Design of a Mini-Braille Cell Using Shape Memory Alloy-Based Actuators

Refreshable braille displays (RBD) are electronic devices capable of outputting braille characters. However, these are larger compared to typical displays. RBDs that can be integrated into wearable devices or assistive devices can provide the blind and visually impaired (BVI) new alternatives to learn and navigate. This study explores a novel mini-braille cell design utilizing shape memory alloy (SMA) actuators. The SMAactuators were created from SMA wires that were programmed using a unique bending method. Subsequently, a PWM control scheme was utilized to regulate the SMA-actuators’ heat. The prototype was compared against an existing braille cell, the Metec P20 braille cell, wherein our prototype demonstrated almost 60% reduction in volume and is 25% lighter, measuring 25.5mm x 9.2mm x 8.1mm and weighing 3g. The output force of the raised braille dots was greater by 300% that can lift at least 75g of load. However, the refresh rate was slower, and heat transfer between activated and inactivated dots caused character display errors. These issues may be addressed in the future by improving the design and precision of the manufacturing of its components, particularly the SMA-actuators. Fine-tuning the control values could also improve the prototype's functionality. Index Terms—shape memory alloys, refreshable braille display, mini braille cell