A Finite Horizon DEC-POMDP Approach to Multi-robot Task Learning (original) (raw)
Related papers
2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2017
This paper presents a data-driven approach for multi-robot coordination in partially-observable domains based on Decentralized Partially Observable Markov Decision Processes (Dec-POMDPs) and macro-actions (MAs). Dec-POMDPs provide a general framework for cooperative sequential decision making under uncertainty and MAs allow temporally extended and asynchronous action execution. To date, most methods assume the underlying Dec-POMDP model is known a priori or a full simulator is available during planning time. Previous methods which aim to address these issues suffer from local optimality and sensitivity to initial conditions. Additionally, few hardware demonstrations involving a large team of heterogeneous robots and with long planning horizons exist. This work addresses these gaps by proposing an iterative sampling based Expectation-Maximization algorithm (iSEM) to learn polices using only trajectory data containing observations, MAs, and rewards. Our experiments show the algorithm is able to achieve better solution quality than the state-of-the-art learning-based methods. We implement two variants of multi-robot Search and Rescue (SAR) domains (with and without obstacles) on hardware to demonstrate the learned policies can effectively control a team of distributed robots to cooperate in a partially observable stochastic environment.
2016
Decentralized partially observable Markov decision processes (Dec-POMDPs) provide a general framework for multiagent sequential decision-making under uncertainty. Although Dec-POMDPs are typically intractable to solve for real-world problems, recent research on macro-actions (i.e., temporally-extended actions) has significantly increased the size of problems that can be solved. However, current methods assume the underlying Dec-POMDP model is known a priori or a full simulator is available during planning time. To accommodate more realistic scenarios, when such information is not available, this paper presents a policy-based reinforcement learning approach, which learns the agent policies based solely on trajectories generated by previous interaction with the environment (e.g., demonstrations). We show that our approach is able to generate valid macro-action controllers and develop an expectation-maximization (EM) algorithm (called Policy-based EM or PoEM), which has convergence gua...
The International Journal of Robotics Research, 2017
This work focuses on solving general multi-robot planning problems in continuous spaces with partial observability given a high-level domain description. Decentralized Partially Observable Markov Decision Processes (Dec-POMDPs) are general models for multi-robot coordination problems. However, representing and solving Dec-POMDPs is often intractable for large problems. This work extends the Dec-POMDP model to the Decentralized Partially Observable Semi-Markov Decision Process (Dec-POSMDP) to take advantage of the high-level representations that are natural for multi-robot problems and to facilitate scalable solutions to large discrete and continuous problems. The Dec-POSMDP formulation uses task macro-actions created from lower-level local actions that allow for asynchronous decision-making by the robots, which is crucial in multi-robot domains. This transformation from Dec-POMDPs to Dec-POSMDPs with a finite set of automatically-generated macro-actions allows use of efficient discr...
Scalable Planning and Learning for Multiagent POMDPs: Extended Version
arXiv: Artificial Intelligence, 2014
Online, sample-based planning algorithms for POMDPs have shown great promise in scaling to problems with large state spaces, but they become intractable for large action and observation spaces. This is particularly problematic in multiagent POMDPs where the action and observation space grows exponentially with the number of agents. To combat this intractability, we propose a novel scalable approach based on sample-based planning and factored value functions that exploits structure present in many multiagent settings. This approach applies not only in the planning case, but also the Bayesian reinforcement learning setting. Experimental results show that we are able to provide high quality solutions to large multiagent planning and learning problems.
Scalable Bayesian Reinforcement Learning for Multiagent POMDPs
2013
Bayesian methods for reinforcement learning (RL) allow model uncertainty to be considered explicitly and offer a principled way of dealing with the exploration/exploitation tradeoff. However, for multiagent systems there have been few such approaches, and none of them apply to problems with state uncertainty. In this paper, we fill this gap by proposing a Bayesian RL framework for multiagent partially observable Markov decision processes that is able to take advantage of structure present in many problems. In this framework, a team of agents operates in a centralized fashion, but has uncertainty about the model of the environment. Fitting many real-world situations, we consider the case where agents learn the appropriate models while acting in an online fashion. Because it can quickly become intractable to choose the optimal action in naı̈ve versions of this online learning problem, we propose a more scalable approach based on samplebased search and factored value functions for the ...
Scalable Planning and Learning for Multiagent POMDPs
Online, sample-based planning algorithms for POMDPs have shown great promise in scaling to problems with large state spaces, but they become intractable for large action and observation spaces. This is particularly problematic in multiagent POMDPs where the action and observation space grows exponentially with the number of agents. To combat this intractability, we propose a novel scalable approach based on sample-based planning and factored value functions that exploits structure present in many multiagent settings. This approach applies not only in the planning case, but also in the Bayesian reinforcement learning setting. Experimental results show that we are able to provide high quality solutions to large multiagent planning and learning problems.
Graph-based Cross Entropy method for solving multi-robot decentralized POMDPs
2016 IEEE International Conference on Robotics and Automation (ICRA), 2016
This paper introduces a probabilistic algorithm for multi-robot decision-making under uncertainty, which can be posed as a Decentralized Partially Observable Markov Decision Process (Dec-POMDP). Dec-POMDPs are inherently synchronous decision-making frameworks which require significant computational resources to be solved, making them infeasible for many real-world robotics applications. The Decentralized Partially Observable Semi-Markov Decision Process (Dec-POSMDP) was recently introduced as an extension of the Dec-POMDP that uses high-level macro-actions to allow largescale, asynchronous decision-making. However, existing Dec-POSMDP solution methods have limited scalability or perform poorly as the problem size grows. This paper proposes a cross-entropy based Dec-POSMDP algorithm motivated by the combinatorial optimization literature. The algorithm is applied to a constrained package delivery domain, where it significantly outperforms existing Dec-POSMDP solution methods.
Open-Loop Plans in Multi-Robot POMDPs
2005
It is well known that it is much easier to find open-loop plans in partially-observable environments than it is to compute full policies. It is less well appreciated that open-loop plans can provide good (sometimes even optimal) performance in some real-world robotic planning problems. In this paper we identify several conditions under which open-loop plans provide good performance, and show that multi-agent tag (a recently-popular POMDP benchmark problem) satisfies these conditions. We take advantage of this result to ...
Agent Neighbourhood for Learning Approximated Policies in DEC-MDP
2007
Abstract Resolving multiagent team decision problems, where agents share a common goal, is challenging since the number of states and joint actions is exponential with the number of agents. Even if the resolution of such problems is theoretically possible via models such as DEC-MDP, it is often intractable. In this context, it is important to find a good approximated policy without high resolution complexity in the case of a team of agents.