A hierarchical maze navigation algorithm with Reinforcement Learning and mapping

Goal-finding in an unknown maze is a challenging problem for a Reinforcement Learning agent, because the corresponding state space can be large if not intractable, and the agent does not usually have a model of the environment. Hierarchical Reinforcement Learning has been shown in the past to improve tractability and learning time of complex problems, as well as facilitate learning a coherent transition model for the environment. Nonetheless, considerable time is still needed to learn the transition model, so that initially the agent can perform poorly by getting trapped into dead ends and colliding with obstacles. This paper proposes a strategy for maze exploration that, by means of sequential tasking and off-line training on an abstract environment, provides the agent with a minimal level of performance from the very beginning of exploration. In particular, this approach allows to prevent collisions with obstacles, thus enforcing a safety restraint on the agent.