Miniature Shape Memory Alloy Actuator for Tactile Binary Information Display

This paper presents a new miniature actuator, which is currently being used to design and develop high resolution, lightweight and compact interfaces for tactile binary information representation such as Braille. Since the main drawback of these devices is their high cost, the proposed actuator exploits the simplicity of its design to provide a low-cost actuation alternative. Based on shape memory alloy (SMA) technology, the actuator consists of an antagonist arranged pair of NiTi helical springs. The actuator of 1.5 mm diameter and 150 mg weight is capable of developing a 320 mN pull force and 1.5 Hz bandwidth by using simple forced-air convection. A combined computational/experimental study on the thermomechanical properties of both SMA active element and actuator is presented to evaluate characteristics such as actuation speed, force and stroke. In conclusion, the prototype and performance results are reported and discussed.