The design of a hybrid DC motor/SMA actuated robotic hand based on physiological and anatomical synergies

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 73-74).A new approach to the design and control of multi-fingered hands using hybrid DC motor-Shape Memory Alloy (SMA) array actuators is presented in this thesis. The fundamental design concept is based on the principle of motor control synergy, a biomechanics terminology for coordinated motion generation. Principal component analysis is used for determining the most significant direction as well as the residual directions. A single DC motor is used for driving multiple fingers at a particular velocity distribution over a vast number of finger joints corresponding to the direction of the most significant synergy. SMA array actuators are used for driving the fingers in the residual directions. Although many actuator axes are needed for spanning the residual space, the required strokes are much shorter than the most significant direction; compact and high energy-density SMA actuators meet these requirements. The thesis presents synergistic integration of these two types of actuators having diverse characteristics. This allows us to embed all the actuators and transmission mechanisms in the palm, eliminating a bundle of tendons crossing over the wrist joints. An initial prototype hand is designed and built.by Josiah Benjamin Rosmarin.S.M

Design of a humanoid hand using segmented shape memory alloy actuators

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 48).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.by Josiah Benjamin Rosmarin.S.B