Modeling manipulation interactions by hidden Markov models

This paper describes a new approach on how to teach everyday manipulation tasks to a robot under the "Learning from Observation" framework. In our previous work, to acquire low-level action primitives of a task automatically, we proposed a technique to estimate essential interactions to complete a task by integrating multiple observations of similar demonstrations. But after many demonstrations are performed, there may be interactions which are the same in nature. These identical interactions should be grouped so that each action primitive becomes unique. For this purpose, a Hidden Markov Model based clustering algorithm is presented which automatically determines the number of independent interactions. We also show that the obtained interactions can be used as discriminators of human behavior. Finally, simulation and experimental results in which a real humanoid robot learns and recognizes essential actions by observing demonstrations are presented.