Energy-efficient tunable-stiffness soft robots using second moment of area actuation

Abstract

The optimal stiffness for soft swimming robots depends on swimming speed, which means no single stiffness can maximise efficiency in all swimming conditions. Tunablestiffness would produce an increased range of high-efficiency swimming speeds for robots with flexible propulsors and enable soft control surfaces for steering underwater vehicles. We propose and demonstrate a method for tunable soft robotic stiffness using inflatable rubber tubes to stiffen a silicone foil through pressure and second moment of area change. We achieved double the effective stiffness of the system for an input pressure change from 0 to 0.8 bar and 2 J energy input. We achieved a resonant amplitude gain of 5 to 7 times the input amplitude and tripled the high-gain frequency range compared to a foil with fixed stiffness. These results show that changing second moment of area is an energy effective approach to tunable-stiffness robots.

Soft Robot Design, Manufacturing, and Operation Challenges: A Review

“…Wei et al [59] also looked at a flexible robot that can grip objects and has variable stiffness based on a folding plate mechanism and particle jamming. Micklem et al [210] proposed and demonstrated a method for tunable stiffness using inflatable rubber tubes to effectively stiffen a soft robot via adjusting the internal pressure of the inflatable tubes from 0 to 80 KPa.…”

A Soft Robotic Morphing Wing for Unmanned Underwater Vehicles

“…[ 7,8 ] These features ensure fewer repairs and maintenance to the wings; essential qualities in cluttered deep‐sea environments. Most of the present literature regards the use of soft robotic actuation for undulatory propulsion in marine applications, [ 9–16 ] whereas this work focuses on using soft wings to maximize efficiency in UUVs. Here, the design and manufacturing process of a wing constituted of a soft silicone actuator and a rigid leading edge are explored.…”

A Soft Robotic Morphing Wing for Unmanned Underwater Vehicles

“…[7,8] These features ensure fewer repairs and maintenance to the wings; essential qualities in cluttered deep-sea environments. Most of the present literature regards the use of soft robotic actuation for undulatory propulsion in marine applications, [9][10][11][12][13][14][15][16] whereas this work focuses on using soft wings to maximize efficiency in UUVs.…”