart structure deformed by the SMA actuators. To save the energy applying to the smart structure, a new control method was proposed utilizing the fact that strain is not single valued even at the same stress and temperature state due to hysteresis in stress-strain-temperature relationship of SMA. Feasibility study of the control method was performed by a fundamental experiment for an antagonistic SMA system. When a pulsed voltage was applied to one SMA, the system moved to some direction, and while the voltage was not applied to the SMA after the pulsed voltage, the system did not return to the original position and was remained at a certain position. Successively, when a larger pulsed voltage was applied to the same SMA or another pulsed voltage was applied to the other SMA, the system moved to the same direction more or the other direction, respectively, and was retained at certain positions without applying the voltages. To explain and confirm the behavior of the system, numerical simulation was also performed. The simulated result agreed with the experiment qualitatively and could explain the mechanism of the behavior. From the results mentioned above, the feasibility of the proposed control method could be shown both experimentally and numerically.