• Accepted Paper

Pilot-guided deep reinforcement learning for navigation of a jellyfish-like swimmer in flows with obstacles

Yihao Chen and Yue Yang

Phys. Rev. Fluids - Accepted 15 September, 2026

DOI: https://doi.org/10.1103/g3qy-d7q7

Abstract

We develop a deep reinforcement learning framework for controlling a bio-inspired jellyfish swimmer to navigate complex fluid environments with obstacles. While existing DRL frameworks for underwater navigation often use only kinematic and geometric state representations (e.g., position, orientation, velocity, and proximity distances), a key challenge remains in achieving efficient obstacle avoidance under strong fluid-structure interactions and near-wall effects. We augment the agent’‘s state representation within a soft actor-critic algorithm to include the real-time forces and torque experienced by the swimmer, providing direct mechanical feedback from vortex-wall interactions. A path-planning module supplies a local pilot point along the computed shortest path to guide the swimmer, reducing the navigation task to reaching a nearby target while avoiding obstacles. This augmented state space enables the swimmer to perceive and interpret wall proximity and orientation through distinct hydrodynamic force signatures. We analyze how these force and torque patterns, generated by walls at different positions influence the swimmer’’s decision-making policy. Comparative experiments with a baseline model without force feedback demonstrate that the present one with force feedback achieves higher navigation efficiency in two-dimensional obstacle-avoidance tasks. The results show that explicit force feedback facilitates earlier, smoother maneuvers and enables the exploitation of wall effects for efficient turning behaviors. With an application to autonomous cave mapping, this work underscores the critical role of direct mechanical feedback in the reinforcement learning framework for improving navigation within complex fluid environments.

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