Flexure Hinge-based Biomimetic Thumb with a Rolling-Surface Metacarpal Joint

The human thumb's state contribution to grasping and dexterous manipulation of objects is a function of the kinematic multiplicity of joints and structure of the bones, joints, and ligaments. This paper looks at the design and evaluation of a human-like thumb for use in a robotic hand, where the thumb's state contribution to grasping and dexterous manipulation is a function of a simplified kinematic model based on that of the human thumb, but also on empirical trials of surgical techniques to retain functionality while reducing the number of joints in the thumb. Motion Capture Data of the End Effector is analyzed with the measured excursion of the tendons to determine the relationship between tendon velocities and task-space velocities. After validating the procedure experimentally, a simplified metric is proposed to represent this data, and shows that our prototype is predicted to have a relatively smooth mapping between tendon excursion velocity and end effector velocity.