A soft rotary actuator with a flexible shaft using flexible pneumatic actuators

This paper proposes a soft rotary actuator that can rotate even when its shaft is bent. The tested rotary actuator consists of three Extension-type Flexible Pneumatic Actuators (EFPA), flexible plates for restraining the EFPAs geometrically, and a polyurethane tube as a shaft. The EFPA consists of a silicone rubber tube covered with a sleeve that can expand significantly in the axial direction when the tube is pressurized. By restraining the EFPA to a helical shape using plates, the proposed rotary actuator can rotate when the three EFPAs are extended in the rotational direction upon the application of pressure. It is confirmed that the tested actuator could rotate even if the shaft is bent, because the shaft and EFPAs consist of flexible materials. The maximum rotation angle and torque are approximately 400° and 0.5 Nm, respectively, for an input pressure of 500 kPa. An analytical model of the tested actuator is proposed to predict the relationship between the rotation angle and the input pressure. A comparison between the calculated and experimental rotation angles reveals that the experimental results can be accurately predicted using the proposed analytical model, which considers the effects of EFPA friction and restraining.

© 2023 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/

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