Shape memory alloys are among the highly applicable smart materials that have recently appealed to scientists from various fields of study. In this article, a novel shape memory alloy actuator, in the form of a rod, is introduced, and an adaptive model predictive control system is designed for position control of the developed actuator. The need for such an advanced control system emanates from the fact that modeling and controlling of shape memory alloy actuators are thwarted by their hysteresis nonlinearity, dilatory response, and high dependence on environmental conditions. Real-time identification and dynamic parameter estimation of the model are addressed according to orthogonal Laguerre functions and recursive least square algorithm. In the end, the designed control system is implemented on the experimental setup of the fabricated shape memory alloy actuator. It is observed that the designed control system successfully tracks the variable step and sinusoidal control references with startling accuracy of ±1 μm.
Shape memory alloys (SMA) are excellent candidates for implementation in actuator systems due to their ability to recover their original shape after high-strain loading through a thermally-induced phase transition. In this work, we propose and develop a novel SMA-metamaterial actuator which is capable of exhibiting a reversible, global elongation in multiple directions induced by the unidirectional contraction upon heating of a single SMA component. This actuator consists of i) an SMA component, ii) a bias component and iii) the metamaterial geometry, with each component having a distinct function: i) actuation activation, ii) reversibility of actuation upon deactivation and iii) amplifying and re-directing the uni-directional SMA actuation globally throughout the actuator, respectively. A prototype actuator was designed and tested in various configurations over multiple activation/deactivation cycles in order to demonstrate the functionality and reusability of this system. Furthermore, a theoretical model which predicts the actuation stroke of the system on the basis of the material properties of the SMA and bias components as well as the geometry of the metamaterial system was developed and validated. The findings of this work demonstrate the considerable potential of SMA-metamaterial actuators for implementation in systems requiring a multi-axial actuation output.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.