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A closed-loop deep learning architecture for robust activity recognition using wearable sensors

Human activity recognition (HAR) plays a central role in health-care, fitness and sport applications because of its potential to enable context-aware human monitoring. With the increase in popularity of wearable devices, we are witnessing a large influx in availability of human activity data. For effective analysis and interpretation of these heterogeneous and high-volume streaming data, we need powerful algorithms. In particular, there is a strong need for developing algorithms for robust classification of human activity data that specifically address challenges associated with dynamic environments (e.g. different users, signal heterogeneity). We use the term robust here in two, orthogonal senses: 1) leveraging related data in such a way that knowledge is transferred to a new context; and 2) actively reconfiguring machine learning algorithms such that they can be applied in a new context. In this paper, we propose an architecture that combines an active learning approach with a novel deep network. Our deep neural network exploits both Convolutional and Long Short-Term Memory (LSTM) layers in order to learn hierarchical representation of features and capture time dependencies from raw-data. The active learning process allows us to choose the best instances for fine-tuning the deep network to the new setting in which the system operates (i.e. a new subject). We demonstrate the efficacy of the architecture using real data of human activity. We show that the accuracy of activity recognition reaches over 90% by annotating less than 20% of unlabeled data.