RTSRAs: A Series-Parallel-Reconfigurable Tendon-Driven Supernumerary Robotic Arms

Supernumerary robotic limbs (SRI) are new types of wearable robots used as the third limb to work with humans. The device is designed to provide the wearer with better auxiliary ability. This paper presents the design and implementation of a Series-Parallel-Reconfigurable Tendon-driven Supernumerary Robotic Arms (RTSRAs), which is lightweight, compact and Multi-assistive for the wearers. Existing Supernumerary robotic limbs (SRL) almost use series configurations with high flexibility, but relatively poor carrying capacity compared to parallel configurations. Balancing the contradiction between load capacity and flexibility, we propose a Series-Parallel-Reconfigurable configuration requiring clever end-conversion tools to better adapt to variable tasks. To achieve the compactness of RTSRAs, two kinds of tendon-driven joint module were designed. The coupled tendon-driven joint module was applied to transmit the power of motors mounted near the backboard to the elbow joints, which greatly reduce the motion inertia and increase load capacity of RTSRAs. Finally, on the basis of forward and inverse kinematics analysis, we make the evaluation of RTSRAs. The proposed RTSRAs has been successfully applied in typical load operation scenario and suggests a great potential in future applications.