A Novel Braille Display Using the Vibration of SMA Wires and the Evaluation of Braille Presentations

In this study, a new Braille display is constructed based on the vibration of a Shape Memory Alloy (SMA) wire. To present Braille information, a vibration actuator is used instead of conventional Braille dots. According to the temperature-dependent characteristic shrinkage and the vest ration to the initial length of an SMA wire, a vibration actuator which can be driven by several Hz-100 Hz pulse signals has been developed. A method for presenting Braille information is proposed by the application of the developed actuator to a Braille display. In this research, multiple actuators constructed by using metal pins (0.7 mm in diameter, 3 mm in length) and SMA wires (50 um in diameter, 3 mm in length), are placed as to form standard Braille. The actuators are vibrated by PWM signals with different frequencies and appropriate timings, and the effectiveness of the proposed method for Braille display is verified by experiments. From the experimental results, the highest recognition rate of 100 % was achieved under the conditions of 50 Hz vibration frequency and 500 ms time delay. This means the vibration patterns effectively stimulated the Meissner corpuscles, and helped the subjects properly discriminate Braille characters presented by the developed display. Good evaluations were received from the subjects who are visually-impaired.