Supercoiled polymer (SCP) actuators belong to a recently discovered class of artificial muscles that show strong promise in various robotic applications. Extensive studies have been conducted on various aspects of SCP actuators, including the characterization of their hysteresis nonlinearity and dynamical behaviors. However, the existing strategies cannot effectively capture the first cycle of SCP actuators, which, under the application of certain sequences of inputs, gives rise to a “lonely stroke”. For example, under the application of continuous voltage oscillation sequences, the first output cycle is different from the successive repeatable cycles. This lonely stroke behavior in SCP actuators needs to be better analyzed since no comprehensive experimental investigations have been conducted. Furthermore, the lonely stroke affects SCP actuator’s performances in repeatable cycles. In this study, we conduct experimental investigations on SCP actuator’s lonely stroke under different loading and temperature conditions. The experimental procedures and measurements are presented and discussed. The results show that the coupling between lonely stroke and hysteresis is complex and history-dependent. For example, the maximum output strain discrepancy due to the lonely stroke was found to be 3.5% for an SCP actuator with a maximum strain of 15%.
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