Soft Robots Grow a Spine: Origami-Inspired Folding Endoskeletal Support for Motion and Stiffness Control of Inflatable Robots

Abstract

We present a deployable inflatable robotic torso with an origami-inspired spine, designed to combine the inherent compliance of soft robots with the controllability of skeletal structures. Unlike simple inflatable cylinders, which deform unpredictably through membrane buckling, our approach embeds a foldable spine that defines discrete bending axes and enables repeatable motion. Pneumatic inflation provides compact self-deployment, external stiffening, and a compliant outer shell that serves as a protective contact interface, while tendon actuation delivers precise, joint-level control. Experiments demonstrate that the torso replicates and in some cases exceeds human spinal range of motion, and that combined tendon–pneumatic actuation doubles lateral stiffness compared to pneumatics alone. We further characterize stiffness–motion trade-offs across pressures, showing tunable performance relevant to contact-rich operation. This integration of origami endoskeletons with inflatable bodies advances deployable humanoid-scale robots, addressing the gap between compliant contact behavior and controlled movement.