Small-Strain Soft Robots with Distributed Magnetic Sensing

Soft robots with small-strain deformation characteristics exhibit subtle yet functionally significant shape changes, enabling precise manipulation and interaction in constrained or delicate environments. These minimal deformations pose unique challenges for sensing, requiring high-resolution, low-noise detection methods to capture motion and interaction. To address this, we investigate a distributed magnetic sensing approach tailored for small-strain soft robotic systems. Magnetic sensing offers excellent integration potential, broad detection ranges, and is well-suited for tracking fine deformations without the need for soft-material substrates. In this chapter, we present a Soft Farfield Magnetic Origami (SoMO) system that integrates a compact Hall sensor array into soft pneumatic origami actuators. The sensory array is strategically distributed to capture the distal displacement of the actuator. Through a model-based perception framework, this distal measurement is used to reconstruct multimodal spatial behaviors, including precise linear and omnidirectional bending, as well as interactive force feedback. By establishing analytical mappings between the distal position, internal pressure, and target sensing modalities, we achieve high-fidelity perception of spatial kinematics and force interactions. Our results demonstrate the capability of the proposed system to detect small-scale deformations with root-mean-square deviations of 0.36 mm in displacement, 0.02 rad in angular bending, and 0.89 N in interactive force. This methodology, from modeling and design to fabrication and validation, supports closed-loop control and fine-tuned interactive behavior in soft robots operating under small-strain deformation features.