Design, Fabrication and Control of an Octopus-inspired Underwater Soft Robot

Abstract

Rising environmental pressures in aquatic ecosystems due to climate change require robotic systems capable of safe and non-invasive operation. Conventional underwater robots are typically rigid and rely on noisy, high-power actuators, limiting their suitability for sensitive environments such as coral reefs, seagrass meadows, and freshwater lakes and rivers. Here, we present an octopus-inspired robot integrating a hybrid rigid-soft body with compliant tentacle actuation and closed-loop navigation control. Central to the design is an experimental characterization of the actuator force–angle relationship, which enables a model-based feedforward strategy that exploits a locally linear operating regime, avoiding the computational burden of full nonlinear modeling. This feedforward component is combined with proportional–derivative (PD) feedback control to reject disturbances and compensate for model mismatch. The robot achieves an average forward velocity of 0.072 m/s under open-loop operation. Turning experiments show that maneuverability is governed by torque generation, achieving a minimum turning radius of 0.221 m using two-arm actuation. Closed-loop target tracking demonstrates robust navigation under disturbances through integrated vision- and inertial-based state estimation and task-level actuation allocation. Together, these results demonstrate that bio-inspired morphology combined with experimentally grounded hybrid control can yield efficient, adaptive platforms for underwater operation in ecologically sensitive environments.