Anthropomorphic Precision-Grasp Evaluation of a Four-Fingered Metamorphic Robotic Hand

Abstract Compared with fixed-palm robotic hands, a metamorphic anthropomorphic hand featuring a foldable palm exhibits superior grasp flexibility, enlarged workspace, and enhanced adaptability in manipulation tasks. For the two primary grasp patterns, power grasps ensure stability through large contact areas and distributed forces, whereas precision grasps—constrained by minimal contact points—inherently risk instability that may damage both objects and the robotic hand. This study conducts a systematic performance evaluation of a four-fingered metamorphic robotic hand, focusing on its precision-grasp capability through force-closure and force-balance analysis of 12 typical anthropomorphic gestures. Different from the conventional online grasp-evaluation strategies, which are limited by their reliance on predefined target objects and thus cannot fully characterize the robotic-hand's grasp performance, the evaluation methodology proposed in this study does not presuppose any specific object shapes. Instead, atlases of each gesture's grasp performance are elaborated by integrating the level of the minimum friction coefficient and the size of the grasped object, utilizing both single-metric and combined-metrics approaches. The analysis further sheds light on actuation optimization schemes for the metamorphic anthropomorphic hand.