Assistive robots in ambient assisted living environments can be equipped with learning capabilities to effectively learn and execute human activities. This paper proposes a human activity learning (HAL) system for application in assistive robotics. An RGB-depth sensor is used to acquire information of human activities, and a set of statistical, spatial and temporal features for encoding key aspects of human activities are extracted from the acquired information of human activities. Redundant features are removed and the relevant features used in the HAL model. An ensemble of three individual classifiers-support vector machines (SVMs), K -nearest neighbour and random forest-is employed to learn the activities. The performance of the proposed system is improved when compared with the performance of other methods using a single classifier. This approach is evaluated on experimental dataset created for this work and also on a benchmark dataset-the Cornell Activity Dataset (CAD-60). Experimental results show the overall performance achieved by the proposed system is comparable to the state of the art and has the potential to benefit applications in assistive robots for reducing the time spent in learning activities.

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Human activity recognition (HAR) and transfer learning (TL) are two broad areas widely studied in computational intelligence (CI) and artificial intelligence (AI) applications. Much effort has been put into developing suitable solutions to advance the current performance of existing systems. However, challenges are facing the existing methods of HAR. In HAR, the variations in data required in HAR systems pose challenges to many existing solutions. The type of sensory information used could play an important role in overcoming some of these challenges. Vision-based information in 3D acquired using RGB-D cameras is one type. Furthermore, with the successes encountered in TL, HAR stands to benefit from TL to address challenges to existing methods. Therefore, it is important to review the current state-of-the-art related to both areas. This paper presents a comprehensive survey of vision-based HAR using different methods with a focus on the incorporation of TL in HAR methods. It also discusses the limitations, challenges and possible future directions for more research.

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Transfer Learning (TL) aims to learn a problem from a source reference to improve on the performance achieved in a target reference. Recently, this concept has been applied in different domains, especially, when the data in the target is insufficient. TL can be applied across domains or across tasks. However, the challenges related to what to transfer, how to transfer and when to transfer create limitations in the realisation of this concept in day to day applications. To address the challenges, this paper presents an overview of the concept of TL and how it can be applied in human-robot interaction for assistive robots requiring to learn human tasks in Ambient Assisted Living environments. The differences in feature spaces between a human (source domain) and robot (target domain) makes it difficult for tasks to be directly learned by robots. To address the challenges of this task, we propose a model for learning across feature spaces by mapping the features in the source domain to the target domain features.