# Design and Implementation of a Semantic Information Expression Device Based on Vibrotactile Coding
## 1 Introduction  
In daily life, in addition to sight and hearing, haptic is an important information acquisition channel for human beings [1]. When sight and hearing are limited in conditions such as in dark or noisy environments, relying on the tactile sense to acquire or convey information becomes extremely efficient [2; 3; 4]. Braille, as one of the most common forms of tactile communication used by people with hearing and sight impairments, is also the basis for their use of tactile expression [5; 6; 7]. Vibrotactile technology is the most widely used technology in the field of haptic expression [8; 9]. A haptic expression device about information is a tactile stimulus that is applied to the human skin in order to feedback specific information to the user. Vibrotactile technology uses vibratory stimuli, such as mechanical vibrations generated by micromotors, solenoids, voice coils, piezoelectric crystals, etc. [10], which are delivered to the surface of the user's skin at a low frequency, and the user perceives and interprets the information expressed by the vibratory stimuli. In order to perform vibrotactile expression of Braille information, domestic and foreign researchers have developed various tactile expression devices [11; 12], which are briefly categorized here as the direct-contact and body-worn types. Body-worn devices belong to the \"Body-Braille\" system [13; 14], which can be placed on the surface of any part of the body, and the user is able to passively access Braille information. This means that the user can keep their hands free while understanding the Braille information, even if the device is a glove, and performing other things with their hands does not affect the acquisitionof Braille information. Direct-contact devices, on the other hand, use fingers to touch the surface of the device directly to obtain Braille information. It does not allow keeping the hands free like a body-worn device, but it is more suitable for Braille reading. Since paper Braille is initially read with the finger, it is easier and quicker for the user to learn how to use the device. Most of the body-worn devices for semantic information acquisition are gloves and wristbands. In 2017, [PERSON] designed a BrailleBand [15], in which six motors in three bands correspond to a Braille cell to read the Braille information with its vibration. However, its reading speed and reading accuracy are related to the character gap, and the accuracy increases but the reading speed decreases when the character gap increases. In the same year, based on finger Braille (the index, middle, and ring fingers of both hands correspond to the six dots of the Braille characters, and the vibrating device is set on these six fingers), [PERSON] designed a glove for Braille communication [16], where the Braille information is delivered to the glove, the corresponding finger vibrates, and the subject interprets the information and inputs it into a cell phone program. However, the experiment only tested whether the device could correctly transmit and express Braille information, and the results showed that the correct transmission could be carried out. Based on this and a variety of assistive technologies, in 2020, [PERSON] upgraded the device with integrated sensors and actuators [17]. Non-blind subjects were tested to be able to read two types of Braille words with 68% and 75% accuracy. As for direct-contact devices, the earliest vibrotactile expression device appeared in 1970, Braille printers for the blind designed by [PERSON] et al. [18], which was the first device used to help blind people with text reading. The device enlarged and imaged letters on an array, and controlling the vibration of motors in the array resulted in a vibrating tactile image that the user could touch-read, but the range of readability was only 92-98%. Since then, because of the emergence of touchscreen phones, designing vibrotactile interactions based on the phone has become a very common means [19; 20; 21].