Design of a mini-braille cell using SMA-based actuators

• Main Author: Cortez, John Vincent P.
• Format: text
• Language: English
• Published: Animo Repository 2023
• Subjects: Braille; Engineering; Other Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etdm_mem/10; https://animorepository.dlsu.edu.ph/context/etdm_mem/article/1011/viewcontent/CORTEZ_THESIS_MANUSCRIPT_SIGNED_COMPLETE.pdf
• Institution: De La Salle University

Over 39 million people are afflicted with blindness in the world today. The Braille code is the alphabet used for the education and activities of daily life (ADL) of the blind and visually impaired (BVI). Refreshable braille displays (RBD) are electronic devices capable of outputting braille characters. However, these displays are still much larger compared to typical electronic displays. While voice inputs and outputs can be used by the BVI, a codified language still has its own advantages for specific ADL. With the advent of wearable devices in the past years, RBDs that can be integrated into such can open the technology to BVIs and present new market opportunities. This study presents a novel design for a mini-braille cell using actuators made from shape memory alloys (SMA). The housing is designed using CAD software and printed in a DLP 3D printer. The SMA-actuators were created from SMA wires that were programmed using a bending method that was developed and honed for this study. An Arduino microcontroller was used to operate the prototype. A PWM control scheme was implemented to regulate the heat required by the SMA-actuator. The resulting mini-braille cell was tested and compared with a commercially available RBD, the Metec P20 braille cell. The final prototype, though built at 150% scale of the original design, is still smaller by 59.5% in volume and lighter by 25% with the final dimensions of 25.5mm by 9.2mm by 8.1mm and a weight of 3g. The output force of the raised braille dots was greater by 300%, lifting at least 75g of load. However, while the actuation force was improved, the refresh rate is slower. The prototype was demonstrated to be capable of displaying different braille characters. However, heat bleeds from activated braille dots to inactivated ones, resulting in errors in the character display. 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 values used for the control scheme could also improve the functionality of the mini-braille cell.