Optimum control strategies for maximum thrust production in underwater undulatory swimming

TL;DR

This paper explores optimal control strategies for maximizing thrust in biomimetic robotic swimmers by combining machine learning and fluid dynamics, leading to efficient autonomous underwater propulsion.

Contribution

It introduces a novel approach to identify control signals that optimize thrust without prior system knowledge, bridging biology, fluid dynamics, and robotics.

Findings

Optimal tail-beat frequency and amplitude identified

Control strategy validated through fluid-structure simulations

Method applicable for autonomous robotic underwater vehicles

Abstract

Fishes, cetaceans, and many other aquatic vertebrates undulate their bodies to propel themselves through water. Swimming requires an intricate interplay between sensing the environment, making decisions, controlling internal dynamics, and moving the body in interaction with the external medium. Within this sequence of actions initiating locomotion, biological and physical laws manifest complex and nonlinear effects, which does not prevent natural swimmers to demonstrate efficient movement. This raises two complementary questions: how to model this intricacy and how to abstract it for practical swimming. In the context of robotics, the second question is of paramount importance to build efficient artificial swimmers driven by digital signals and mechanics. In this study, we tackle these two questions by leveraging a biomimetic robotic swimmer as a platform for investigating optimal control strategies for thrust generation. Through a combination of machine learning techniques and intuitive models, we identify a control signal that maximizes thrust production. Optimum tail-beat frequency and amplitude result from the subtle interplay between the swimmer's internal dynamics and its interaction with the surrounding fluid. We then propose a practical implementation for autonomous robotic swimmers that requires no prior knowledge of systems or equations. Direct fluid-structure simulations confirms the effectiveness and reliability of the proposed approach. Hence, our findings bridge fluid dynamics, robotics, and biology, providing valuable insights into the physics of aquatic locomotion