Underwater soft robotic open-loop control for disturbance rejection using stiffness and camber control.

Disturbances in for the form of gusts, wakes, and waves are a challenge faced by swimming robots. They can have impacts on trajectory control and also cause damage to robots and the subsea environment when collisions occur. In this work, we present a soft robotic foil with built-in stiffness and camber control and integrated eSkin for deformation feedback. The stiffness and camber is controlled using internal pressurised elastic tubes. The eSkin works by measuring the relative capacitance signals of embedded liquid metal wires. The soft robotic foil was placed in a flow channel and up to 100% lift disturbances were induced through a positive or negative change in angle of attack. We show that open-loop control with scheduled camber and stiffness change is able to reduce the effects of a 10 convective cycle disturbance by 90%. We demonstrate the use of eSkin deformation feedback for closed-loop camber set point control for a soft robot. We aim to use this to achieve closed-loop soft robotic disturbance rejection without the need for force feedback.