Harnessing the nonlinear properties of buckling inflatable tubes for complex robotic behaviors

Abstract

Imparting complex behaviors to soft robots generally entails complex designs and carefully engineered structures. As such, making soft structures with behaviors such as stiffening, bistability and rapid snapping deformations generally requires specialized solutions. This work introduces the use of short inflatable tubes that buckle under compression to realize behaviors such as self-stiffening, bistability and snap-through induced rapid deformations. These inflatable tubes have a nonlinear behavior resulting from these tubes having two stable states, the buckled and unbuckled states, and the complex transition between states which entails a snap-through buckling instability during the buckling transition, and a range of deformation where the tube is bistable as it is stable in either the buckled or unbuckled states. This work shows how the dimensions of the inflatable tubes affect this behavior and proposes a numerical model that can describe the entire cyclic behavior of buckling and unbuckling inflatable tubes. It is then demonstrated how simply connected multiple inflatable tube segments in series can be used to produce complex robotic behaviors. A soft robotic hand is demonstrated that uses the characteristics of unbuckling inflatable tubes for self-stiffening, and a grasping tool capable of slow or rapid motions by making use of the ability of serially connected inflatable tubes to transition from bistability to monostability.

See full text for more information.