High-speed and high-efficiency shape memory alloy actuation

When standard voltage levels commonly adopted in industry are used to activate thermal shape memory alloy (SMA) wire actuators, they often result in very high electrical currents which may eventually damage or destroy the actuators. To improve performance of SMA wire actuators operating in industrial environments, in this paper we investigate a novel, fast and energy-efficient actuation strategy based on short pulses in the millisecond range. The use of higher voltages leads to a highly dynamic activation process, in contrast to commonly used quasi-static activation based on low-voltage. A test setup is designed to examine the effects of the control parameters (i.e., supply voltage, activation pulse duration, SMA wire pre-tension and wire diameter) on the measured displacement and force output of the SMA wire. It is shown that actuation times in the range of 20 ms and strokes of more than 10% of the SMA wire length can be reached. Additionally, energy savings of up to 80% with respect to conventional quasi-static actuation are achieved. Possible applications for this activation method are release mechanisms, switches or safety applications.