A Bio-Inspired Scalable Parallel Actuation Approach for Modular Reconfigurable Supernumerary Limbs

Supernumerary Robotic Limbs (SRLs) offer considerable promise for assisting wearers in complex tasks, yet their adaptability is often constrained by their inherent fixed morphology. While modular reconfigurable designs present a viable solution, applying it to wearable systems introduces critical size-payload trade-offs. To address these limitations, this letter, drawing inspiration from the human upper limb, introduces a modular reconfigurable supernumerary robotic limb (MRSRL) based on a tightly integrated hardware and control co-design. At the hardware level, we developed a novel joint module featuring a bio-inspired redundant actuation mechanism. The module's partitioned design also ensures functional extensibility. At the control level, we designed a unified control framework leveraging active disturbance rejection control to effectively suppress backlash and maintain robust motion tracking across heterogeneous actuator configurations. Experimental validation demonstrates the system's efficacy, achieving a 4.21-fold increase in torque-to-weight ratio compared to the single-motor module, and reductions of 7.20% and 17.34% in maximum absolute error and integral of absolute error, respectively, against baseline methods. Our work establishes a robust framework for the development of next-generation SRLs capable of adapting to a wide range of tasks.