Development of an Adaptive Gripper Using Shape Memory Alloys for Industrial Robotics

Abstract

Industrial Robotic Grippers (IRG) with elasticity have significant advantages in grasping items with 
irregular shapes or fragility compared to conventional rigid gripping devices. The primary constraints of these 
systems are the diminished gripping force due to the characteristics of soft motors and the absence of variable 
rigidity in IRG devices, which restricts their applicability across a broader spectrum of uses. This article 
presents a soft gripper using Shape-Memory Alloy (SMA) technology, with three robotic digits that enable 
compliant gripping at moderate stiffness and secure holding with elevated rigidity. Each IRG finger (Fr) 
primarily included rigid components and two variable rigidity joints, affixed to the base at a predetermined 
angle. The paraffin, used as a variable rigidity substance in the joint, is thermally manipulated to alter the 
rigidity of the IRG Frs. Experimental results indicate that a single IRG Fr gets an estimated 18-fold increase in 
stiffness. Every finger, possessing two joints, proactively attains various postures by modulating the stiffness 
of the joints and activating the SMA wire. Utilizing these concepts, the gripper can grasp items of multiple forms 
and a wide range of weights, with the most significant gripping force enhanced to almost tenfold with adjustable 
stiffness connections. The final test is performed to verify the changing stiffness of the suggested soft grippers 
while grabbing an item.