Development of a Measuring System of Contact Force for Braille Reading Using a Six-Axis Force Sensor

Abstract

The objective of the recent research effort on tactile sensation is to provide the blind or visually impaired (BVI) persons with a more natural handling of their surrounding environment. To generate natural fingertip stimulations, the forces felt by the fingertip should be characterized. This work presents an approach to measure the fingertip forces while reading Braille characters. In the proposed experimental procedure, a subject is asked to identify five individual Braille characters that are hidden from view. Each Braille character is mounted on top of a six–axis force sensor. The experiment requires that each subject places a fingertip normal to a Braille character until the character is identified. The same experiment is repeated but with the subject applying pressure in the tangential direction. A new approach is proposed to identify these forces to ensure the validity of the readings. The subject is then asked to identify the letter out of images of the Braille characters. Twenty-eight subjects participated in the experiment so far. Data are statistically analyzed to obtain a general form of force-time history during the phase of Braille character identification. Normalization of the data is explored by identifying the equivalent fingertip pressure.