Abstract

The ability to remotely control a free-floating object through surface flows on a fluid medium can facilitate numerous applications. Current studies on this problem have been limited to uni-directional motion control due to the challenging nature of the control problem. Analytical modelling of the object dynamics is difficult due to the high-dimensionality and mixing of the surface flows while the control problem is hard due to the nonlinear slow dynamics of the fluid medium, underactuation, and chaotic regions. This study presents a methodology for manipulation of free-floating objects using large-scale physical experimentation and recent advances in deep reinforcement learning. We demonstrate our methodology through the open-loop control of a free-floating object in water using a robotic arm. Our learned control policy is relatively quick to obtain, highly data efficient, and easily scalable to a higher-dimensional parameter space and/or experimental scenarios. Our results show the potential of data-driven approaches for solving and analyzing highly complex nonlinear control problems.

Highlights

  • The ability to remotely control a free-floating object through surface flows on a fluid medium can facilitate numerous applications

  • This trade-off between unrepeatabilities of the trajectory and the target angles is observed with the deep deterministic policy gradient (DDPG) controller, implying that this is a fundamental limitation of the system itself

  • This study shows that deep learning techniques combined with large scale robotic experimentation can be used to develop effective controllers in the face of nonlinearities, non-convexity, and environmental stochasticity

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Summary

Introduction

The ability to remotely control a free-floating object through surface flows on a fluid medium can facilitate numerous applications. Current studies on this problem have been limited to uni-directional motion control due to the challenging nature of the control problem. The control objective is to generate surface flows on the fluid surface by parametrically excited high-dimensional local wave sources These create two-dimensional horizontal velocity fields at the surface, known as Faraday flows, that have attributes of two-dimensional turbulence; characterised by surface vortices and local Lagrangian coherent s­ tructures[4,9,10,11]. This work extends the state-of-the-art to the two-dimensional control of a floating object in water driven by multi-periodic wave sources using recent advances in deep reinforcement learning (DRL). An electromagnet is used to reset the object to a new starting position—see Experimental Setup and Supplementary Video 1

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