Explainable robotic systems: Interpreting outcome-focused actions in a reinforcement learning scenario
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Robotic systems are more present in our society every day. In human-robot interaction scenarios, it is crucial that end-users develop trust in their robotic team-partners, in order to collaboratively complete a task. To increase trust, users demand more understanding about the decisions by the robot in particular situations. Recently, explainable robotic systems have emerged as an alternative focused not only on completing a task satisfactorily but also in justifying, in a human-like manner, the reasons that lead to making a decision. In reinforcement learning scenarios, a great effort has been focused on providing explanations from the visual input modality, particularly using deep learning-based approaches. In this work, we focus on the decision-making process of a reinforcement learning agent performing a navigation task in a robotic scenario. As a way to explain the robot's behavior, we use the probability of success computed by three different proposed approaches: memory-based, learning-based, and phenomenological-based. The difference between these approaches is the additional memory required to compute or estimate the probability of success as well as the kind of reinforcement learning representation where they could be used. In this regard, we use the memory-based approach as a baseline since it is obtained directly from the agent's observations. When comparing the learning-based and the phenomenological-based approaches to this baseline, both are found to be suitable alternatives to compute the probability of success, obtaining high levels of similarity when compared using both the Pearson's correlation and the mean squared error.
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