Challenges for practical applications of shape memory alloy actuators

Shape memory alloy (SMA) actuators present opportunities for the development of novel actuating systems. High force-to-weight ratio, silent operation, muscle-like motion, biocompatibility, and simple design possibilities have attracted researchers to SMA actuators. Many SMA actuated systems in engineering and medical domains have been reported in the literature. Recently, SMAs have also being used to develop soft robotic systems. However, low absolute force and high cycle time have limited the widespread use of these actuators. Moreover, non-linear and unpredictable behaviour caused by hysteresis results in difficulties to accurately control it. Some work detailing the strategies to overcome these shortcomings has been reported in the literature, this paper presents an articulated brief review of the techniques to overcome low force, long cycle time, and material non-linearity issues.