Design of a humanoid hand using segmented shape memory alloy actuators

Abstract

Despite amazing progress in the past two decades, the field of robotics has yet to produce a robotic hand with the same dexterity as the human hand. There has yet to even be a functioning robotic hand of the same size and weight as the human hand. These deficiencies can be attributed to the size, weight and complexity of the actuators used in these robotic hands. Thermal shape memory alloys (SMA's) have characteristics such as high power density which indicate that they would be ideal actuators for such applications. However, certain characteristics of SMA exist which, if left unaddressed, make usage as an actuator impractical. The implementation of SMA for the actuation of a 20 degree of freedom robotic hand and forearm is investigated. A segmented actuation design for the SMA is implemented to address issues of practicality; other issues with regards to the controllability, response time and limited strain of the SMA are addressed. A 20 degree of freedom robotic hand with 16 controlled axes is designed along with a 32 axis actuator box. The designs are realized and the result is a functioning robotic hand of similar size and weight to the human hand. It is concluded that thermal shape memory alloys are a viable solution for the purposes of compact lightweight actuation of vast degree of freedom systems.