Tongue interface based on surface EMG signals of suprahyoid muscles

Makoto Sasaki,Masahiro Yoshikawa,Atsushi Nakayama,Goro Obinata,Dimitar Stefanov,Katsuhiro Kamata,Kohei Onishi

doi:10.1186/s40648-016-0048-0

Makoto Sasaki, Masahiro Yoshikawa + Show 5 more

Open Access

https://doi.org/10.1186/s40648-016-0048-0

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Abstract

The research described herein was undertaken to develop and test a novel tongue interface based on classification of tongue motions from the surface electromyography (EMG) signals of the suprahyoid muscles detected at the underside of the jaw. The EMG signals are measured via 22 active surface electrodes mounted onto a special flexible boomerang-shaped base. Because of the sensor’s shape and flexibility, it can adapt to the underjaw skin contour. Tongue motion classification was achieved using a support vector machine (SVM) algorithm for pattern recognition where the root mean square (RMS) features and cepstrum coefficients (CC) features of the EMG signals were analyzed. The effectiveness of the approach was verified with a test for the classification of six tongue motions conducted with a group of five healthy adult volunteer subjects who had normal motor tongue functions. Results showed that the system classified all six tongue motions with high accuracy of 95.1 ± 1.9 %. The proposed method for control of assistive devices was evaluated using a test in which a computer simulation model of an electric wheelchair was controlled using six tongue motions. This interface system, which weighs only 13.6 g and which has a simple appearance, requires no installation of any sensor into the mouth cavity. Therefore, it does not hinder user activities such as swallowing, chewing, or talking. The number of tongue motions is sufficient for the control of most assistive devices.

Highlights

A tongue is an intra-oral locomotorium that can be moved quickly and precisely according to one’s own will
This paper proposes a novel tongue interface based on classification of the tongue motions from surface EMG signals of the suprahyoid muscles detectable at the underside of the jaw
Because the distance of moving backward is about 1 m in daily life, the influence of these errors is believed to present no difficulty. These results suggest that the straight driving performance of an electric wheelchair using the proposed tongue interface is sufficient for practical use

Summary

Introduction

A tongue is an intra-oral locomotorium that can be moved quickly and precisely according to one’s own will. Anyone can set their own tongue position precisely and can smoothly change the magnitude of the force imposed on the teeth or palate. Tongue motor functions are usually preserved even in people with cervical spinal cord damage. An interface system based on a small joystick operated by the tongue has been presented in the literature [3]. The joystick is fixed in a suitable position via a special arm mount.

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