SurfMyoAiR: A Surface Electromyography-Based Framework for Airwriting Recognition

Airwriting recognition is the task of identifying letters written in free space with finger movement. It is a dynamic gesture recognition with the vocabulary of gestures corresponding to letters in a given language. Electromyography (EMG) is a technique used to record electrical activity during muscle contraction and relaxation as a result of movement and is widely used for gesture recognition. Most of the current research in gesture recognition is focused on identifying static gestures. However, dynamic gestures are natural and user-friendly for being used as alternate input methods in human–computer interaction (HCI) applications. Airwriting recognition using EMG signals recorded from forearm muscles is, therefore, a viable solution. Since the user does not need to learn any new gestures and a large range of words can be formed by concatenating these letters, it is generalizable to a wider population. There has been limited work in recognition of airwriting using EMG signals and forms the core idea of the current work. The SurfMyoAiR dataset comprising of EMG signals recorded during writing English uppercase alphabets is constructed. Several different time-domain features to construct EMG envelope and two different time–frequency image representations: short-time Fourier transform and continuous wavelet transform were explored to form the input to a deep learning model for airwriting recognition. Several different deep learning architectures were exploited for this task. In addition, the effect of various parameters, such as signal length, window length, and interpolation techniques on the recognition performance, is comprehensively explored. The best-achieved accuracy was 78.50% and 62.19% in user-dependent and user-independent scenarios, respectively, by using short-time Fourier transform in conjunction with a 2-D convolutional neural network (CNN)-based classifier. Airwriting has great potential as a user-friendly modality to be used as an alternate input method in HCI applications.