Design concept and kinematic analysis of a compliant anatomical palm mechanism for bio-inspired robotic hand design

Abstract This paper explores the often-overlooked importance of the palm in robotic hand design, where traditional approaches emphasize finger dexterity and multi-motor manipulation to achieve diverse degrees of freedom (DOF) for grasping. The palm’s ability to conform to objects while grasping is unique due to its versatility to create different shapes. However, replicating this complex folding, bulging, and contouring of the human palm in a mechanical equivalent presents significant challenges. To address this, the paper introduces the concept of a Compliant Anatomical Palmar Mechanism (CAPM), using a combined experimental and numerical approach to model kinematic characteristics of a hybrid rigid/compliant system. The study analyzes how palm movement can enhance grasping performance capabilities. Using data from human hand experiments and finite element analysis (FEA) simulations, the studies predict how palm folding and bulging affect grasping force distribution. This improved modeling allows for more effective robotic design by utilizing palm functions to achieve a broader force distribution in power grasps. A CAPM prototype, integrated into a robotic hand testbed, has been developed to validate the concept and evaluate its effectiveness in grasping by maintaining a stable grasp of a spherical object under an increasing torsional load.