Design and Modeling of Soft Small-Strain Actuators

Elastomers with hyperelastic deformation bring prosperity to soft robotics, especially in constituting fluidic actuators, largely due to the merit of large deformation and airtightness. However, the large (typically 0.5–1.5 strain) in-plane stretching of such materials concurrent to motion generation inevitably causes energy loss, hinders force output and accuracy. Particularly, the high nonlinearity of the low-durometer (typically 10A to 30A Shore) hyperelastic elastomers makes the modeling and control of actuators a well-known challenge. We proposed an alternative approach of using semi-rigid elastomer of significantly larger durometer (70A to 100A) to create the typical fluidic soft actuator with axial translation, by utilizing small-strain folding to generate motion. Systematic analyses on the principles, modeling and design are presented. The implementation of the SSF actuators in the soft robotic systems show high potentials in enabling high-performance soft actuators that are easy to design, fabricate and drive, strong to use, and accurate to control, towards even wider applications.