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Human activity recognition is important for many applications. This paper describes a human activity recognition framework based on feature selection techniques. The objective is to identify the most important features to recognize human activities. We first design a set of new features (called physical features) based on the physical parameters of human motion to augment the commonly used statistical features. To systematically analyze the impact of the physical features on the performance of the recognition system, a single-layer feature selection framework is developed. Experimental results indicate that physical features are always among the top features selected by different feature selection methods and the recognition accuracy is generally improved to 90%, or 8% better than when only statistical features are used. Moreover, we show that the performance is further improved by 3.8% by extending the single-layer framework to a multi-layer framework which takes advantage of the inherent structure of human activities and performs feature selection and classification in a hierarchical manner.

The use of Virtual Reality technology for developing tools for rehabilitation has attracted significant interest in the physical therapy arena. This paper presents a comparison of motion tracking performance between the low-cost Microsoft Kinect and the high fidelity OptiTrack optical system. Data is collected on six upper limb motor tasks that have been incorporated into a game-based rehabilitation application. The experiment results show that Kinect can achieve competitive motion tracking performance as OptiTrack and provide "pervasive" accessibility that enables patients to take rehabilitation treatment in clinic and home environment.

Human daily activity recognition using mobile personal sensing technology plays a central role in the field of pervasive healthcare. One major challenge lies in the inherent complexity of human body movements and the variety of styles when people perform a certain activity. To tackle this problem, in this paper, we present a novel human activity recognition framework based on recently developed compressed sensing and sparse representation theory using wearable inertial sensors. Our approach represents human activity signals as a sparse linear combination of activity signals from all activity classes in the training set. The class membership of the activity signal is determined by solving a l(1) minimization problem. We experimentally validate the effectiveness of our sparse representation-based approach by recognizing nine most common human daily activities performed by 14 subjects. Our approach achieves a maximum recognition rate of 96.1%, which beats conventional methods based on nearest neighbor, naive Bayes, and support vector machine by as much as 6.7%. Furthermore, we demonstrate that by using random projection, the task of looking for “optimal features” to achieve the best activity recognition performance is less important within our framework.

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A method of computer generating binary holograms based on the decomposition of a complex value into two phase quantities is described. Each Fourier transform cell is divided into subcells, and phase quantities are encoded by the detour phase technique. Noise due to the displacement of the subcells and the phase coding is discussed. Methods of suppressing this noise are also included.

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