Structural Analysis and Design of Humanoid Arms from Human Arm Reachable Workspace

Having a workspace (postural-reachable) for the humanoid arm that is similar to a human arm around the upper body is essential for effective operation in human-like environments. However, research in this area is scarce. This letter aims to investigate the optimal structural configuration of a humanoid arm in the workspace around the upper body (WAUB). For this purpose, we initiate by analyzing the reachability data of human arm in the WAUB and subsequently propose a design strategy that incorporates this human data into the humanoid arm design. The proposed strategy consists of two key components: a structural parameter optimization method based on the postural reachability of task points and a task point identification method tailored to the WAUB. The optimization process leverages the covariance matrix adaptation evolutionary strategy (CMA-ES) and integrates collision-free control into each optimization iteration for realistic arm motion. The task point identification involves defining an expected workspace derived from human data and selecting task points through analysis of the hard-to-reach areas. Humanoid upper body models are introduced considering the anthropomorphic contour of human body and humanoid shoulder features. Performance tests conducted on these models assess the effectiveness of optimization. The results can offer practical insights for humanoid arm design.