Investigation of a gripping device actuated by SMA wire

A gripping device actuated by shape memory alloy (SMA) wire was fabricated and investigated. The actuation mechanism and the working principle of the gripping device are simple. A SMA wire was used to close the gripper during operation and a torsion spring was integrated to open the gripper when the SMA wire relaxed. Several experiments were conducted to investigate the performance of the gripping device. The aspects investigated include gripping force, response time and cyclic test number of the gripping device. It was found that factors such as driving current, torsion-spring torque, SMA wire diameter and the number of coils the SMA wire was wound had significant effects on the gripping device's performance. The gripping force was adjustable by changing the driving current. The gripping device using one coil of Ø 100 μm SMA wire with a music wire spring produced good performance and the gripping device could withstand over 1.175 million opening and closing cycles without any deterioration in its performance.