Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path Planning

Coverage path planning (CPP) is the problem of finding a path that covers the entire free space of a confined area, with applications ranging from robotic lawn mowing to search-and-rescue. While for known environments, offline methods can find provably complete paths, and in some cases optimal solut...

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Main Authors: Arvi Jonnarth, Ola Johansson, Jie Zhao, Michael Felsberg
Format: Article
Language:English
Published: IEEE 2025-01-01
Series:IEEE Access
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Online Access:https://ieeexplore.ieee.org/document/11039829/
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author Arvi Jonnarth
Ola Johansson
Jie Zhao
Michael Felsberg
author_facet Arvi Jonnarth
Ola Johansson
Jie Zhao
Michael Felsberg
author_sort Arvi Jonnarth
collection DOAJ
description Coverage path planning (CPP) is the problem of finding a path that covers the entire free space of a confined area, with applications ranging from robotic lawn mowing to search-and-rescue. While for known environments, offline methods can find provably complete paths, and in some cases optimal solutions, unknown environments need to be planned online during mapping. We investigate the suitability of continuous-space reinforcement learning (RL) for this challenging problem, and propose a computationally feasible egocentric map representation based on frontiers, as well as a novel reward term based on total variation to promote complete coverage. Compared to existing classical methods, this approach allows for a flexible path space, and enables the agent to adapt to specific environment characteristics. Meanwhile, the deployment of RL models on real robot systems is difficult. Training from scratch may be infeasible due to slow convergence times, while transferring from simulation to reality, i.e. sim-to-real transfer, is a key challenge in itself. We bridge the sim-to-real gap through a semi-virtual environment, including a real robot and real-time aspects, while utilizing a simulated sensor and obstacles to enable environment randomization and automated episode resetting. We investigate what level of fine-tuning is needed for adapting to a realistic setting. Through extensive experiments, we show that our approach surpasses the performance of both previous RL-based approaches and highly specialized methods across multiple CPP variations in simulation. Meanwhile, our method successfully transfers to a real robot. Our code implementation can be found online (Link to code repository: <uri>https://github.com/arvijj/rl-cpp</uri>).
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issn 2169-3536
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publishDate 2025-01-01
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spelling doaj-art-e1d1508810ca4149b15daa34c5f91f142025-08-20T03:24:06ZengIEEEIEEE Access2169-35362025-01-011310688310690510.1109/ACCESS.2025.358103511039829Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path PlanningArvi Jonnarth0https://orcid.org/0000-0002-3434-2522Ola Johansson1https://orcid.org/0009-0001-1386-3230Jie Zhao2https://orcid.org/0000-0002-3924-5537Michael Felsberg3https://orcid.org/0000-0002-6096-3648Manta Systems, Link&#x00F6;ping, SwedenDepartment of Electrical Engineering, Link&#x00F6;ping University, Link&#x00F6;ping, SwedenDepartment of Information and Communication Engineering, Dalian University of Technology, Dalian, ChinaDepartment of Electrical Engineering, Link&#x00F6;ping University, Link&#x00F6;ping, SwedenCoverage path planning (CPP) is the problem of finding a path that covers the entire free space of a confined area, with applications ranging from robotic lawn mowing to search-and-rescue. While for known environments, offline methods can find provably complete paths, and in some cases optimal solutions, unknown environments need to be planned online during mapping. We investigate the suitability of continuous-space reinforcement learning (RL) for this challenging problem, and propose a computationally feasible egocentric map representation based on frontiers, as well as a novel reward term based on total variation to promote complete coverage. Compared to existing classical methods, this approach allows for a flexible path space, and enables the agent to adapt to specific environment characteristics. Meanwhile, the deployment of RL models on real robot systems is difficult. Training from scratch may be infeasible due to slow convergence times, while transferring from simulation to reality, i.e. sim-to-real transfer, is a key challenge in itself. We bridge the sim-to-real gap through a semi-virtual environment, including a real robot and real-time aspects, while utilizing a simulated sensor and obstacles to enable environment randomization and automated episode resetting. We investigate what level of fine-tuning is needed for adapting to a realistic setting. Through extensive experiments, we show that our approach surpasses the performance of both previous RL-based approaches and highly specialized methods across multiple CPP variations in simulation. Meanwhile, our method successfully transfers to a real robot. Our code implementation can be found online (Link to code repository: <uri>https://github.com/arvijj/rl-cpp</uri>).https://ieeexplore.ieee.org/document/11039829/Coverage path planningend-to-end learningexplorationonlinereal-timereinforcement learning
spellingShingle Arvi Jonnarth
Ola Johansson
Jie Zhao
Michael Felsberg
Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path Planning
IEEE Access
Coverage path planning
end-to-end learning
exploration
online
real-time
reinforcement learning
title Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path Planning
title_full Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path Planning
title_fullStr Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path Planning
title_full_unstemmed Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path Planning
title_short Sim-to-Real Transfer of Deep Reinforcement Learning Agents for Online Coverage Path Planning
title_sort sim to real transfer of deep reinforcement learning agents for online coverage path planning
topic Coverage path planning
end-to-end learning
exploration
online
real-time
reinforcement learning
url https://ieeexplore.ieee.org/document/11039829/
work_keys_str_mv AT arvijonnarth simtorealtransferofdeepreinforcementlearningagentsforonlinecoveragepathplanning
AT olajohansson simtorealtransferofdeepreinforcementlearningagentsforonlinecoveragepathplanning
AT jiezhao simtorealtransferofdeepreinforcementlearningagentsforonlinecoveragepathplanning
AT michaelfelsberg simtorealtransferofdeepreinforcementlearningagentsforonlinecoveragepathplanning