Shape Memory Alloy Actuator for Artificial Muscle

摘要

In the present study we attempted to develop an actuator that is comparable to a natural muscle in terms of flexibility, output force and responsiveness. In an earlier report we presented the Shape Memory Alloy (SMA) actuator protected by “a rolled film tube” that exhibited high heat resistance and high flexibility, and termed it “the unit cell”. In the present study, we developed an actuator dubbed “a motor unit” exhibiting a larger output force by bundling 7 unit cells together, and investigated the characteristics of this motor unit in experiments where the motor unit was driven by Pulse Frequency Modulation (PFM). The results of the experiments indicate that the static characteristics of the output force and the displacement due to the input pulse frequency in the motor unit are proportionate in comparison to the unit cell, and that the output force is nearly 7 times greater than that of the unit cell. Results also indicate that the time constant of the motor unit increases compared to that of the unit cell, and power conversion efficiency decreases when pulse width is extended to improve the time constant.