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

TL;DR

This paper introduces BOAT, a novel optical sensor integrated with soft lattice structures, capable of reliably monitoring deformation states like compression and extension through waveguide bending signals.

Contribution

The work presents a new optical sensing method co-printed with soft lattice robots, enabling real-time deformation tracking with high repeatability and digital synchronization.

Findings

BOAT can distinguish between compression and extension states.

Experimental calibration shows high repeatability over 100 pressure cycles.

Sensor feedback enables continuous synchronization with a virtual model.

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.