Investigation to the Influence on Energy Conversion Efficiency for Shape Memory Alloy Coil with Pulse Width Modulated Control

In this article, we analyze the frequency displacement response and the energy conversion efficiency of shape memory alloy (SMA) coil under the controls of square wave and pulse width modulated (PWM) wave. In our experiment, the frequency displacement response of SMA coil with the changing of signal frequency and duty cycle was observed by the 3D optical location tracking system (NDI Polaris) with a sampling frequency of 10 Hz. The experimental results reveal less temperature difference can decrease the necessary heat for phase transformation of materials and the SMA actuator controlled by PWM wave can effectively improve the energy conversion efficiency through reducing the heat release. To minimize the energy consumption, a control strategy of pulse width modulated (PWM) wave with less working duty cycle, less pulse duty cycle and greater electric current under appropriate temperature are proposed.