Braille recognizing methods of tactile sensor. (a) Schematic illustration of the Braille learning is crucial for the VI reading, learning and communicating with the world. (b) Photograph of the tailored Braille board for learning Braille by the developed sensors. (c) Digital photo showing a Braille board with twenty-six English letters and relative resistance change response curves when sliding the sensor unit across the Braille board one by one through the 2B-sensor. (d) Evaluation results of Braille recognition based on six kinds of machine learning methods. (e) Processing methods of machine learning. (f) Confusion matrix of twenty-six letters with a two-channel 2B-sensor.