Kinematic Analysis of the Human Thumb with Foldable Palm

Humans demonstrate remarkable capabilities to use a variety of grasp strategies for a given object depending on the context of the task often referred to as grasp affordances in dexterous hands. The interplay among the nervous system, the morphology of the human hand, and the properties of the object to demonstrate these advanced grasp affordance skills are not well understood yet. A key hypothesis addressed in this paper is that the kinematics of the human thumb together with the foldable palm offer a wide variety of choices for the nervous system to plan grasp affordances. This paper provides a new kinematic model to abstract the complex musculoskeletal arrangement of the human thumb, so that its key morphological contributions to wider grasp affordances can be better understood. It also allows to simplify the grasp affordance control strategies. The model was validated using human grasp data base consisting of demonstrations for sixteen grasp types across five human subjects.