A two-way flexural rotation manipulator using opposing shape memory alloy wires

This paper presents the design, fabrication, and control of a two-way rotational manipulator using opposing shape memory alloy (SMA) wire actuated flexures. Monolithic flexure mechanisms have no friction/backlash and are capable of miniaturization. SMA exhibits large stroke, high energy density, and requires low driving voltage. Combining SMA as driver and flexure as force/motion transmitter makes them 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 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. By parallel connecting two flexure mechanisms with two opposing one-way SMA wires, the manipulator achieves two-way motion without sacrificing stroke. By actively contracting and extending, two-way manipulators are much faster than owe-way manipulators that rely passively on bias spring to extend. A feedback PID control algorithm with fuzzy-tuning gains is implemented to precisely control the response of the manipulator. We illustrate the two-way performance by several tracking response experiments. With the merits shown, we expect this type of manipulator can be utilized in meso to micro scale applications.