PEAR: Primitive enabled Adaptive Relabeling for boosting Hierarchical Reinforcement Learning
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Hierarchical reinforcement learning (HRL) has the potential to solve complex long horizon tasks using temporal abstraction and increased exploration. However, hierarchical agents are difficult to train as they suffer from inherent non-stationarity due to continuously changing low level primitive. We present primitive enabled adaptive relabeling (PEAR), a two-phase approach where firstly we perform adaptive relabeling on a few expert demonstrations to generate subgoal supervision dataset, and then employ imitation learning for regularizing HRL agents. We bound the sub-optimality of our method using theoretical bounds and devise a practical HRL algorithm for solving complex robotic tasks. We perform experiments on challenging robotic tasks: maze navigation, pick and place, rope manipulation and kitchen environments, and demonstrate that the proposed approach is able to solve complex tasks that require long term decision making. Since our method uses a handful of expert demonstrations and makes minimal limiting assumptions on task structure, it can be easily integrated with typical model free reinforcement learning algorithms to solve most robotic tasks. We empirically show that our approach outperforms previous hierarchical and non-hierarchical baselines, and exhibits better sample efficiency. We also perform real world robotic experiments by deploying the learned policy on a real robotic rope manipulation task and demonstrate that PEAR consistently outperforms the baselines. Here is the link for supplementary video: <https://tinyurl.com/pearOverview>
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