A hierarchical method for human concurrent activity recognition using miniature inertial sensors

Purpose - Existing studies on human activity recognition using inertial sensors mainly discuss single activities. However, human activities are rather concurrent. A person could be walking while brushing their teeth or lying while making a call. The purpose of this paper is to explore an effective way to recognize concurrent activities. Design/methodology/approach - Concurrent activities usually involve behaviors from different parts of the body, which are mainly dominated by the lower limbs and upper body. For this reason, a hierarchical method based on artificial neural networks (ANNs) is proposed to classify them. At the lower level, the state of the lower limbs to which a concurrent activity belongs is firstly recognized by means of one ANN using simple features. Then, the upper- level systems further distinguish between the upper limb movements and infer specific concurrent activity using features processed by the principle component analysis. Findings - An experiment is conducted to collect realistic data from five sensor nodes placed on subjects' wrist, arm, thigh, ankle and chest. Experimental results indicate that the proposed hierarchical method can distinguish between 14 concurrent activities with a high classification rate of 92.6 per cent, which significantly outperforms the single- level recognition method. Practical implications - In the future, the research may play an important role in many ways such as daily behavior monitoring, smart assisted living, postoperative rehabilitation and eldercare support. Originality/value - To provide more accurate information on people's behaviors, human concurrent activities are discussed and effectively recognized by using a hierarchical method.