An Extensor Mechanism for an Anatomical Robotic Hand

The human finger possesses a structure called the extensor mechanism, a web-like collection of tendinous material that lies on the dorsal side of each finger and connects the controlling muscles to the bones of the finger. In past robotic hand designs, extensor mechanisms have generally not been employed due in part to their complexity and a lack of understanding of their utility. This paper presents our first design and analysis effort of an artificial extensor mechanism. The goal of our analysis is to provide an understanding of the extensor mechanism’s functionality so that we can extract the crucial features that need to be mimicked to construct an anatomical robotic hand. With the inclusion of an extensor mechanism, we believe all possible human finger postures can be achieved using four cable driven actuators. We identified that this extensor mechanism gives independent control of the metacarpo-phalangeal (MCP) joint and acts not only as an extensor but also as a flexor, abductor, adductor, or rotator depending on the finger’s posture.