Anisotropic Stiffness and Programmable Actuation for Soft Robots Enabled by an Inflated Rotational Joint

TL;DR

This paper introduces an inflatable rotational joint with tunable anisotropic stiffness for soft robots, enabling programmable bending and complex actuation while maintaining structural integrity under various loads.

Contribution

It presents a novel inflatable actuation module with forced partial wrinkling for tunable stiffness and demonstrates its application in soft continuum robots.

Findings

Stiffness in the bending direction can be precisely controlled by wrinkling ratios.

The module maintains kinematic constraints across different loading conditions.

Potential for complex, decoupled actuation in soft pneumatic robots.

Abstract

Soft robots are known for their ability to perform tasks with great adaptability, enabled by their distributed, non-uniform stiffness and actuation. Bending is the most fundamental motion for soft robot design, but creating robust, and easy-to-fabricate soft bending joint with tunable properties remains an active problem of research. In this work, we demonstrate an inflatable actuation module for soft robots with a defined bending plane enabled by forced partial wrinkling. This lowers the structural stiffness in the bending direction, with the final stiffness easily designed by the ratio of wrinkled and unwrinkled regions. We present models and experimental characterization showing the stiffness properties of the actuation module, as well as its ability to maintain the kinematic constraint over a large range of loading conditions. We demonstrate the potential for complex actuation in a soft continuum robot and for decoupling actuation force and efficiency from load capacity. The module provides a novel method for embedding intelligent actuation into soft pneumatic robots.