A compact rotational manipulator using shape memory alloy wire actuated flexures

This paper presents the design, fabrication, and control of a rotational manipulator using shape memory alloy (SMA) wire actuated flexures. Monolithic flexure mechanisms have no friction/backlash and are capable of miniaturization. They are well-suited for tasks that required high precision and packed space. To explore flexure shapes beyond traditional notch hinges and leaf springs, we present a general two-step design method to find the optimal flexure shapes for maximal rotation without yield. The advantages gained from shape variations are shown through a simulation example. We further use a SMA wire to drive the flexure. SMA exhibits large stroke with high power density and requires low driving voltage. By using versatile SMA wire, the rotational range of the manipulator can be significantly increased while the overall size can be kept compact. A feedback PID control algorithm with fuzzy-tuned gains is implemented to precisely control the response of the manipulator. We illustrate its performance by tracking and step response experiments. With the merits shown, we expect this type of manipulator can be utilized in meso to micro scale applications.