Soft Robots Grow a Spine: Origami-Inspired Folding Endoskeletal Support for Motion and Stiffness Control of Inflatable Robots
Junil Min, Matthew Robertson
AI summary
Problem
Simple inflatable soft robots deform unpredictably through membrane buckling, lacking controlled motion and tunable stiffness. Extending soft principles to humanoid-scale torsos requires internal structures that define discrete bending axes while maintaining a compliant, deployable outer interface.
Approach
The design integrates a foldable origami endoskeletal spine within a pneumatically inflated shell, using tendon-driven actuation to define discrete bending axes and enable precise, joint-level control.
Key results
- Replicates and exceeds human spinal range of motion in sagittal and frontal planes
- Combined tendon-pneumatic actuation doubles lateral stiffness compared to pneumatics alone
- Demonstrates a tunable stiffness–motion trade-off across 70–120 kPa inflation pressures
- Achieves compact self-deployment with a 12.5% stowage ratio while maintaining repeatable joint control
Why it matters
Bridges the gap between compliant contact safety and controlled movement, advancing deployable humanoid robots for field operations, rehabilitation, and wearable assistance.
Abstract
We present a deployable inflatable robotic torso with an origami-inspired spine, designed to combine the inher- ent compliance of soft robots with the controllability of skeletal structures. Unlike simple inflatable cylinders, which deform un- predictably 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 actua- tion 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.