Analytical modeling for design and performance evaluations of a new low aspect ratio soft rotary pneumatic actuator

Abstract This paper presents a different type of rotary actuator in contrast to conventional rotary actuators that operate by fiber wound in the form of a helix on a cylinder-shaped elastomer. Our actuator has a fiber set placed in the rθ plane of an elastomer in the form of an annulus, this elastomer expands under pneumatic pressure input to deliver rotation and torque to a rigid shaft connected to the elastomer’s inner circumference. In addition to the description and testing of our actuator’s novel mechanism, the main contribution of this paper is the design’s verification through a theoretical analysis of the rotational motion generated by the mutual influence of the elastomer and inflexible fiber elements. We also show how the design parameters are related to the wound angle of how much the fiber set inserted in the elastomer was wound in a spiral configuration. For various wound angles, computer simulation and experiments were carried out to prove the validity of our analytical model. Further experiments were conducted to measure the performance of the actuators by conducting a torque test with rotation set to zero.