Humanoid Robot Hand with SMA Actuators and Servo Motors

This paper describes the design of a child humanoid robot hand with SMA actuators and servo motors. Human hands can grasp and manipulate complicated objects relying on its flexible structure and real-time control. However, it is difficult to replicate an exact human hand using rigid structures because of intricate biomechanical structure. In human hand, one metacarpal and three phalanges make up each finger, except for the thumb which only has two phalanges. Each finger except the thumb is composed of 3 joints: the metacarpophalangeal (MCP), the proximal interphalangeal (PIP) and distal interphalangeal joints (DIP). The DIP and PIP joints are always moving simultaneously, while the MCP joint can move independently. The child-sized robot hand is developed which replicates a seven year-old child’s hand in its fundamental structure. The robot hand has five fingers and all the fingers consist of 3 links. Servo motors and shape memory alloy actuators were used as a drive mechanism for the fingers and mathematical model of the SMA actuators are described to study the finger dynamics. A prototype humanoid robot hand was fabricated using 3D printing techniques and experimental results are presented.