Bidirectional Optical sensors for Actuation Tracking (BOAT) in soft lattice systems

2026-05-18

AI Summary

This study addresses the lack of high-precision, distinguishable bidirectional deformation sensing in soft lattice robots undergoing compression and extension. The authors propose BOAT, a dual-patterned optical waveguide sensor based on ellipsoidal geometric arrangements, co-printed with pneumatic artificial muscle–actuated lattice structures. By monitoring intensity changes in light transmission induced by waveguide bending, the system enables real-time identification of bidirectional deformation states. This work presents the first demonstration of monolithic co-printing of soft lattices integrated with bidirectional optical sensors, facilitating the development of synchronized digital twin systems. Experimental results show that under cyclic pressure loading of ±50 kPa, the system reliably distinguishes between tensile and compressive states with high repeatability, successfully realizing a physically-virtually synchronized digital shadow.

Abstract

The growing adoption of lattice-based structures in soft robotics creates a need for advanced sensing solutions capable of monitoring their global deformation, particularly compression and extension. In this work, we address this challenge by introducing a novel optical sensor based on two patterned waveguides arranged in an ellipsoidal geometry. This Bidirectional Optical sensor for Actuation Tracking (BOAT) is seamlessly co-printed with a lattice structure actuated by an embedded pneumatic artificial muscle (PAM), and its performance is assessed. During PAM elongation or contraction, the bending of the embedded BOAT waveguides induces output signal variations that enable a clear discrimination between compression and extension states. The designs of both each specific waveguide structure (by surface patterning) and of the sensorized lattice-based unit embedding two BOATs are supported by numerical simulations. Experimental calibration over 100 consecutive pressure cycles ranging from +50 kPa to $-$40 kPa demonstrates a highly repeatable response, allowing a reliable distinction between extension and compression. Finally, sensor feedback is used to implement a digital shadow, enabling continuous synchronization between the whole sensorized unit and its virtual counterpart. These results establish BOAT as a powerful and reliable approach for deformation monitoring in soft lattice-based robotic systems.

Problem

• soft robotics
• lattice structures
• deformation sensing
• compression and extension
• optical sensors

Innovation

• bidirectional optical sensing
• soft robotics
• lattice structures
• digital shadow
• co-printed sensors