Design and Control of a Soft Supernumerary Robotic Limb Based on Fiber-Reinforced Actuator

Supernumerary robotic limbs (SRLs) provide additional wearable limbs to enhance the user's physical abilities. Most SRLs employ rigid structures, resulting in uncomfortable wearing experience and insufficient flexible manipulation. As a new type of SRL, soft SRLs offer operational flexibility, lightweight structure, and wearing safety, compensating for the shortcomings of rigid SRLs. However, due to the complex actuation mechanisms, soft SRLs pose challenges in multiple deformations and accurate controlling. In this paper, a soft SRL actuated by fiber-reinforced actuators (FRAs) is proposed. A kinematic model is established to capture the posture of the SRL. A control system is proposed to adjust the SRL posture precisely by configuration of the FRAs. Finally, the accuracy of the proposed control strategy is verified through experiments, and the SRL prototype exhibits flexibility and adaptability to various scenarios, effectively assisting users in accomplishing complex tasks.