Air-Writing Character Recognition with Ultrasonic Transceivers

• Published in: Sensors (Basel, Switzerland) Switzerland), 2021-10, Vol.21 (20), p.6700
• Main Authors: Saez-Mingorance, Borja, Mendez-Gomez, Javier, Mauro, Gianfranco, Castillo-Morales, Encarnacion, Pegalajar-Cuellar, Manuel, Morales-Santos, Diego P.
• Format: Article
• Language: English
• Subjects: air-writing; Algorithms; Character recognition; deep learning; gesture recognition; Neural networks; Noise; Receivers & amplifiers; Sensors; Transceivers; Ultrasonic imaging; ultrasound; Writing
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s21206700

The interfaces between users and systems are evolving into a more natural communication, including user gestures as part of the interaction, where air-writing is an emerging application for this purpose. The aim of this work is to propose a new air-writing system based on only one array of ultrasonic transceivers. This track will be obtained based on the pairwise distance of the hand marker with each transceiver. After acquiring the track, different deep learning algorithms, such as long short-term memory (LSTM), convolutional neural networks (CNN), convolutional autoencoder (ConvAutoencoder), and convolutional LSTM have been evaluated for character recognition. It has been shown how these algorithms provide high accuracy, where the best result is extracted from the ConvLSTM, with 99.51% accuracy and 71.01 milliseconds of latency. Real data were used in this work to evaluate the proposed system in a real scenario to demonstrate its high performance regarding data acquisition and classification.