Configuration Design and Dimensional Optimization of a Novel Decoupled Passive Parallel Supernumerary Robotic Limb for Grinding Operations

Abstract To reduce the labor load on workers' arms during high-intensity grinding operations and mitigate the risk of work-related musculoskeletal disorders, a novel decoupled passive parallel supernumerary robotic limb (DPPSRL) is proposed in this paper. First, the configuration of the DPPSRL is designed on the basis of the requirements of typical grinding operations. The robotic arm part adopts a parallel mechanism as its kinematic configuration and employs a passive balancing mechanism to support the gravitational load of the grinding tool. The decoupling joint effectively separates the grinding reaction forces and torques, and the results of the decoupling analysis demonstrate its efficacy in reducing the arm load. Subsequently, using the arm angles to characterize the redundant degrees of freedom and configurations of the arms, the kinematic model of the human-robot parallel mechanism (comprising both the active human arms and the passive DPPSRL) is established. On this basis, a human-robot cooperative index is proposed to optimize the dimensional parameters of the handle and robotic arm part's rods. The performance analyses indicate that the parameter-optimized DPPSRL can meet the common workspace requirements and provide sufficient translational and rotational operational dexterity for handheld grinding and tool delivery tasks.