15,484 research outputs found
MP3: Movement Primitive-Based (Re-)Planning Policy
We introduce a novel deep reinforcement learning (RL) approach called
Movement Prmitive-based Planning Policy (MP3). By integrating movement
primitives (MPs) into the deep RL framework, MP3 enables the generation of
smooth trajectories throughout the whole learning process while effectively
learning from sparse and non-Markovian rewards. Additionally, MP3 maintains the
capability to adapt to changes in the environment during execution. Although
many early successes in robot RL have been achieved by combining RL with MPs,
these approaches are often limited to learning single stroke-based motions,
lacking the ability to adapt to task variations or adjust motions during
execution. Building upon our previous work, which introduced an episode-based
RL method for the non-linear adaptation of MP parameters to different task
variations, this paper extends the approach to incorporating replanning
strategies. This allows adaptation of the MP parameters throughout motion
execution, addressing the lack of online motion adaptation in stochastic
domains requiring feedback. We compared our approach against state-of-the-art
deep RL and RL with MPs methods. The results demonstrated improved performance
in sophisticated, sparse reward settings and in domains requiring replanning.Comment: The video demonstration can be accessed at
https://intuitive-robots.github.io/mp3_website/. arXiv admin note: text
overlap with arXiv:2210.0962
Metareasoning for Planning Under Uncertainty
The conventional model for online planning under uncertainty assumes that an
agent can stop and plan without incurring costs for the time spent planning.
However, planning time is not free in most real-world settings. For example, an
autonomous drone is subject to nature's forces, like gravity, even while it
thinks, and must either pay a price for counteracting these forces to stay in
place, or grapple with the state change caused by acquiescing to them. Policy
optimization in these settings requires metareasoning---a process that trades
off the cost of planning and the potential policy improvement that can be
achieved. We formalize and analyze the metareasoning problem for Markov
Decision Processes (MDPs). Our work subsumes previously studied special cases
of metareasoning and shows that in the general case, metareasoning is at most
polynomially harder than solving MDPs with any given algorithm that disregards
the cost of thinking. For reasons we discuss, optimal general metareasoning
turns out to be impractical, motivating approximations. We present approximate
metareasoning procedures which rely on special properties of the BRTDP planning
algorithm and explore the effectiveness of our methods on a variety of
problems.Comment: Extended version of IJCAI 2015 pape
Crossmodal content binding in information-processing architectures
Operating in a physical context, an intelligent robot faces two fundamental problems. First, it needs to combine information from its different sensors to form a representation of the environment that is more complete than any of its sensors on its own could provide. Second, it needs to combine high-level representations (such as those for planning and dialogue) with its sensory information, to ensure that the interpretations of these symbolic representations are grounded in the situated context. Previous approaches to this problem have used techniques such as (low-level) information fusion, ontological reasoning, and (high-level) concept learning. This paper presents a framework in which these, and other approaches, can be combined to form a shared representation of the current state of the robot in relation to its environment and other agents. Preliminary results from an implemented system are presented to illustrate how the framework supports behaviours commonly required of an intelligent robot
TreeQN and ATreeC: Differentiable Tree-Structured Models for Deep Reinforcement Learning
Combining deep model-free reinforcement learning with on-line planning is a
promising approach to building on the successes of deep RL. On-line planning
with look-ahead trees has proven successful in environments where transition
models are known a priori. However, in complex environments where transition
models need to be learned from data, the deficiencies of learned models have
limited their utility for planning. To address these challenges, we propose
TreeQN, a differentiable, recursive, tree-structured model that serves as a
drop-in replacement for any value function network in deep RL with discrete
actions. TreeQN dynamically constructs a tree by recursively applying a
transition model in a learned abstract state space and then aggregating
predicted rewards and state-values using a tree backup to estimate Q-values. We
also propose ATreeC, an actor-critic variant that augments TreeQN with a
softmax layer to form a stochastic policy network. Both approaches are trained
end-to-end, such that the learned model is optimised for its actual use in the
tree. We show that TreeQN and ATreeC outperform n-step DQN and A2C on a
box-pushing task, as well as n-step DQN and value prediction networks (Oh et
al. 2017) on multiple Atari games. Furthermore, we present ablation studies
that demonstrate the effect of different auxiliary losses on learning
transition models
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