Optimal design of rotary manipulators using shape memory alloy wire actuated flexures

This paper presents the design and implementation of rotary manipulators using shape memory alloy (SMA) wire actuated flexures. Monolithic flexures transmit motion and force without 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 load transmitter makes them well-suited for tasks that required high precision and compact space. To explore flexure shapes beyond traditional notch hinges and leaf springs, we present a general optimization method to find the optimal shapes for maximal rotation without yield. The advantages gained from shape variations are shown through several simulations. One-way and two-way manipulators are both validated. By parallel connecting two one-way manipulators with two opposing SMA wires, we contribute a new two-way manipulator to achieve bi-directional motion without sacrificing SMA strain. The two-way manipulator actively contracts and extends. Therefore it is much faster than owe-way manipulators the extension of which relies passively on flexural force. A feedback PID controller with fuzzy-tuned gains is implemented to precisely control the motion of the manipulators. We illustrate their performance by step and tracking response experiments. With the merits shown, we expect this type of manipulator can be utilized in meso to micro scale applications.