A Self-Reconfigurable Variable-Stiffness Soft Robot Based on Boundary-Constrained Modular Units

This article describes a soft robot based on boundary constrained modular subunits. The loop-shaped robot consists of a granule-filled elastic toroidal membrane with a series of modular subunit robots attached to its exterior. The robot can operate both as a soft robot to conform to external objects or navigate through narrow corridors and as a rigid robot by jamming its internal granules using a vacuum. The jammed state is useful for exerting forces on the environment in object manipulation or locomotion tasks. This article describes the robot’s design, object handling capabilities, locomotion, shape formation, and ability to navigate narrow corridors. We also present computationally efficient control methodologies used for self-reconfiguration and target tracking, which enable scaling the number of subunits to create larger systems. The robot’s scalability and the control methodologies are verified through simulation with ProjectChrono, a multibody dynamic simulation platform. All other results are obtained experimentally.