A Hybrid Underwater Manipulator System with Intuitive Muscle-Level sEMG Mapping Control

Soft-robotic manipulators, with their closed-chamber elastomeric actuators, natural water-sealing and inherent compliance, are ideal for underwater applications for compact, lightweight, and dexterous manipulation tasks. However, their low structure rigidity makes soft robots highly prone to underwater disturbances, rendering traditional control methods unreliable, substantially increasing the challenges for high-dexterity control. To address this issue, we proposed an intuitive underwater hybrid manipulator system with a muscle-level mapping design concept. The manipulator was designed to construct an actuator-configuration which could directly map to the main muscles group in the human forearm. Exploiting this analogy, an electromyography-based wearable controller was developed using continuous bio-sensory data from the operator's arm to complement the intuitive manipulator control. A prototype of the proposed manipulator was constructed and validated in various experiments, where a human user could effectively use muscle activations to proportionally drive the soft-robotic manipulator in free-space motions, as well as performing object manipulation tasks both in air and underwater, only using visual feedback, with consistent performances under various time delays. The promising results of this work have demonstrated that the muscle-level analogy of soft robotics could lead to intuitive and effective underwater manipulation with simple structure and low control effort.