A Soft Five-Fingered Hand Actuated by Shape Memory Alloy Wires: Design, Manufacturing, and Evaluation

Abstract

This work presents a novel five-fingered soft hand prototype actuated by Shape Memory Alloy (SMA) wires. The use of thin (100 μm diameter) SMA wire actuators, in conjunction with an entirely 3D printed hand skeleton, guarantees an overall lightweight and flexible structure capable of silent motion. To enable high forces with sufficiently high actuation speed at each fingertip, bundles of welded actuated SMA wires are used. In order to increase the compliance of each finger, flexible joints from superelastic SMA wires are inserted between each phalanx. The resulting system is a versatile hand prototype having intrinsically elastic fingers, which is capable to grasp several types of objects with a considerable force. The paper starts with the description of the finger hand design, along with practical considerations for the optimal placement of the superelastic SMA in the soft joint. The maximum achievable displacement of each finger phalanx is measured together with the phalanxes dynamic responsiveness at different power stimuli. Several force measurement are also realized at each finger phalanx. The versatility of the prototype is finally demonstrated by presenting several possible hand configurations while handling objects with different sizes and shapes.

High‐Speed Antagonistic Shape Memory Actuator for High Ambient Temperatures

“…This SMA actuator concept is, therefore, different from a standard antagonistic SMA system, in which two wires are working directly against each other. [32][33][34][35][36] An example of an injection molding process with a built-in valve is shown in Figure 5, explaining the patented operating principle in a more detailed way. [37] On the left-hand side, a simplified injection mold cavity with a drilled valve seat is shown.…”

“…This SMA actuator concept is, therefore, different from a standard antagonistic SMA system, in which two wires are working directly against each other. [ 32–36 ]…”

MHM bracket design on the path of Dr Andrews of true straight wire technique, prototype study design

“…The surface was laser polished to allow for the least possibility for binding or friction with the used wires [ Figure 1 ]. [ 6 7 ] The sliding door has an eyelet on top to facilitate opening and closure by dental explorer [ Figure 2 ].…”

A Soft 3D-Printed Robotic Hand Actuated by Coiled SMA

“…Relevant information is provided in refs. [38][39][40][41][42][43][44][45][46] for a robotic hand or finger design, but one of the first usage of coiled shape memory alloy (SMA) muscles in a robotic finger via antagonistic pairs occurred in an earlier work in 1989. Bergamasco et al demonstrated coiled SMA muscles (0.45 mm wire diameter, 1.5 mm spring diameter, 14 coils and length of 6.3 mm) capable of lifting 3.5 N load a height of 10 mm at 0.11 Hz [45].…”