A spray-cooling based antagonistic SMA actuator (SCASA) with low resistance consumption and high driving frequency

Owing to the large strain output and high power-to-weight ratio, using temperature-induced shape memory alloy (SMA) springs in the form of antagonistic actuators offers the opportunity to develop simple, lightweight, and multi-mode robotic systems. Currently, the capabilities and deep application of these robotic systems are hindered by the relatively large resistance consumption and limited driving frequency of the antagonistic SMA actuators, primarily attributed to the cooling rate of SMA. In this paper, a spray-cooling based antagonistic SMA actuator (SCASA) was proposed, aiming to address the existing challenges in antagonistic SMA actuators. Theoretical modeling of the SCASA was comprehensively investigated. Experimental findings highlight the superior cooling efficacy of the spray-cooling method, attaining a cooling rate surpassing 100 °C per second for a single SMA spring. Using the spray-cooling based method, the driving frequency of a single SMA spring is approximately twice that of the forced-air cooling method. Experimental results also demonstrate the superior performance of the SCASA using the spray-cooling method, resulting in a reduction of approximately 50% in resistance consumption and an increase of approximately 40% in driving frequency compared to the forced-air method. This work elucidates the promising application prospects of the spray-cooling method in SMA actuators.